Put the optimizations into their own list.

[rsync.git] / rsync.1.md

# NAME

rsync - a fast, versatile, remote (and local) file-copying tool

# SYNOPSIS

```
Local:
    rsync [OPTION...] SRC... [DEST]

Access via remote shell:
    Pull:
        rsync [OPTION...] [USER@]HOST:SRC... [DEST]
    Push:
        rsync [OPTION...] SRC... [USER@]HOST:DEST

Access via rsync daemon:
    Pull:
        rsync [OPTION...] [USER@]HOST::SRC... [DEST]
        rsync [OPTION...] rsync://[USER@]HOST[:PORT]/SRC... [DEST]
    Push:
        rsync [OPTION...] SRC... [USER@]HOST::DEST
        rsync [OPTION...] SRC... rsync://[USER@]HOST[:PORT]/DEST)
```

Usages with just one SRC arg and no DEST arg will list the source files instead
of copying.

# DESCRIPTION

Rsync is a fast and extraordinarily versatile file copying tool.  It can copy
locally, to/from another host over any remote shell, or to/from a remote rsync
daemon.  It offers a large number of options that control every aspect of its
behavior and permit very flexible specification of the set of files to be
copied.  It is famous for its delta-transfer algorithm, which reduces the
amount of data sent over the network by sending only the differences between
the source files and the existing files in the destination.  Rsync is widely
used for backups and mirroring and as an improved copy command for everyday
use.

Rsync finds files that need to be transferred using a "quick check" algorithm
(by default) that looks for files that have changed in size or in last-modified
time.  Any changes in the other preserved attributes (as requested by options)
are made on the destination file directly when the quick check indicates that
the file's data does not need to be updated.

Some of the additional features of rsync are:

- support for copying links, devices, owners, groups, and permissions
- exclude and exclude-from options similar to GNU tar
- a CVS exclude mode for ignoring the same files that CVS would ignore
- can use any transparent remote shell, including ssh or rsh
- does not require super-user privileges
- pipelining of file transfers to minimize latency costs
- support for anonymous or authenticated rsync daemons (ideal for mirroring)

# GENERAL

Rsync copies files either to or from a remote host, or locally on the current
host (it does not support copying files between two remote hosts).

There are two different ways for rsync to contact a remote system: using a
remote-shell program as the transport (such as ssh or rsh) or contacting an
rsync daemon directly via TCP.  The remote-shell transport is used whenever the
source or destination path contains a single colon (:) separator after a host
specification.  Contacting an rsync daemon directly happens when the source or
destination path contains a double colon (::) separator after a host
specification, OR when an rsync:// URL is specified (see also the "USING
RSYNC-DAEMON FEATURES VIA A REMOTE-SHELL CONNECTION" section for an exception
to this latter rule).

As a special case, if a single source arg is specified without a destination,
the files are listed in an output format similar to "`ls -l`".

As expected, if neither the source or destination path specify a remote host,
the copy occurs locally (see also the `--list-only` option).

Rsync refers to the local side as the client and the remote side as the server.
Don't confuse server with an rsync daemon.  A daemon is always a server, but a
server can be either a daemon or a remote-shell spawned process.

# SETUP

See the file README.md for installation instructions.

Once installed, you can use rsync to any machine that you can access via a
remote shell (as well as some that you can access using the rsync daemon-mode
protocol).  For remote transfers, a modern rsync uses ssh for its
communications, but it may have been configured to use a different remote shell
by default, such as rsh or remsh.

You can also specify any remote shell you like, either by using the `-e`
command line option, or by setting the RSYNC_RSH environment variable.

Note that rsync must be installed on both the source and destination machines.

# USAGE

You use rsync in the same way you use rcp.  You must specify a source and a
destination, one of which may be remote.

Perhaps the best way to explain the syntax is with some examples:

>     rsync -t *.c foo:src/

This would transfer all files matching the pattern `*.c` from the current
directory to the directory src on the machine foo.  If any of the files already
exist on the remote system then the rsync remote-update protocol is used to
update the file by sending only the differences in the data.  Note that the
expansion of wildcards on the commandline (`*.c`) into a list of files is
handled by the shell before it runs rsync and not by rsync itself (exactly the
same as all other posix-style programs).

>     rsync -avz foo:src/bar /data/tmp

This would recursively transfer all files from the directory src/bar on the
machine foo into the /data/tmp/bar directory on the local machine.  The files
are transferred in archive mode, which ensures that symbolic links, devices,
attributes, permissions, ownerships, etc. are preserved in the transfer.
Additionally, compression will be used to reduce the size of data portions of
the transfer.

>     rsync -avz foo:src/bar/ /data/tmp

A trailing slash on the source changes this behavior to avoid creating an
additional directory level at the destination.  You can think of a trailing /
on a source as meaning "copy the contents of this directory" as opposed to
"copy the directory by name", but in both cases the attributes of the
containing directory are transferred to the containing directory on the
destination.  In other words, each of the following commands copies the files
in the same way, including their setting of the attributes of /dest/foo:

>     rsync -av /src/foo /dest
>     rsync -av /src/foo/ /dest/foo

Note also that host and module references don't require a trailing slash to
copy the contents of the default directory.  For example, both of these copy
the remote directory's contents into "/dest":

>     rsync -av host: /dest
>     rsync -av host::module /dest

You can also use rsync in local-only mode, where both the source and
destination don't have a ':' in the name.  In this case it behaves like an
improved copy command.

Finally, you can list all the (listable) modules available from a particular
rsync daemon by leaving off the module name:

>     rsync somehost.mydomain.com::

See the following section for more details.

# ADVANCED USAGE

The syntax for requesting multiple files from a remote host is done by
specifying additional remote-host args in the same style as the first, or with
the hostname omitted.  For instance, all these work:

>     rsync -av host:file1 :file2 host:file{3,4} /dest/
>     rsync -av host::modname/file{1,2} host::modname/file3 /dest/
>     rsync -av host::modname/file1 ::modname/file{3,4}

Older versions of rsync required using quoted spaces in the SRC, like these
examples:

>     rsync -av host:'dir1/file1 dir2/file2' /dest
>     rsync host::'modname/dir1/file1 modname/dir2/file2' /dest

This word-splitting still works (by default) in the latest rsync, but is not as
easy to use as the first method.

If you need to transfer a filename that contains whitespace, you can either
specify the `--protect-args` (`-s`) option, or you'll need to escape the
whitespace in a way that the remote shell will understand.  For instance:

>     rsync -av host:'file\ name\ with\ spaces' /dest

# CONNECTING TO AN RSYNC DAEMON

It is also possible to use rsync without a remote shell as the transport.  In
this case you will directly connect to a remote rsync daemon, typically using
TCP port 873. (This obviously requires the daemon to be running on the remote
system, so refer to the STARTING AN RSYNC DAEMON TO ACCEPT CONNECTIONS section
below for information on that.)

Using rsync in this way is the same as using it with a remote shell except
that:

- you either use a double colon :: instead of a single colon to separate the
  hostname from the path, or you use an rsync:// URL.
- the first word of the "path" is actually a module name.
- the remote daemon may print a message of the day when you connect.
- if you specify no path name on the remote daemon then the list of accessible
  paths on the daemon will be shown.
- if you specify no local destination then a listing of the specified files on
  the remote daemon is provided.
- you must not specify the `--rsh` (`-e`) option (since that overrides the
  daemon connection to use ssh -- see USING RSYNC-DAEMON FEATURES VIA A
  REMOTE-SHELL CONNECTION below).

An example that copies all the files in a remote module named "src":

>     rsync -av host::src /dest

Some modules on the remote daemon may require authentication.  If so, you will
receive a password prompt when you connect.  You can avoid the password prompt
by setting the environment variable RSYNC_PASSWORD to the password you want to
use or using the `--password-file` option.  This may be useful when scripting
rsync.

WARNING: On some systems environment variables are visible to all users.  On
those systems using `--password-file` is recommended.

You may establish the connection via a web proxy by setting the environment
variable RSYNC_PROXY to a hostname:port pair pointing to your web proxy.  Note
that your web proxy's configuration must support proxy connections to port 873.

You may also establish a daemon connection using a program as a proxy by
setting the environment variable RSYNC_CONNECT_PROG to the commands you wish to
run in place of making a direct socket connection.  The string may contain the
escape "%H" to represent the hostname specified in the rsync command (so use
"%%" if you need a single "%" in your string).  For example:

>     export RSYNC_CONNECT_PROG='ssh proxyhost nc %H 873'
>     rsync -av targethost1::module/src/ /dest/
>     rsync -av rsync://targethost2/module/src/ /dest/

The command specified above uses ssh to run nc (netcat) on a proxyhost, which
forwards all data to port 873 (the rsync daemon) on the targethost (%H).

Note also that if the RSYNC_SHELL environment variable is set, that program
will be used to run the RSYNC_CONNECT_PROG command instead of using the default
shell of the **system()** call.

# USING RSYNC-DAEMON FEATURES VIA A REMOTE-SHELL CONNECTION

It is sometimes useful to use various features of an rsync daemon (such as
named modules) without actually allowing any new socket connections into a
system (other than what is already required to allow remote-shell access).
Rsync supports connecting to a host using a remote shell and then spawning a
single-use "daemon" server that expects to read its config file in the home dir
of the remote user.  This can be useful if you want to encrypt a daemon-style
transfer's data, but since the daemon is started up fresh by the remote user,
you may not be able to use features such as chroot or change the uid used by
the daemon. (For another way to encrypt a daemon transfer, consider using ssh
to tunnel a local port to a remote machine and configure a normal rsync daemon
on that remote host to only allow connections from "localhost".)

From the user's perspective, a daemon transfer via a remote-shell connection
uses nearly the same command-line syntax as a normal rsync-daemon transfer,
with the only exception being that you must explicitly set the remote shell
program on the command-line with the `--rsh=COMMAND` option. (Setting the
RSYNC_RSH in the environment will not turn on this functionality.) For example:

>     rsync -av --rsh=ssh host::module /dest

If you need to specify a different remote-shell user, keep in mind that the
user@ prefix in front of the host is specifying the rsync-user value (for a
module that requires user-based authentication).  This means that you must give
the '-l user' option to ssh when specifying the remote-shell, as in this
example that uses the short version of the `--rsh` option:

>     rsync -av -e "ssh -l ssh-user" rsync-user@host::module /dest

The "ssh-user" will be used at the ssh level; the "rsync-user" will be used to
log-in to the "module".

# STARTING AN RSYNC DAEMON TO ACCEPT CONNECTIONS

In order to connect to an rsync daemon, the remote system needs to have a
daemon already running (or it needs to have configured something like inetd to
spawn an rsync daemon for incoming connections on a particular port).  For full
information on how to start a daemon that will handling incoming socket
connections, see the **rsyncd.conf**(5) man page -- that is the config file for
the daemon, and it contains the full details for how to run the daemon
(including stand-alone and inetd configurations).

If you're using one of the remote-shell transports for the transfer, there is
no need to manually start an rsync daemon.

# SORTED TRANSFER ORDER

Rsync always sorts the specified filenames into its internal transfer list.
This handles the merging together of the contents of identically named
directories, makes it easy to remove duplicate filenames, and may confuse
someone when the files are transferred in a different order than what was given
on the command-line.

If you need a particular file to be transferred prior to another, either
separate the files into different rsync calls, or consider using
`--delay-updates` (which doesn't affect the sorted transfer order, but does
make the final file-updating phase happen much more rapidly).

# EXAMPLES

Here are some examples of how I use rsync.

To backup my wife's home directory, which consists of large MS Word files and
mail folders, I use a cron job that runs

>     rsync -Cavz . arvidsjaur:backup

each night over a PPP connection to a duplicate directory on my machine
"arvidsjaur".

To synchronize my samba source trees I use the following Makefile targets:

>     get:
>         rsync -avuzb --exclude '*~' samba:samba/ .
>     put:
>         rsync -Cavuzb . samba:samba/
>     sync: get put

This allows me to sync with a CVS directory at the other end of the connection.
I then do CVS operations on the remote machine, which saves a lot of time as
the remote CVS protocol isn't very efficient.

I mirror a directory between my "old" and "new" ftp sites with the command:

>     rsync -az -e ssh --delete ~ftp/pub/samba nimbus:"~ftp/pub/tridge"

This is launched from cron every few hours.

# OPTION SUMMARY

Here is a short summary of the options available in rsync.  Please refer to the
detailed description below for a complete description.

[comment]: # (help-rsync.h)
[comment]: # (Keep these short enough that they'll be under 80 chars when indented by 8 chars.)

```
--verbose, -v            increase verbosity
--info=FLAGS             fine-grained informational verbosity
--debug=FLAGS            fine-grained debug verbosity
--msgs2stderr            output messages directly to stderr
--quiet, -q              suppress non-error messages
--no-motd                suppress daemon-mode MOTD
--checksum, -c           skip based on checksum, not mod-time & size
--archive, -a            archive mode; equals -rlptgoD (no -H,-A,-X)
--no-OPTION              turn off an implied OPTION (e.g. --no-D)
--recursive, -r          recurse into directories
--relative, -R           use relative path names
--no-implied-dirs        don't send implied dirs with --relative
--backup, -b             make backups (see --suffix & --backup-dir)
--backup-dir=DIR         make backups into hierarchy based in DIR
--suffix=SUFFIX          backup suffix (default ~ w/o --backup-dir)
--update, -u             skip files that are newer on the receiver
--inplace                update destination files in-place
--append                 append data onto shorter files
--append-verify          --append w/old data in file checksum
--dirs, -d               transfer directories without recursing
--links, -l              copy symlinks as symlinks
--copy-links, -L         transform symlink into referent file/dir
--copy-unsafe-links      only "unsafe" symlinks are transformed
--safe-links             ignore symlinks that point outside the tree
--munge-links            munge symlinks to make them safe & unusable
--copy-dirlinks, -k      transform symlink to dir into referent dir
--keep-dirlinks, -K      treat symlinked dir on receiver as dir
--hard-links, -H         preserve hard links
--perms, -p              preserve permissions
--executability, -E      preserve executability
--chmod=CHMOD            affect file and/or directory permissions
--acls, -A               preserve ACLs (implies --perms)
--xattrs, -X             preserve extended attributes
--owner, -o              preserve owner (super-user only)
--group, -g              preserve group
--devices                preserve device files (super-user only)
--specials               preserve special files
-D                       same as --devices --specials
--times, -t              preserve modification times
--atimes, -U             preserve access (use) times
--open-noatime           avoid changing the atime on opened files
--omit-dir-times, -O     omit directories from --times
--omit-link-times, -J    omit symlinks from --times
--super                  receiver attempts super-user activities
--fake-super             store/recover privileged attrs using xattrs
--sparse, -S             turn sequences of nulls into sparse blocks
--preallocate            allocate dest files before writing them
--write-devices          write to devices as files (implies --inplace)
--dry-run, -n            perform a trial run with no changes made
--whole-file, -W         copy files whole (w/o delta-xfer algorithm)
--checksum-choice=STR    choose the checksum algorithm (aka --cc)
--one-file-system, -x    don't cross filesystem boundaries
--block-size=SIZE, -B    force a fixed checksum block-size
--rsh=COMMAND, -e        specify the remote shell to use
--rsync-path=PROGRAM     specify the rsync to run on remote machine
--existing               skip creating new files on receiver
--ignore-existing        skip updating files that exist on receiver
--remove-source-files    sender removes synchronized files (non-dir)
--del                    an alias for --delete-during
--delete                 delete extraneous files from dest dirs
--delete-before          receiver deletes before xfer, not during
--delete-during          receiver deletes during the transfer
--delete-delay           find deletions during, delete after
--delete-after           receiver deletes after transfer, not during
--delete-excluded        also delete excluded files from dest dirs
--ignore-missing-args    ignore missing source args without error
--delete-missing-args    delete missing source args from destination
--ignore-errors          delete even if there are I/O errors
--force                  force deletion of dirs even if not empty
--max-delete=NUM         don't delete more than NUM files
--max-size=SIZE          don't transfer any file larger than SIZE
--min-size=SIZE          don't transfer any file smaller than SIZE
--max-alloc=SIZE         change a limit relating to memory alloc
--partial                keep partially transferred files
--partial-dir=DIR        put a partially transferred file into DIR
--delay-updates          put all updated files into place at end
--prune-empty-dirs, -m   prune empty directory chains from file-list
--numeric-ids            don't map uid/gid values by user/group name
--usermap=STRING         custom username mapping
--groupmap=STRING        custom groupname mapping
--chown=USER:GROUP       simple username/groupname mapping
--timeout=SECONDS        set I/O timeout in seconds
--contimeout=SECONDS     set daemon connection timeout in seconds
--ignore-times, -I       don't skip files that match size and time
--size-only              skip files that match in size
--modify-window=NUM, -@  set the accuracy for mod-time comparisons
--temp-dir=DIR, -T       create temporary files in directory DIR
--fuzzy, -y              find similar file for basis if no dest file
--compare-dest=DIR       also compare destination files relative to DIR
--copy-dest=DIR          ... and include copies of unchanged files
--link-dest=DIR          hardlink to files in DIR when unchanged
--compress, -z           compress file data during the transfer
--compress-choice=STR    choose the compression algorithm (aka --zc)
--compress-level=NUM     explicitly set compression level (aka --zl)
--skip-compress=LIST     skip compressing files with suffix in LIST
--cvs-exclude, -C        auto-ignore files in the same way CVS does
--filter=RULE, -f        add a file-filtering RULE
-F                       same as --filter='dir-merge /.rsync-filter'
                         repeated: --filter='- .rsync-filter'
--exclude=PATTERN        exclude files matching PATTERN
--exclude-from=FILE      read exclude patterns from FILE
--include=PATTERN        don't exclude files matching PATTERN
--include-from=FILE      read include patterns from FILE
--files-from=FILE        read list of source-file names from FILE
--from0, -0              all *-from/filter files are delimited by 0s
--protect-args, -s       no space-splitting; wildcard chars only
--copy-as=USER[:GROUP]   specify user & optional group for the copy
--address=ADDRESS        bind address for outgoing socket to daemon
--port=PORT              specify double-colon alternate port number
--sockopts=OPTIONS       specify custom TCP options
--blocking-io            use blocking I/O for the remote shell
--outbuf=N|L|B           set out buffering to None, Line, or Block
--stats                  give some file-transfer stats
--8-bit-output, -8       leave high-bit chars unescaped in output
--human-readable, -h     output numbers in a human-readable format
--progress               show progress during transfer
-P                       same as --partial --progress
--itemize-changes, -i    output a change-summary for all updates
--remote-option=OPT, -M  send OPTION to the remote side only
--out-format=FORMAT      output updates using the specified FORMAT
--log-file=FILE          log what we're doing to the specified FILE
--log-file-format=FMT    log updates using the specified FMT
--password-file=FILE     read daemon-access password from FILE
--early-input=FILE       use FILE for daemon's early exec input
--list-only              list the files instead of copying them
--bwlimit=RATE           limit socket I/O bandwidth
--write-batch=FILE       write a batched update to FILE
--only-write-batch=FILE  like --write-batch but w/o updating dest
--read-batch=FILE        read a batched update from FILE
--protocol=NUM           force an older protocol version to be used
--iconv=CONVERT_SPEC     request charset conversion of filenames
--checksum-seed=NUM      set block/file checksum seed (advanced)
--ipv4, -4               prefer IPv4
--ipv6, -6               prefer IPv6
--version, -V            print the version + other info and exit
--help, -h (*)           show this help (* -h is help only on its own)
```

Rsync can also be run as a daemon, in which case the following options are
accepted:

[comment]: # (help-rsyncd.h)

```
--daemon                 run as an rsync daemon
--address=ADDRESS        bind to the specified address
--bwlimit=RATE           limit socket I/O bandwidth
--config=FILE            specify alternate rsyncd.conf file
--dparam=OVERRIDE, -M    override global daemon config parameter
--no-detach              do not detach from the parent
--port=PORT              listen on alternate port number
--log-file=FILE          override the "log file" setting
--log-file-format=FMT    override the "log format" setting
--sockopts=OPTIONS       specify custom TCP options
--verbose, -v            increase verbosity
--ipv4, -4               prefer IPv4
--ipv6, -6               prefer IPv6
--help, -h               show this help (when used with --daemon)
```

# OPTIONS

Rsync accepts both long (double-dash + word) and short (single-dash + letter)
options.  The full list of the available options are described below.  If an
option can be specified in more than one way, the choices are comma-separated.
Some options only have a long variant, not a short.  If the option takes a
parameter, the parameter is only listed after the long variant, even though it
must also be specified for the short.  When specifying a parameter, you can
either use the form `--option=param` or replace the '=' with whitespace.  The
parameter may need to be quoted in some manner for it to survive the shell's
command-line parsing.  Keep in mind that a leading tilde (`~`) in a filename is
substituted by your shell, so `--option=~/foo` will not change the tilde into
your home directory (remove the '=' for that).

[comment]: # (An OL starting at 0 is converted into a DL by the parser.)

0.  `--help`, `-h` `(*)`

    Print a short help page describing the options available in rsync and exit.
    (*) The `-h` short option will only invoke `--help` when used without other
    options since it normally means `--human-readable`.

0.  `--version`, `-V`

    Print the rsync version plus other info and exit.

    The output includes the default list of checksum algorithms, the default
    list of compression algorithms, a list of compiled-in capabilities, a link
    to the rsync web site, and some license/copyright info.

0.  `--verbose`, `-v`

    This option increases the amount of information you are given during the
    transfer.  By default, rsync works silently.  A single `-v` will give you
    information about what files are being transferred and a brief summary at
    the end.  Two `-v` options will give you information on what files are
    being skipped and slightly more information at the end.  More than two `-v`
    options should only be used if you are debugging rsync.

    In a modern rsync, the `-v` option is equivalent to the setting of groups
    of `--info` and `--debug` options.  You can choose to use these newer
    options in addition to, or in place of using `--verbose`, as any
    fine-grained settings override the implied settings of `-v`.  Both `--info`
    and `--debug` have a way to ask for help that tells you exactly what flags
    are set for each increase in verbosity.

    However, do keep in mind that a daemon's "`max verbosity`" setting will limit
    how high of a level the various individual flags can be set on the daemon
    side.  For instance, if the max is 2, then any info and/or debug flag that
    is set to a higher value than what would be set by `-vv` will be downgraded
    to the `-vv` level in the daemon's logging.

0.  `--info=FLAGS`

    This option lets you have fine-grained control over the information output
    you want to see.  An individual flag name may be followed by a level
    number, with 0 meaning to silence that output, 1 being the default output
    level, and higher numbers increasing the output of that flag (for those
    that support higher levels).  Use `--info=help` to see all the available
    flag names, what they output, and what flag names are added for each
    increase in the verbose level.  Some examples:

    >     rsync -a --info=progress2 src/ dest/
    >     rsync -avv --info=stats2,misc1,flist0 src/ dest/

    Note that `--info=name`'s output is affected by the `--out-format` and
    `--itemize-changes` (`-i`) options.  See those options for more information
    on what is output and when.

    This option was added to 3.1.0, so an older rsync on the server side might
    reject your attempts at fine-grained control (if one or more flags needed
    to be send to the server and the server was too old to understand them).
    See also the "`max verbosity`" caveat above when dealing with a daemon.

0.  `--debug=FLAGS`

    This option lets you have fine-grained control over the debug output you
    want to see.  An individual flag name may be followed by a level number,
    with 0 meaning to silence that output, 1 being the default output level,
    and higher numbers increasing the output of that flag (for those that
    support higher levels).  Use `--debug=help` to see all the available flag
    names, what they output, and what flag names are added for each increase in
    the verbose level.  Some examples:

    >     rsync -avvv --debug=none src/ dest/
    >     rsync -avA --del --debug=del2,acl src/ dest/

    Note that some debug messages will only be output when `--msgs2stderr` is
    specified, especially those pertaining to I/O and buffer debugging.

    Beginning in 3.2.0, this option is no longer auto-forwared to the server
    side in order to allow you to specify different debug values for each side
    of the transfer, as well as to specify a new debug option that is only
    present in one of the rsync versions.  If you want to duplicate the same
    option on both sides, using brace expansion is an easy way to save you some
    typing.  This works in zsh and bash:

    >     rsync -aiv {-M,}--debug=del2 src/ dest/

0.  `--msgs2stderr`

    This option changes rsync to send all its output directly to stderr rather
    than to send messages to the client side via the protocol.  The protocol
    allows rsync to output normal messages via stdout and errors via stderr,
    but it can delay messages behind a slew of data.

    One case where this is helpful is when sending really large files, since
    errors that happen on a remote receiver tend to get delayed until after the
    file's data is fully sent.  It is also helpful for debugging, since it
    helps to avoid overpopulating the protocol data with extra message data.

    The option does not affect the remote side of a transfer without using
    `--remote-option`, e.g. `-M--msgs2stderr` or `{-M,}--msgs2stderr`.

    Also keep in mind that connecting to a normal (non-remote-shell) daemon
    does not have a stderr channel to send messages back to the client side, so
    a modern rsync only allows the option on a remote-shell-run daemon.

    This option has the side-effect of making stderr output get line-buffered
    so that the merging of the output of 3 programs happens in a more readable
    manner.

0.  `--quiet`, `-q`

    This option decreases the amount of information you are given during the
    transfer, notably suppressing information messages from the remote server.
    This option is useful when invoking rsync from cron.

0.  `--no-motd`

    This option affects the information that is output by the client at the
    start of a daemon transfer.  This suppresses the message-of-the-day (MOTD)
    text, but it also affects the list of modules that the daemon sends in
    response to the "rsync host::" request (due to a limitation in the rsync
    protocol), so omit this option if you want to request the list of modules
    from the daemon.

0.  `--ignore-times`, `-I`

    Normally rsync will skip any files that are already the same size and have
    the same modification timestamp.  This option turns off this "quick check"
    behavior, causing all files to be updated.

0.  `--size-only`

    This modifies rsync's "quick check" algorithm for finding files that need
    to be transferred, changing it from the default of transferring files with
    either a changed size or a changed last-modified time to just looking for
    files that have changed in size.  This is useful when starting to use rsync
    after using another mirroring system which may not preserve timestamps
    exactly.

0.  `--modify-window=NUM`, `-@`

    When comparing two timestamps, rsync treats the timestamps as being equal
    if they differ by no more than the modify-window value.  The default is 0,
    which matches just integer seconds.  If you specify a negative value (and
    the receiver is at least version 3.1.3) then nanoseconds will also be taken
    into account.  Specifying 1 is useful for copies to/from MS Windows FAT
    filesystems, because FAT represents times with a 2-second resolution
    (allowing times to differ from the original by up to 1 second).

    If you want all your transfers to default to comparing nanoseconds, you can
    create a `~/.popt` file and put these lines in it:

    >     rsync alias -a -a@-1
    >     rsync alias -t -t@-1

    With that as the default, you'd need to specify `--modify-window=0` (aka
    `-@0`) to override it and ignore nanoseconds, e.g. if you're copying
    between ext3 and ext4, or if the receiving rsync is older than 3.1.3.

0.  `--checksum`, `-c`

    This changes the way rsync checks if the files have been changed and are in
    need of a transfer.  Without this option, rsync uses a "quick check" that
    (by default) checks if each file's size and time of last modification match
    between the sender and receiver.  This option changes this to compare a
    128-bit checksum for each file that has a matching size.  Generating the
    checksums means that both sides will expend a lot of disk I/O reading all
    the data in the files in the transfer, so this can slow things down
    significantly (and this is prior to any reading that will be done to
    transfer changed files)

    The sending side generates its checksums while it is doing the file-system
    scan that builds the list of the available files.  The receiver generates
    its checksums when it is scanning for changed files, and will checksum any
    file that has the same size as the corresponding sender's file: files with
    either a changed size or a changed checksum are selected for transfer.

    Note that rsync always verifies that each _transferred_ file was correctly
    reconstructed on the receiving side by checking a whole-file checksum that
    is generated as the file is transferred, but that automatic
    after-the-transfer verification has nothing to do with this option's
    before-the-transfer "Does this file need to be updated?" check.

    The checksum used is auto-negotiated between the client and the server, but
    can be overridden using either the `--checksum-choice` option or an
    environment variable that is discussed in that option's section.

0.  `--archive`, `-a`

    This is equivalent to `-rlptgoD`.  It is a quick way of saying you want
    recursion and want to preserve almost everything (with `-H` being a notable
    omission).  The only exception to the above equivalence is when
    `--files-from` is specified, in which case `-r` is not implied.

    Note that `-a` **does not preserve hardlinks**, because finding
    multiply-linked files is expensive.  You must separately specify `-H`.

0.  `--no-OPTION`

    You may turn off one or more implied options by prefixing the option name
    with "no-".  Not all options may be prefixed with a "no-": only options that
    are implied by other options (e.g. `--no-D`, `--no-perms`) or have
    different defaults in various circumstances (e.g. `--no-whole-file`,
    `--no-blocking-io`, `--no-dirs`).  You may specify either the short or the
    long option name after the "no-" prefix (e.g. `--no-R` is the same as
    `--no-relative`).

    For example: if you want to use `-a` (`--archive`) but don't want `-o`
    (`--owner`), instead of converting `-a` into `-rlptgD`, you could specify
    `-a --no-o` (or `-a --no-owner`).

    The order of the options is important: if you specify `--no-r -a`, the
    `-r` option would end up being turned on, the opposite of `-a --no-r`.
    Note also that the side-effects of the `--files-from` option are NOT
    positional, as it affects the default state of several options and slightly
    changes the meaning of `-a` (see the `--files-from` option for more
    details).

0.  `--recursive`, `-r`

    This tells rsync to copy directories recursively.  See also `--dirs` (`-d`).

    Beginning with rsync 3.0.0, the recursive algorithm used is now an
    incremental scan that uses much less memory than before and begins the
    transfer after the scanning of the first few directories have been
    completed.  This incremental scan only affects our recursion algorithm, and
    does not change a non-recursive transfer.  It is also only possible when
    both ends of the transfer are at least version 3.0.0.

    Some options require rsync to know the full file list, so these options
    disable the incremental recursion mode.  These include: `--delete-before`,
    `--delete-after`, `--prune-empty-dirs`, and `--delay-updates`.  Because of
    this, the default delete mode when you specify `--delete` is now
    `--delete-during` when both ends of the connection are at least 3.0.0 (use
    `--del` or `--delete-during` to request this improved deletion mode
    explicitly).  See also the `--delete-delay` option that is a better choice
    than using `--delete-after`.

    Incremental recursion can be disabled using the `--no-inc-recursive` option
    or its shorter `--no-i-r` alias.

0.  `--relative`, `-R`

    Use relative paths.  This means that the full path names specified on the
    command line are sent to the server rather than just the last parts of the
    filenames.  This is particularly useful when you want to send several
    different directories at the same time.  For example, if you used this
    command:

    >     rsync -av /foo/bar/baz.c remote:/tmp/

    would create a file named baz.c in /tmp/ on the remote machine.  If instead
    you used

    >     rsync -avR /foo/bar/baz.c remote:/tmp/

    then a file named /tmp/foo/bar/baz.c would be created on the remote
    machine, preserving its full path.  These extra path elements are called
    "implied directories" (i.e. the "foo" and the "foo/bar" directories in the
    above example).

    Beginning with rsync 3.0.0, rsync always sends these implied directories as
    real directories in the file list, even if a path element is really a
    symlink on the sending side.  This prevents some really unexpected behaviors
    when copying the full path of a file that you didn't realize had a symlink
    in its path.  If you want to duplicate a server-side symlink, include both
    the symlink via its path, and referent directory via its real path.  If
    you're dealing with an older rsync on the sending side, you may need to use
    the `--no-implied-dirs` option.

    It is also possible to limit the amount of path information that is sent as
    implied directories for each path you specify.  With a modern rsync on the
    sending side (beginning with 2.6.7), you can insert a dot and a slash into
    the source path, like this:

    >     rsync -avR /foo/./bar/baz.c remote:/tmp/

    That would create /tmp/bar/baz.c on the remote machine. (Note that the dot
    must be followed by a slash, so "/foo/." would not be abbreviated.) For
    older rsync versions, you would need to use a chdir to limit the source
    path.  For example, when pushing files:

    >     (cd /foo; rsync -avR bar/baz.c remote:/tmp/)

    (Note that the parens put the two commands into a sub-shell, so that the
    "cd" command doesn't remain in effect for future commands.) If you're
    pulling files from an older rsync, use this idiom (but only for a
    non-daemon transfer):

    >     rsync -avR --rsync-path="cd /foo; rsync" \
    >          remote:bar/baz.c /tmp/

0.  `--no-implied-dirs`

    This option affects the default behavior of the `--relative` option.  When
    it is specified, the attributes of the implied directories from the source
    names are not included in the transfer.  This means that the corresponding
    path elements on the destination system are left unchanged if they exist,
    and any missing implied directories are created with default attributes.
    This even allows these implied path elements to have big differences, such
    as being a symlink to a directory on the receiving side.

    For instance, if a command-line arg or a files-from entry told rsync to
    transfer the file "path/foo/file", the directories "path" and "path/foo"
    are implied when `--relative` is used.  If "path/foo" is a symlink to "bar"
    on the destination system, the receiving rsync would ordinarily delete
    "path/foo", recreate it as a directory, and receive the file into the new
    directory.  With `--no-implied-dirs`, the receiving rsync updates
    "path/foo/file" using the existing path elements, which means that the file
    ends up being created in "path/bar".  Another way to accomplish this link
    preservation is to use the `--keep-dirlinks` option (which will also affect
    symlinks to directories in the rest of the transfer).

    When pulling files from an rsync older than 3.0.0, you may need to use this
    option if the sending side has a symlink in the path you request and you
    wish the implied directories to be transferred as normal directories.

0.  `--backup`, `-b`

    With this option, preexisting destination files are renamed as each file is
    transferred or deleted.  You can control where the backup file goes and
    what (if any) suffix gets appended using the `--backup-dir` and `--suffix`
    options.

    Note that if you don't specify `--backup-dir`, (1) the `--omit-dir-times`
    option will be forced on, and (2) if `--delete` is also in effect (without
    `--delete-excluded`), rsync will add a "protect" filter-rule for the backup
    suffix to the end of all your existing excludes (e.g. `-f "P *~"`).  This
    will prevent previously backed-up files from being deleted.  Note that if
    you are supplying your own filter rules, you may need to manually insert
    your own exclude/protect rule somewhere higher up in the list so that it
    has a high enough priority to be effective (e.g., if your rules specify a
    trailing inclusion/exclusion of `*`, the auto-added rule would never be
    reached).

0.  `--backup-dir=DIR`

    This implies the `--backup` option, and tells rsync to store all
    backups in the specified directory on the receiving side.  This can be used
    for incremental backups.  You can additionally specify a backup suffix
    using the `--suffix` option (otherwise the files backed up in the specified
    directory will keep their original filenames).

    Note that if you specify a relative path, the backup directory will be
    relative to the destination directory, so you probably want to specify
    either an absolute path or a path that starts with "../".  If an rsync
    daemon is the receiver, the backup dir cannot go outside the module's path
    hierarchy, so take extra care not to delete it or copy into it.

0.  `--suffix=SUFFIX`

    This option allows you to override the default backup suffix used with the
    `--backup` (`-b`) option.  The default suffix is a `~` if no `--backup-dir`
    was specified, otherwise it is an empty string.

0.  `--update`, `-u`

    This forces rsync to skip any files which exist on the destination and have
    a modified time that is newer than the source file. (If an existing
    destination file has a modification time equal to the source file's, it
    will be updated if the sizes are different.)

    Note that this does not affect the copying of dirs, symlinks, or other
    special files.  Also, a difference of file format between the sender and
    receiver is always considered to be important enough for an update, no
    matter what date is on the objects.  In other words, if the source has a
    directory where the destination has a file, the transfer would occur
    regardless of the timestamps.

    This option is a transfer rule, not an exclude, so it doesn't affect the
    data that goes into the file-lists, and thus it doesn't affect deletions.
    It just limits the files that the receiver requests to be transferred.

0.  `--inplace`

    This option changes how rsync transfers a file when its data needs to be
    updated: instead of the default method of creating a new copy of the file
    and moving it into place when it is complete, rsync instead writes the
    updated data directly to the destination file.

    This has several effects:

    - Hard links are not broken.  This means the new data will be visible
      through other hard links to the destination file.  Moreover, attempts to
      copy differing source files onto a multiply-linked destination file will
      result in a "tug of war" with the destination data changing back and
      forth.
    - In-use binaries cannot be updated (either the OS will prevent this from
      happening, or binaries that attempt to swap-in their data will misbehave
      or crash).
    - The file's data will be in an inconsistent state during the transfer and
      will be left that way if the transfer is interrupted or if an update
      fails.
    - A file that rsync cannot write to cannot be updated.  While a super user
      can update any file, a normal user needs to be granted write permission
      for the open of the file for writing to be successful.
    - The efficiency of rsync's delta-transfer algorithm may be reduced if some
      data in the destination file is overwritten before it can be copied to a
      position later in the file.  This does not apply if you use `--backup`,
      since rsync is smart enough to use the backup file as the basis file for
      the transfer.

    WARNING: you should not use this option to update files that are being
    accessed by others, so be careful when choosing to use this for a copy.

    This option is useful for transferring large files with block-based changes
    or appended data, and also on systems that are disk bound, not network
    bound.  It can also help keep a copy-on-write filesystem snapshot from
    diverging the entire contents of a file that only has minor changes.

    The option implies `--partial` (since an interrupted transfer does not
    delete the file), but conflicts with `--partial-dir` and `--delay-updates`.
    Prior to rsync 2.6.4 `--inplace` was also incompatible with
    `--compare-dest` and `--link-dest`.

0.  `--append`

    This causes rsync to update a file by appending data onto the end of the
    file, which presumes that the data that already exists on the receiving
    side is identical with the start of the file on the sending side.  If a
    file needs to be transferred and its size on the receiver is the same or
    longer than the size on the sender, the file is skipped.  This does not
    interfere with the updating of a file's non-content attributes (e.g.
    permissions, ownership, etc.) when the file does not need to be
    transferred, nor does it affect the updating of any non-regular files.
    Implies `--inplace`.

    The use of `--append` can be dangerous if you aren't 100% sure that the
    files that are longer have only grown by the appending of data onto the
    end.  You should thus use include/exclude/filter rules to ensure that such
    a transfer is only affecting files that you know to be growing via appended
    data.

0.  `--append-verify`

    This works just like the `--append` option, but the existing data on the
    receiving side is included in the full-file checksum verification step,
    which will cause a file to be resent if the final verification step fails
    (rsync uses a normal, non-appending `--inplace` transfer for the resend).
    It otherwise has the exact same caveats for files that have not grown
    larger, so don't use this for a general copy.

    Note: prior to rsync 3.0.0, the `--append` option worked like
    `--append-verify`, so if you are interacting with an older rsync (or the
    transfer is using a protocol prior to 30), specifying either append option
    will initiate an `--append-verify` transfer.

0.  `--dirs`, `-d`

    Tell the sending side to include any directories that are encountered.
    Unlike `--recursive`, a directory's contents are not copied unless the
    directory name specified is "." or ends with a trailing slash (e.g. ".",
    "dir/.", "dir/", etc.).  Without this option or the `--recursive` option,
    rsync will skip all directories it encounters (and output a message to that
    effect for each one).  If you specify both `--dirs` and `--recursive`,
    `--recursive` takes precedence.

    The `--dirs` option is implied by the `--files-from` option or the
    `--list-only` option (including an implied `--list-only` usage) if
    `--recursive` wasn't specified (so that directories are seen in the
    listing).  Specify `--no-dirs` (or `--no-d`) if you want to turn this off.

    There is also a backward-compatibility helper option, `--old-dirs` (or
    `--old-d`) that tells rsync to use a hack of `-r --exclude='/*/*'` to get
    an older rsync to list a single directory without recursing.

0.  `--links`, `-l`

    When symlinks are encountered, recreate the symlink on the destination.

0.  `--copy-links`, `-L`

    When symlinks are encountered, the item that they point to (the referent)
    is copied, rather than the symlink.  In older versions of rsync, this
    option also had the side-effect of telling the receiving side to follow
    symlinks, such as symlinks to directories.  In a modern rsync such as this
    one, you'll need to specify `--keep-dirlinks` (`-K`) to get this extra
    behavior.  The only exception is when sending files to an rsync that is too
    old to understand `-K` -- in that case, the `-L` option will still have the
    side-effect of `-K` on that older receiving rsync.

0.  `--copy-unsafe-links`

    This tells rsync to copy the referent of symbolic links that point outside
    the copied tree.  Absolute symlinks are also treated like ordinary files,
    and so are any symlinks in the source path itself when `--relative` is
    used.  This option has no additional effect if `--copy-links` was also
    specified.

    Note that the cut-off point is the top of the transfer, which is the part
    of the path that rsync isn't mentioning in the verbose output.  If you copy
    "/src/subdir" to "/dest/" then the "subdir" directory is a name inside the
    transfer tree, not the top of the transfer (which is /src) so it is legal
    for created relative symlinks to refer to other names inside the /src and
    /dest directories.  If you instead copy "/src/subdir/" (with a trailing
    slash) to "/dest/subdir" that would not allow symlinks to any files outside
    of "subdir".

0.  `--safe-links`

    This tells rsync to ignore any symbolic links which point outside the
    copied tree.  All absolute symlinks are also ignored. Using this option in
    conjunction with `--relative` may give unexpected results.

0.  `--munge-links`

    This option tells rsync to (1) modify all symlinks on the receiving side in
    a way that makes them unusable but recoverable (see below), or (2) to
    unmunge symlinks on the sending side that had been stored in a munged
    state.  This is useful if you don't quite trust the source of the data to
    not try to slip in a symlink to a unexpected place.

    The way rsync disables the use of symlinks is to prefix each one with the
    string "/rsyncd-munged/".  This prevents the links from being used as long
    as that directory does not exist.  When this option is enabled, rsync will
    refuse to run if that path is a directory or a symlink to a directory.

    The option only affects the client side of the transfer, so if you need it
    to affect the server, specify it via `--remote-option`. (Note that in a
    local transfer, the client side is the sender.)

    This option has no affect on a daemon, since the daemon configures whether
    it wants munged symlinks via its "`munge symlinks`" parameter.  See also the
    "munge-symlinks" perl script in the support directory of the source code.

0.  `--copy-dirlinks`, `-k`

    This option causes the sending side to treat a symlink to a directory as
    though it were a real directory.  This is useful if you don't want symlinks
    to non-directories to be affected, as they would be using `--copy-links`.

    Without this option, if the sending side has replaced a directory with a
    symlink to a directory, the receiving side will delete anything that is in
    the way of the new symlink, including a directory hierarchy (as long as
    `--force` or `--delete` is in effect).

    See also `--keep-dirlinks` for an analogous option for the receiving side.

    `--copy-dirlinks` applies to all symlinks to directories in the source.  If
    you want to follow only a few specified symlinks, a trick you can use is to
    pass them as additional source args with a trailing slash, using
    `--relative` to make the paths match up right.  For example:

    >     rsync -r --relative src/./ src/./follow-me/ dest/

    This works because rsync calls **lstat**(2) on the source arg as given, and
    the trailing slash makes **lstat**(2) follow the symlink, giving rise to a
    directory in the file-list which overrides the symlink found during the
    scan of "src/./".

0.  `--keep-dirlinks`, `-K`

    This option causes the receiving side to treat a symlink to a directory as
    though it were a real directory, but only if it matches a real directory
    from the sender.  Without this option, the receiver's symlink would be
    deleted and replaced with a real directory.

    For example, suppose you transfer a directory "foo" that contains a file
    "file", but "foo" is a symlink to directory "bar" on the receiver.  Without
    `--keep-dirlinks`, the receiver deletes symlink "foo", recreates it as a
    directory, and receives the file into the new directory.  With
    `--keep-dirlinks`, the receiver keeps the symlink and "file" ends up in
    "bar".

    One note of caution: if you use `--keep-dirlinks`, you must trust all the
    symlinks in the copy! If it is possible for an untrusted user to create
    their own symlink to any directory, the user could then (on a subsequent
    copy) replace the symlink with a real directory and affect the content of
    whatever directory the symlink references.  For backup copies, you are
    better off using something like a bind mount instead of a symlink to modify
    your receiving hierarchy.

    See also `--copy-dirlinks` for an analogous option for the sending side.

0.  `--hard-links`, `-H`

    This tells rsync to look for hard-linked files in the source and link
    together the corresponding files on the destination.  Without this option,
    hard-linked files in the source are treated as though they were separate
    files.

    This option does NOT necessarily ensure that the pattern of hard links on
    the destination exactly matches that on the source.  Cases in which the
    destination may end up with extra hard links include the following:

    - If the destination contains extraneous hard-links (more linking than what
      is present in the source file list), the copying algorithm will not break
      them explicitly.  However, if one or more of the paths have content
      differences, the normal file-update process will break those extra links
      (unless you are using the `--inplace` option).
    - If you specify a `--link-dest` directory that contains hard links, the
      linking of the destination files against the `--link-dest` files can
      cause some paths in the destination to become linked together due to the
      `--link-dest` associations.

    Note that rsync can only detect hard links between files that are inside
    the transfer set.  If rsync updates a file that has extra hard-link
    connections to files outside the transfer, that linkage will be broken.  If
    you are tempted to use the `--inplace` option to avoid this breakage, be
    very careful that you know how your files are being updated so that you are
    certain that no unintended changes happen due to lingering hard links (and
    see the `--inplace` option for more caveats).

    If incremental recursion is active (see `--recursive`), rsync may transfer
    a missing hard-linked file before it finds that another link for that
    contents exists elsewhere in the hierarchy.  This does not affect the
    accuracy of the transfer (i.e. which files are hard-linked together), just
    its efficiency (i.e. copying the data for a new, early copy of a
    hard-linked file that could have been found later in the transfer in
    another member of the hard-linked set of files).  One way to avoid this
    inefficiency is to disable incremental recursion using the
    `--no-inc-recursive` option.

0.  `--perms`, `-p`

    This option causes the receiving rsync to set the destination permissions
    to be the same as the source permissions. (See also the `--chmod` option
    for a way to modify what rsync considers to be the source permissions.)

    When this option is _off_, permissions are set as follows:

    - Existing files (including updated files) retain their existing
      permissions, though the `--executability` option might change just the
      execute permission for the file.
    - New files get their "normal" permission bits set to the source file's
      permissions masked with the receiving directory's default permissions
      (either the receiving process's umask, or the permissions specified via
      the destination directory's default ACL), and their special permission
      bits disabled except in the case where a new directory inherits a setgid
      bit from its parent directory.

    Thus, when `--perms` and `--executability` are both disabled, rsync's
    behavior is the same as that of other file-copy utilities, such as **cp**(1)
    and **tar**(1).

    In summary: to give destination files (both old and new) the source
    permissions, use `--perms`.  To give new files the destination-default
    permissions (while leaving existing files unchanged), make sure that the
    `--perms` option is off and use `--chmod=ugo=rwX` (which ensures that all
    non-masked bits get enabled).  If you'd care to make this latter behavior
    easier to type, you could define a popt alias for it, such as putting this
    line in the file `~/.popt` (the following defines the `-Z` option, and
    includes `--no-g` to use the default group of the destination dir):

    >      rsync alias -Z --no-p --no-g --chmod=ugo=rwX

    You could then use this new option in a command such as this one:

    >      rsync -avZ src/ dest/

    (Caveat: make sure that `-a` does not follow `-Z`, or it will re-enable the
    two `--no-*` options mentioned above.)

    The preservation of the destination's setgid bit on newly-created
    directories when `--perms` is off was added in rsync 2.6.7.  Older rsync
    versions erroneously preserved the three special permission bits for
    newly-created files when `--perms` was off, while overriding the
    destination's setgid bit setting on a newly-created directory.  Default ACL
    observance was added to the ACL patch for rsync 2.6.7, so older (or
    non-ACL-enabled) rsyncs use the umask even if default ACLs are present.
    (Keep in mind that it is the version of the receiving rsync that affects
    these behaviors.)

0.  `--executability`, `-E`

    This option causes rsync to preserve the executability (or
    non-executability) of regular files when `--perms` is not enabled.  A
    regular file is considered to be executable if at least one 'x' is turned
    on in its permissions.  When an existing destination file's executability
    differs from that of the corresponding source file, rsync modifies the
    destination file's permissions as follows:

    - To make a file non-executable, rsync turns off all its 'x' permissions.
    - To make a file executable, rsync turns on each 'x' permission that has a
      corresponding 'r' permission enabled.

    If `--perms` is enabled, this option is ignored.

0.  `--acls`, `-A`

    This option causes rsync to update the destination ACLs to be the same as
    the source ACLs.  The option also implies `--perms`.

    The source and destination systems must have compatible ACL entries for
    this option to work properly.  See the `--fake-super` option for a way to
    backup and restore ACLs that are not compatible.

0.  `--xattrs`, `-X`

    This option causes rsync to update the destination extended attributes to
    be the same as the source ones.

    For systems that support extended-attribute namespaces, a copy being done
    by a super-user copies all namespaces except system.\*.  A normal user only
    copies the user.\* namespace.  To be able to backup and restore non-user
    namespaces as a normal user, see the `--fake-super` option.

    The above name filtering can be overridden by using one or more filter
    options with the **x** modifier.  When you specify an xattr-affecting
    filter rule, rsync requires that you do your own system/user filtering, as
    well as any additional filtering for what xattr names are copied and what
    names are allowed to be deleted.  For example, to skip the system
    namespace, you could specify:

    >     --filter='-x system.*'

    To skip all namespaces except the user namespace, you could specify a
    negated-user match:

    >     --filter='-x! user.*'

    To prevent any attributes from being deleted, you could specify a
    receiver-only rule that excludes all names:

    >     --filter='-xr *'

    Note that the `-X` option does not copy rsync's special xattr values (e.g.
    those used by `--fake-super`) unless you repeat the option (e.g. `-XX`).
    This "copy all xattrs" mode cannot be used with `--fake-super`.

0.  `--chmod=CHMOD`

    This option tells rsync to apply one or more comma-separated "chmod" modes
    to the permission of the files in the transfer.  The resulting value is
    treated as though it were the permissions that the sending side supplied
    for the file, which means that this option can seem to have no effect on
    existing files if `--perms` is not enabled.

    In addition to the normal parsing rules specified in the **chmod**(1)
    manpage, you can specify an item that should only apply to a directory by
    prefixing it with a 'D', or specify an item that should only apply to a
    file by prefixing it with a 'F'.  For example, the following will ensure
    that all directories get marked set-gid, that no files are other-writable,
    that both are user-writable and group-writable, and that both have
    consistent executability across all bits:

    >     --chmod=Dg+s,ug+w,Fo-w,+X

    Using octal mode numbers is also allowed:

    >     --chmod=D2775,F664

    It is also legal to specify multiple `--chmod` options, as each additional
    option is just appended to the list of changes to make.

    See the `--perms` and `--executability` options for how the resulting
    permission value can be applied to the files in the transfer.

0.  `--owner`, `-o`

    This option causes rsync to set the owner of the destination file to be the
    same as the source file, but only if the receiving rsync is being run as
    the super-user (see also the `--super` and `--fake-super` options).  Without
    this option, the owner of new and/or transferred files are set to the
    invoking user on the receiving side.

    The preservation of ownership will associate matching names by default, but
    may fall back to using the ID number in some circumstances (see also the
    `--numeric-ids` option for a full discussion).

0.  `--group`, `-g`

    This option causes rsync to set the group of the destination file to be the
    same as the source file.  If the receiving program is not running as the
    super-user (or if `--no-super` was specified), only groups that the
    invoking user on the receiving side is a member of will be preserved.
    Without this option, the group is set to the default group of the invoking
    user on the receiving side.

    The preservation of group information will associate matching names by
    default, but may fall back to using the ID number in some circumstances
    (see also the `--numeric-ids` option for a full discussion).

0.  `--devices`

    This option causes rsync to transfer character and block device files to
    the remote system to recreate these devices.  This option has no effect if
    the receiving rsync is not run as the super-user (see also the `--super`
    and `--fake-super` options).

0.  `--specials`

    This option causes rsync to transfer special files such as named sockets
    and fifos.

0.  `-D`

    The `-D` option is equivalent to `--devices --specials`.

0.  `--write-devices`

    This tells rsync to treat a device on the receiving side as a regular file,
    allowing the writing of file data into a device.

    This option implies the `--inplace` option.

    Be careful using this, as you should know what devices are present on the
    receiving side of the transfer, especially if running rsync as root.

    This option is refused by an rsync daemon.

0.  `--times`, `-t`

    This tells rsync to transfer modification times along with the files and
    update them on the remote system.  Note that if this option is not used,
    the optimization that excludes files that have not been modified cannot be
    effective; in other words, a missing `-t` or `-a` will cause the next
    transfer to behave as if it used `-I`, causing all files to be updated
    (though rsync's delta-transfer algorithm will make the update fairly
    efficient if the files haven't actually changed, you're much better off
    using `-t`).

0.  `--atimes`, `-U`

    This tells rsync to set the access (use) times of the destination files to
    the same value as the source files.

    If repeated, it also sets the `--open-noatime` option, which can help you
    to make the sending and receiving systems have the same access times on the
    transferred files without needing to run rsync an extra time after a file
    is transferred.

    Note that some older rsync versions (prior to 3.2.0) may have been built
    with a pre-release `--atimes` patch that does not imply `--open-noatime`
    when this option is repeated.

0.  `--open-noatime`

    This tells rsync to open files with the O_NOATIME flag (on systems that
    support it) to avoid changing the access time of the files that are being
    transferred.  If your OS does not support the O_NOATIME flag then rsync
    will silently ignore this option.  Note also that some filesystems are
    mounted to avoid updating the atime on read access even without the
    O_NOATIME flag being set.

0.  `--omit-dir-times`, `-O`

    This tells rsync to omit directories when it is preserving modification
    times (see `--times`).  If NFS is sharing the directories on the receiving
    side, it is a good idea to use `-O`.  This option is inferred if you use
    `--backup` without `--backup-dir`.

    This option also has the side-effect of avoiding early creation of
    directories in incremental recursion copies.  The default `--inc-recursive`
    copying normally does an early-create pass of all the sub-directories in a
    parent directory in order for it to be able to then set the modify time of
    the parent directory right away (without having to delay that until a bunch
    of recursive copying has finished).  This early-create idiom is not
    necessary if directory modify times are not being preserved, so it is
    skipped.  Since early-create directories don't have accurate mode, mtime,
    or ownership, the use of this option can help when someone wants to avoid
    these partially-finished directories.

0.  `--omit-link-times`, `-J`

    This tells rsync to omit symlinks when it is preserving modification times
    (see `--times`).

0.  `--super`

    This tells the receiving side to attempt super-user activities even if the
    receiving rsync wasn't run by the super-user.  These activities include:
    preserving users via the `--owner` option, preserving all groups (not just
    the current user's groups) via the `--groups` option, and copying devices
    via the `--devices` option.  This is useful for systems that allow such
    activities without being the super-user, and also for ensuring that you
    will get errors if the receiving side isn't being run as the super-user.
    To turn off super-user activities, the super-user can use `--no-super`.

0.  `--fake-super`

    When this option is enabled, rsync simulates super-user activities by
    saving/restoring the privileged attributes via special extended attributes
    that are attached to each file (as needed).  This includes the file's owner
    and group (if it is not the default), the file's device info (device &
    special files are created as empty text files), and any permission bits
    that we won't allow to be set on the real file (e.g. the real file gets
    u-s,g-s,o-t for safety) or that would limit the owner's access (since the
    real super-user can always access/change a file, the files we create can
    always be accessed/changed by the creating user).  This option also handles
    ACLs (if `--acls` was specified) and non-user extended attributes (if
    `--xattrs` was specified).

    This is a good way to backup data without using a super-user, and to store
    ACLs from incompatible systems.

    The `--fake-super` option only affects the side where the option is used.
    To affect the remote side of a remote-shell connection, use the
    `--remote-option` (`-M`) option:

    >     rsync -av -M--fake-super /src/ host:/dest/

    For a local copy, this option affects both the source and the destination.
    If you wish a local copy to enable this option just for the destination
    files, specify `-M--fake-super`.  If you wish a local copy to enable this
    option just for the source files, combine `--fake-super` with `-M--super`.

    This option is overridden by both `--super` and `--no-super`.

    See also the "`fake super`" setting in the daemon's rsyncd.conf file.

0.  `--sparse`, `-S`

    Try to handle sparse files efficiently so they take up less space on the
    destination.  If combined with `--inplace` the file created might not end
    up with sparse blocks with some combinations of kernel version and/or
    filesystem type.  If `--whole-file` is in effect (e.g. for a local copy)
    then it will always work because rsync truncates the file prior to writing
    out the updated version.

    Note that versions of rsync older than 3.1.3 will reject the combination of
    `--sparse` and `--inplace`.

0.  `--preallocate`

    This tells the receiver to allocate each destination file to its eventual
    size before writing data to the file.  Rsync will only use the real
    filesystem-level preallocation support provided by Linux's **fallocate**(2)
    system call or Cygwin's **posix_fallocate**(3), not the slow glibc
    implementation that writes a null byte into each block.

    Without this option, larger files may not be entirely contiguous on the
    filesystem, but with this option rsync will probably copy more slowly.  If
    the destination is not an extent-supporting filesystem (such as ext4, xfs,
    NTFS, etc.), this option may have no positive effect at all.

    If combined with `--sparse`, the file will only have sparse blocks (as
    opposed to allocated sequences of null bytes) if the kernel version and
    filesystem type support creating holes in the allocated data.

0.  `--dry-run`, `-n`

    This makes rsync perform a trial run that doesn't make any changes (and
    produces mostly the same output as a real run).  It is most commonly used
    in combination with the `--verbose`, `-v` and/or `--itemize-changes`, `-i`
    options to see what an rsync command is going to do before one actually
    runs it.

    The output of `--itemize-changes` is supposed to be exactly the same on a
    dry run and a subsequent real run (barring intentional trickery and system
    call failures); if it isn't, that's a bug.  Other output should be mostly
    unchanged, but may differ in some areas.  Notably, a dry run does not send
    the actual data for file transfers, so `--progress` has no effect, the
    "bytes sent", "bytes received", "literal data", and "matched data"
    statistics are too small, and the "speedup" value is equivalent to a run
    where no file transfers were needed.

0.  `--whole-file`, `-W`

    This option disables rsync's delta-transfer algorithm, which causes all
    transferred files to be sent whole.  The transfer may be faster if this
    option is used when the bandwidth between the source and destination
    machines is higher than the bandwidth to disk (especially when the "disk"
    is actually a networked filesystem).  This is the default when both the
    source and destination are specified as local paths, but only if no
    batch-writing option is in effect.

0.  `--checksum-choice=STR`, `--cc=STR`

    This option overrides the checksum algorithms.  If one algorithm name is
    specified, it is used for both the transfer checksums and (assuming
    `--checksum` is specified) the pre-transfer checksums.  If two
    comma-separated names are supplied, the first name affects the transfer
    checksums, and the second name affects the pre-transfer checksums (`-c`).

    The checksum options that you may be able to use are:

    - `auto` (the default automatic choice)
    - `xxh128`
    - `xxh3`
    - `xxh64` (aka `xxhash`)
    - `md5`
    - `md4`
    - `none`

    Run `rsync -V` to see the default checksum list compiled into your version
    (which may differ from the above list).

    If "none" is specified for the first (or only) name, the `--whole-file`
    option is forced on and no checksum verification is performed on the
    transferred data.  If "none" is specified for the second (or only) name,
    the `--checksum` option cannot be used.

    The "auto" option is the default, where rsync bases its algorithm choice on
    a negotiation between the client and the server as follows:

    When both sides of the transfer are at least 3.2.0, rsync chooses the first
    algorithm in the client's list of choices that is also in the server's list
    of choices.  If no common checksum choice is found, rsync exits with
    an error.  If the remote rsync is too old to support checksum negotiation,
    a value is chosen based on the protocol version (which chooses between MD5
    and various flavors of MD4 based on protocol age).

    The default order can be customized by setting the environment variable
    RSYNC_CHECKSUM_LIST to a space-separated list of acceptable checksum names.
    If the environment variable contains a "`&`" character, the string is
    separated into the "client list & server list" otherwise the same string
    applies to both.  If the string (or string portion) contains no
    non-whitespace characters, the default checksum list is used.  This method
    does not allow you to specify the transfer checksum separately from the
    pre-transfer checksum, and it discards "auto" and all unknown checksum
    names.  A list with only invalid names results in a failed negotiation.

    The use of the `--checksum-choice` option overrides this environment list.

0.  `--one-file-system`, `-x`

    This tells rsync to avoid crossing a filesystem boundary when recursing.
    This does not limit the user's ability to specify items to copy from
    multiple filesystems, just rsync's recursion through the hierarchy of each
    directory that the user specified, and also the analogous recursion on the
    receiving side during deletion.  Also keep in mind that rsync treats a
    "bind" mount to the same device as being on the same filesystem.

    If this option is repeated, rsync omits all mount-point directories from
    the copy.  Otherwise, it includes an empty directory at each mount-point it
    encounters (using the attributes of the mounted directory because those of
    the underlying mount-point directory are inaccessible).

    If rsync has been told to collapse symlinks (via `--copy-links` or
    `--copy-unsafe-links`), a symlink to a directory on another device is
    treated like a mount-point.  Symlinks to non-directories are unaffected by
    this option.

0.  `--existing`, `--ignore-non-existing`

    This tells rsync to skip creating files (including directories) that do not
    exist yet on the destination.  If this option is combined with the
    `--ignore-existing` option, no files will be updated (which can be useful
    if all you want to do is delete extraneous files).

    This option is a transfer rule, not an exclude, so it doesn't affect the
    data that goes into the file-lists, and thus it doesn't affect deletions.
    It just limits the files that the receiver requests to be transferred.

0.  `--ignore-existing`

    This tells rsync to skip updating files that already exist on the
    destination (this does _not_ ignore existing directories, or nothing would
    get done).  See also `--existing`.

    This option is a transfer rule, not an exclude, so it doesn't affect the
    data that goes into the file-lists, and thus it doesn't affect deletions.
    It just limits the files that the receiver requests to be transferred.

    This option can be useful for those doing backups using the `--link-dest`
    option when they need to continue a backup run that got interrupted.  Since
    a `--link-dest` run is copied into a new directory hierarchy (when it is
    used properly), using `--ignore-existing` will ensure that the
    already-handled files don't get tweaked (which avoids a change in
    permissions on the hard-linked files).  This does mean that this option is
    only looking at the existing files in the destination hierarchy itself.

0.  `--remove-source-files`

    This tells rsync to remove from the sending side the files (meaning
    non-directories) that are a part of the transfer and have been successfully
    duplicated on the receiving side.

    Note that you should only use this option on source files that are
    quiescent.  If you are using this to move files that show up in a
    particular directory over to another host, make sure that the finished
    files get renamed into the source directory, not directly written into it,
    so that rsync can't possibly transfer a file that is not yet fully written.
    If you can't first write the files into a different directory, you should
    use a naming idiom that lets rsync avoid transferring files that are not
    yet finished (e.g. name the file "foo.new" when it is written, rename it to
    "foo" when it is done, and then use the option `--exclude='*.new'` for the
    rsync transfer).

    Starting with 3.1.0, rsync will skip the sender-side removal (and output an
    error) if the file's size or modify time has not stayed unchanged.

0.  `--delete`

    This tells rsync to delete extraneous files from the receiving side (ones
    that aren't on the sending side), but only for the directories that are
    being synchronized.  You must have asked rsync to send the whole directory
    (e.g. "`dir`" or "`dir/`") without using a wildcard for the directory's
    contents (e.g. "`dir/*`") since the wildcard is expanded by the shell and
    rsync thus gets a request to transfer individual files, not the files'
    parent directory.  Files that are excluded from the transfer are also
    excluded from being deleted unless you use the `--delete-excluded` option
    or mark the rules as only matching on the sending side (see the
    include/exclude modifiers in the FILTER RULES section).

    Prior to rsync 2.6.7, this option would have no effect unless `--recursive`
    was enabled.  Beginning with 2.6.7, deletions will also occur when `--dirs`
    (`-d`) is enabled, but only for directories whose contents are being
    copied.

    This option can be dangerous if used incorrectly! It is a very good idea to
    first try a run using the `--dry-run` option (`-n`) to see what files are
    going to be deleted.

    If the sending side detects any I/O errors, then the deletion of any files
    at the destination will be automatically disabled.  This is to prevent
    temporary filesystem failures (such as NFS errors) on the sending side from
    causing a massive deletion of files on the destination.  You can override
    this with the `--ignore-errors` option.

    The `--delete` option may be combined with one of the --delete-WHEN options
    without conflict, as well as `--delete-excluded`.  However, if none of the
    `--delete-WHEN` options are specified, rsync will choose the
    `--delete-during` algorithm when talking to rsync 3.0.0 or newer, and the
    `--delete-before` algorithm when talking to an older rsync.  See also
    `--delete-delay` and `--delete-after`.

0.  `--delete-before`

    Request that the file-deletions on the receiving side be done before the
    transfer starts.  See `--delete` (which is implied) for more details on
    file-deletion.

    Deleting before the transfer is helpful if the filesystem is tight for
    space and removing extraneous files would help to make the transfer
    possible.  However, it does introduce a delay before the start of the
    transfer, and this delay might cause the transfer to timeout (if
    `--timeout` was specified).  It also forces rsync to use the old,
    non-incremental recursion algorithm that requires rsync to scan all the
    files in the transfer into memory at once (see `--recursive`).

0.  `--delete-during`, `--del`

    Request that the file-deletions on the receiving side be done incrementally
    as the transfer happens.  The per-directory delete scan is done right
    before each directory is checked for updates, so it behaves like a more
    efficient `--delete-before`, including doing the deletions prior to any
    per-directory filter files being updated.  This option was first added in
    rsync version 2.6.4.  See `--delete` (which is implied) for more details on
    file-deletion.

0.  `--delete-delay`

    Request that the file-deletions on the receiving side be computed during
    the transfer (like `--delete-during`), and then removed after the transfer
    completes.  This is useful when combined with `--delay-updates` and/or
    `--fuzzy`, and is more efficient than using `--delete-after` (but can
    behave differently, since `--delete-after` computes the deletions in a
    separate pass after all updates are done).  If the number of removed files
    overflows an internal buffer, a temporary file will be created on the
    receiving side to hold the names (it is removed while open, so you
    shouldn't see it during the transfer).  If the creation of the temporary
    file fails, rsync will try to fall back to using `--delete-after` (which it
    cannot do if `--recursive` is doing an incremental scan).  See `--delete`
    (which is implied) for more details on file-deletion.

0.  `--delete-after`

    Request that the file-deletions on the receiving side be done after the
    transfer has completed.  This is useful if you are sending new
    per-directory merge files as a part of the transfer and you want their
    exclusions to take effect for the delete phase of the current transfer.  It
    also forces rsync to use the old, non-incremental recursion algorithm that
    requires rsync to scan all the files in the transfer into memory at once
    (see `--recursive`). See `--delete` (which is implied) for more details on
    file-deletion.

0.  `--delete-excluded`

    In addition to deleting the files on the receiving side that are not on the
    sending side, this tells rsync to also delete any files on the receiving
    side that are excluded (see `--exclude`).  See the FILTER RULES section for
    a way to make individual exclusions behave this way on the receiver, and
    for a way to protect files from `--delete-excluded`.  See `--delete` (which
    is implied) for more details on file-deletion.

0.  `--ignore-missing-args`

    When rsync is first processing the explicitly requested source files (e.g.
    command-line arguments or `--files-from` entries), it is normally an error
    if the file cannot be found.  This option suppresses that error, and does
    not try to transfer the file.  This does not affect subsequent
    vanished-file errors if a file was initially found to be present and later
    is no longer there.

0.  `--delete-missing-args`

    This option takes the behavior of (the implied) `--ignore-missing-args`
    option a step farther: each missing arg will become a deletion request of
    the corresponding destination file on the receiving side (should it exist).
    If the destination file is a non-empty directory, it will only be
    successfully deleted if `--force` or `--delete` are in effect.  Other than
    that, this option is independent of any other type of delete processing.

    The missing source files are represented by special file-list entries which
    display as a "`*missing`" entry in the `--list-only` output.

0.  `--ignore-errors`

    Tells `--delete` to go ahead and delete files even when there are I/O
    errors.

0.  `--force`

    This option tells rsync to delete a non-empty directory when it is to be
    replaced by a non-directory.  This is only relevant if deletions are not
    active (see `--delete` for details).

    Note for older rsync versions: `--force` used to still be required when
    using `--delete-after`, and it used to be non-functional unless the
    `--recursive` option was also enabled.

0.  `--max-delete=NUM`

    This tells rsync not to delete more than NUM files or directories.  If that
    limit is exceeded, all further deletions are skipped through the end of the
    transfer.  At the end, rsync outputs a warning (including a count of the
    skipped deletions) and exits with an error code of 25 (unless some more
    important error condition also occurred).

    Beginning with version 3.0.0, you may specify `--max-delete=0` to be warned
    about any extraneous files in the destination without removing any of them.
    Older clients interpreted this as "unlimited", so if you don't know what
    version the client is, you can use the less obvious `--max-delete=-1` as a
    backward-compatible way to specify that no deletions be allowed (though
    really old versions didn't warn when the limit was exceeded).

0.  `--max-size=SIZE`

    This tells rsync to avoid transferring any file that is larger than the
    specified SIZE.  The SIZE value can be suffixed with a string to indicate a
    size multiplier, and may be a fractional value (e.g. `--max-size=1.5m`).

    This option is a transfer rule, not an exclude, so it doesn't affect the
    data that goes into the file-lists, and thus it doesn't affect deletions.
    It just limits the files that the receiver requests to be transferred.

    The accepted suffix letters are: `B`, `K`, `G`, `T`, and `P` for bytes,
    kilobytes/kibibytes, megabytes/mebibytes, gigabytes/gibibytes,
    terabytes/tebibytes, and petabytes/pebibytes.  If you use a single-char
    suffix or add-on "ib" to it (e.g. "G" or "GiB") then you get units that are
    multiples of 1024.  If you use a two-letter suffix that ends with a "B"
    (e.g. "kb") then you get units that are multiples of 1000.  The suffix
    letters can be any mix of upper and lower-case that you want to use.

    Finally, if the string ends with either "+1" or "-1", it is offset by one
    byte in the indicated direction.  The largest possible value is `8192P-1`.

    Examples: `--max-size=1.5mb-1` is 1499999 bytes, and `--max-size=2g+1` is
    2147483649 bytes.

    Note that rsync versions prior to 3.1.0 did not allow `--max-size=0`.

0.  `--min-size=SIZE`

    This tells rsync to avoid transferring any file that is smaller than the
    specified SIZE, which can help in not transferring small, junk files.  See
    the `--max-size` option for a description of SIZE and other information.

    Note that rsync versions prior to 3.1.0 did not allow `--min-size=0`.

0.  `--max-alloc=SIZE`

    By default rsync limits an individual malloc/realloc to about 1GB in size.
    For most people this limit works just fine and prevents a protocol error
    causing rsync to request massive amounts of memory.  However, if you have
    many millions of files in a transfer, a large amount of server memory, and
    you don't want to split up your transfer into multiple parts, you can
    increase the per-allocation limit to something larger and rsync will
    consume more memory.

    Keep in mind that this is not a limit on the total size of allocated
    memory.  It is a sanity-check value for each individual allocation.

    See the `--max-size` option for a description of how SIZE can be specified.
    The default suffix if none is given is bytes.

    You can set a default value using the environment variable RSYNC_MAX_ALLOC
    using the same SIZE values as supported by this option.  If the remote
    rsync doesn't understand the `--max-alloc` option, you can override an
    environmental value by specifying `--max-alloc=1g`, which will make rsync
    avoid sending the option to the remote side (because "1G" is the default).

0.  `--block-size=SIZE`, `-B`

    This forces the block size used in rsync's delta-transfer algorithm to a
    fixed value.  It is normally selected based on the size of each file being
    updated.  See the technical report for details.

0.  `--rsh=COMMAND`, `-e`

    This option allows you to choose an alternative remote shell program to use
    for communication between the local and remote copies of rsync.  Typically,
    rsync is configured to use ssh by default, but you may prefer to use rsh on
    a local network.

    If this option is used with `[user@]host::module/path`, then the remote
    shell _COMMAND_ will be used to run an rsync daemon on the remote host, and
    all data will be transmitted through that remote shell connection, rather
    than through a direct socket connection to a running rsync daemon on the
    remote host.  See the section "USING RSYNC-DAEMON FEATURES VIA A
    REMOTE-SHELL CONNECTION" above.

    Beginning with rsync 3.2.0, the RSYNC_PORT environment variable will be set
    when a daemon connection is being made via a remote-shell connection.  It
    is set to 0 if the default daemon port is being assumed, or it is set to
    the value of the rsync port that was specified via either the `--port`
    option or a non-empty port value in an rsync:// URL.  This allows the
    script to discern if a non-default port is being requested, allowing for
    things such as an SSL or stunnel helper script to connect to a default or
    alternate port.

    Command-line arguments are permitted in COMMAND provided that COMMAND is
    presented to rsync as a single argument.  You must use spaces (not tabs or
    other whitespace) to separate the command and args from each other, and you
    can use single- and/or double-quotes to preserve spaces in an argument (but
    not backslashes).  Note that doubling a single-quote inside a single-quoted
    string gives you a single-quote; likewise for double-quotes (though you
    need to pay attention to which quotes your shell is parsing and which
    quotes rsync is parsing).  Some examples:

    >     -e 'ssh -p 2234'
    >     -e 'ssh -o "ProxyCommand nohup ssh firewall nc -w1 %h %p"'

    (Note that ssh users can alternately customize site-specific connect
    options in their .ssh/config file.)

    You can also choose the remote shell program using the RSYNC_RSH
    environment variable, which accepts the same range of values as `-e`.

    See also the `--blocking-io` option which is affected by this option.

0.  `--rsync-path=PROGRAM`

    Use this to specify what program is to be run on the remote machine to
    start-up rsync.  Often used when rsync is not in the default remote-shell's
    path (e.g. `--rsync-path=/usr/local/bin/rsync`).  Note that PROGRAM is run
    with the help of a shell, so it can be any program, script, or command
    sequence you'd care to run, so long as it does not corrupt the standard-in
    & standard-out that rsync is using to communicate.

    One tricky example is to set a different default directory on the remote
    machine for use with the `--relative` option.  For instance:

    >     rsync -avR --rsync-path="cd /a/b && rsync" host:c/d /e/

0.  `--remote-option=OPTION`, `-M`

    This option is used for more advanced situations where you want certain
    effects to be limited to one side of the transfer only.  For instance, if
    you want to pass `--log-file=FILE` and `--fake-super` to the remote system,
    specify it like this:

    >     rsync -av -M --log-file=foo -M--fake-super src/ dest/

    If you want to have an option affect only the local side of a transfer when
    it normally affects both sides, send its negation to the remote side.  Like
    this:

    >     rsync -av -x -M--no-x src/ dest/

    Be cautious using this, as it is possible to toggle an option that will
    cause rsync to have a different idea about what data to expect next over
    the socket, and that will make it fail in a cryptic fashion.

    Note that it is best to use a separate `--remote-option` for each option
    you want to pass.  This makes your usage compatible with the
    `--protect-args` option.  If that option is off, any spaces in your remote
    options will be split by the remote shell unless you take steps to protect
    them.

    When performing a local transfer, the "local" side is the sender and the
    "remote" side is the receiver.

    Note some versions of the popt option-parsing library have a bug in them
    that prevents you from using an adjacent arg with an equal in it next to a
    short option letter (e.g. `-M--log-file=/tmp/foo`).  If this bug affects
    your version of popt, you can use the version of popt that is included with
    rsync.

0.  `--cvs-exclude`, `-C`

    This is a useful shorthand for excluding a broad range of files that you
    often don't want to transfer between systems.  It uses a similar algorithm
    to CVS to determine if a file should be ignored.

    The exclude list is initialized to exclude the following items (these
    initial items are marked as perishable -- see the FILTER RULES section):

    [comment]: # (This list gets used for the default-cvsignore.h file.)

    > `RCS`
    > `SCCS`
    > `CVS`
    > `CVS.adm`
    > `RCSLOG`
    > `cvslog.*`
    > `tags`
    > `TAGS`
    > `.make.state`
    > `.nse_depinfo`
    > `*~`
    > `#*`
    > `.#*`
    > `,*`
    > `_$*`
    > `*$`
    > `*.old`
    > `*.bak`
    > `*.BAK`
    > `*.orig`
    > `*.rej`
    > `.del-*`
    > `*.a`
    > `*.olb`
    > `*.o`
    > `*.obj`
    > `*.so`
    > `*.exe`
    > `*.Z`
    > `*.elc`
    > `*.ln`
    > `core`
    > `.svn/`
    > `.git/`
    > `.hg/`
    > `.bzr/`

    then, files listed in a $HOME/.cvsignore are added to the list and any
    files listed in the CVSIGNORE environment variable (all cvsignore names are
    delimited by whitespace).

    Finally, any file is ignored if it is in the same directory as a .cvsignore
    file and matches one of the patterns listed therein.  Unlike rsync's
    filter/exclude files, these patterns are split on whitespace.  See the
    **cvs**(1) manual for more information.

    If you're combining `-C` with your own `--filter` rules, you should note
    that these CVS excludes are appended at the end of your own rules,
    regardless of where the `-C` was placed on the command-line.  This makes
    them a lower priority than any rules you specified explicitly.  If you want
    to control where these CVS excludes get inserted into your filter rules,
    you should omit the `-C` as a command-line option and use a combination of
    `--filter=:C` and `--filter=-C` (either on your command-line or by putting
    the ":C" and "-C" rules into a filter file with your other rules).  The
    first option turns on the per-directory scanning for the .cvsignore file.
    The second option does a one-time import of the CVS excludes mentioned
    above.

0.  `--filter=RULE`, `-f`

    This option allows you to add rules to selectively exclude certain files
    from the list of files to be transferred.  This is most useful in
    combination with a recursive transfer.

    You may use as many `--filter` options on the command line as you like to
    build up the list of files to exclude.  If the filter contains whitespace,
    be sure to quote it so that the shell gives the rule to rsync as a single
    argument.  The text below also mentions that you can use an underscore to
    replace the space that separates a rule from its arg.

    See the FILTER RULES section for detailed information on this option.

0.  `-F`

    The `-F` option is a shorthand for adding two `--filter` rules to your
    command.  The first time it is used is a shorthand for this rule:

    >     --filter='dir-merge /.rsync-filter'

    This tells rsync to look for per-directory .rsync-filter files that have
    been sprinkled through the hierarchy and use their rules to filter the
    files in the transfer.  If `-F` is repeated, it is a shorthand for this
    rule:

    >     --filter='exclude .rsync-filter'

    This filters out the .rsync-filter files themselves from the transfer.

    See the FILTER RULES section for detailed information on how these options
    work.

0.  `--exclude=PATTERN`

    This option is a simplified form of the `--filter` option that defaults to
    an exclude rule and does not allow the full rule-parsing syntax of normal
    filter rules.

    See the FILTER RULES section for detailed information on this option.

0.  `--exclude-from=FILE`

    This option is related to the `--exclude` option, but it specifies a FILE
    that contains exclude patterns (one per line).  Blank lines in the file and
    lines starting with '`;`' or '`#`' are ignored.  If _FILE_ is '`-`', the
    list will be read from standard input.

0.  `--include=PATTERN`

    This option is a simplified form of the `--filter` option that defaults to
    an include rule and does not allow the full rule-parsing syntax of normal
    filter rules.

    See the FILTER RULES section for detailed information on this option.

0.  `--include-from=FILE`

    This option is related to the `--include` option, but it specifies a FILE
    that contains include patterns (one per line).  Blank lines in the file and
    lines starting with '`;`' or '`#`' are ignored.  If _FILE_ is '`-`', the
    list will be read from standard input.

0.  `--files-from=FILE`

    Using this option allows you to specify the exact list of files to transfer
    (as read from the specified FILE or '`-`' for standard input).  It also
    tweaks the default behavior of rsync to make transferring just the
    specified files and directories easier:

    - The `--relative` (`-R`) option is implied, which preserves the path
      information that is specified for each item in the file (use
      `--no-relative` or `--no-R` if you want to turn that off).
    - The `--dirs` (`-d`) option is implied, which will create directories
      specified in the list on the destination rather than noisily skipping
      them (use `--no-dirs` or `--no-d` if you want to turn that off).
    - The `--archive` (`-a`) option's behavior does not imply `--recursive`
      (`-r`), so specify it explicitly, if you want it.
    - These side-effects change the default state of rsync, so the position of
      the `--files-from` option on the command-line has no bearing on how other
      options are parsed (e.g. `-a` works the same before or after
      `--files-from`, as does `--no-R` and all other options).

    The filenames that are read from the FILE are all relative to the source
    dir -- any leading slashes are removed and no ".." references are allowed
    to go higher than the source dir.  For example, take this command:

    >     rsync -a --files-from=/tmp/foo /usr remote:/backup

    If /tmp/foo contains the string "bin" (or even "/bin"), the /usr/bin
    directory will be created as /backup/bin on the remote host.  If it
    contains "bin/" (note the trailing slash), the immediate contents of the
    directory would also be sent (without needing to be explicitly mentioned in
    the file -- this began in version 2.6.4).  In both cases, if the `-r`
    option was enabled, that dir's entire hierarchy would also be transferred
    (keep in mind that `-r` needs to be specified explicitly with
    `--files-from`, since it is not implied by `-a`).  Also note that the
    effect of the (enabled by default) `--relative` option is to duplicate only
    the path info that is read from the file -- it does not force the
    duplication of the source-spec path (/usr in this case).

    In addition, the `--files-from` file can be read from the remote host
    instead of the local host if you specify a "host:" in front of the file
    (the host must match one end of the transfer).  As a short-cut, you can
    specify just a prefix of ":" to mean "use the remote end of the transfer".
    For example:

    >     rsync -a --files-from=:/path/file-list src:/ /tmp/copy

    This would copy all the files specified in the /path/file-list file that
    was located on the remote "src" host.

    If the `--iconv` and `--protect-args` options are specified and the
    `--files-from` filenames are being sent from one host to another, the
    filenames will be translated from the sending host's charset to the
    receiving host's charset.

    NOTE: sorting the list of files in the `--files-from` input helps rsync to
    be more efficient, as it will avoid re-visiting the path elements that are
    shared between adjacent entries.  If the input is not sorted, some path
    elements (implied directories) may end up being scanned multiple times, and
    rsync will eventually unduplicate them after they get turned into file-list
    elements.

0.  `--from0`, `-0`

    This tells rsync that the rules/filenames it reads from a file are
    terminated by a null ('\\0') character, not a NL, CR, or CR+LF.  This
    affects `--exclude-from`, `--include-from`, `--files-from`, and any merged
    files specified in a `--filter` rule.  It does not affect `--cvs-exclude`
    (since all names read from a .cvsignore file are split on whitespace).

0.  `--protect-args`, `-s`

    This option sends all filenames and most options to the remote rsync
    without allowing the remote shell to interpret them.  This means that
    spaces are not split in names, and any non-wildcard special characters are
    not translated (such as `~`, `$`, `;`, `&`, etc.).  Wildcards are expanded
    on the remote host by rsync (instead of the shell doing it).

    If you use this option with `--iconv`, the args related to the remote side
    will also be translated from the local to the remote character-set.  The
    translation happens before wild-cards are expanded.  See also the
    `--files-from` option.

    You may also control this option via the RSYNC_PROTECT_ARGS environment
    variable.  If this variable has a non-zero value, this option will be
    enabled by default, otherwise it will be disabled by default.  Either state
    is overridden by a manually specified positive or negative version of this
    option (note that `--no-s` and `--no-protect-args` are the negative
    versions).  Since this option was first introduced in 3.0.0, you'll need to
    make sure it's disabled if you ever need to interact with a remote rsync
    that is older than that.

    Rsync can also be configured (at build time) to have this option enabled by
    default (with is overridden by both the environment and the command-line).
    Run `rsync -V` to check if this is the case, as it will display "default
    protect-args" or "optional protect-args" depending on how it was compiled.

    This option will eventually become a new default setting at some
    as-yet-undetermined point in the future.

0.  `--copy-as=USER[:GROUP]`

    This option instructs rsync to use the USER and (if specified after a
    colon) the GROUP for the copy operations.  This only works if the user that
    is running rsync has the ability to change users.  If the group is not
    specified then the user's default groups are used.

    This option can help to reduce the risk of an rsync being run as root into
    or out of a directory that might have live changes happening to it and you
    want to make sure that root-level read or write actions of system files are
    not possible.  While you could alternatively run all of rsync as the
    specified user, sometimes you need the root-level host-access credentials
    to be used, so this allows rsync to drop root for the copying part of the
    operation after the remote-shell or daemon connection is established.

    The option only affects one side of the transfer unless the transfer is
    local, in which case it affects both sides.  Use the `--remote-option` to
    affect the remote side, such as `-M--copy-as=joe`.  For a local transfer,
    the lsh (or lsh.sh) support file provides a local-shell helper script that
    can be used to allow a "localhost:" or "lh:" host-spec to be specified
    without needing to setup any remote shells, allowing you to specify remote
    options that affect the side of the transfer that is using the host-spec
    (and using hostname "lh" avoids the overriding of the remote directory to
    the user's home dir).

    For example, the following rsync writes the local files as user "joe":

    >     sudo rsync -aiv --copy-as=joe host1:backups/joe/ /home/joe/

    This makes all files owned by user "joe", limits the groups to those that
    are available to that user, and makes it impossible for the joe user to do
    a timed exploit of the path to induce a change to a file that the joe user
    has no permissions to change.

    The following command does a local copy into the "dest/" dir as user "joe"
    (assumimg you've installed support/lsh into a dir on your $PATH):

    >     sudo rsync -aive lsh -M--copy-as=joe src/ lh:dest/

0.  `--temp-dir=DIR`, `-T`

    This option instructs rsync to use DIR as a scratch directory when creating
    temporary copies of the files transferred on the receiving side.  The
    default behavior is to create each temporary file in the same directory as
    the associated destination file.  Beginning with rsync 3.1.1, the temp-file
    names inside the specified DIR will not be prefixed with an extra dot
    (though they will still have a random suffix added).

    This option is most often used when the receiving disk partition does not
    have enough free space to hold a copy of the largest file in the transfer.
    In this case (i.e. when the scratch directory is on a different disk
    partition), rsync will not be able to rename each received temporary file
    over the top of the associated destination file, but instead must copy it
    into place.  Rsync does this by copying the file over the top of the
    destination file, which means that the destination file will contain
    truncated data during this copy.  If this were not done this way (even if
    the destination file were first removed, the data locally copied to a
    temporary file in the destination directory, and then renamed into place)
    it would be possible for the old file to continue taking up disk space (if
    someone had it open), and thus there might not be enough room to fit the
    new version on the disk at the same time.

    If you are using this option for reasons other than a shortage of disk
    space, you may wish to combine it with the `--delay-updates` option, which
    will ensure that all copied files get put into subdirectories in the
    destination hierarchy, awaiting the end of the transfer.  If you don't have
    enough room to duplicate all the arriving files on the destination
    partition, another way to tell rsync that you aren't overly concerned about
    disk space is to use the `--partial-dir` option with a relative path;
    because this tells rsync that it is OK to stash off a copy of a single file
    in a subdir in the destination hierarchy, rsync will use the partial-dir as
    a staging area to bring over the copied file, and then rename it into place
    from there. (Specifying a `--partial-dir` with an absolute path does not
    have this side-effect.)

0.  `--fuzzy`, `-y`

    This option tells rsync that it should look for a basis file for any
    destination file that is missing.  The current algorithm looks in the same
    directory as the destination file for either a file that has an identical
    size and modified-time, or a similarly-named file.  If found, rsync uses
    the fuzzy basis file to try to speed up the transfer.

    If the option is repeated, the fuzzy scan will also be done in any matching
    alternate destination directories that are specified via `--compare-dest`,
    `--copy-dest`, or `--link-dest`.

    Note that the use of the `--delete` option might get rid of any potential
    fuzzy-match files, so either use `--delete-after` or specify some filename
    exclusions if you need to prevent this.

0.  `--compare-dest=DIR`

    This option instructs rsync to use _DIR_ on the destination machine as an
    additional hierarchy to compare destination files against doing transfers
    (if the files are missing in the destination directory).  If a file is
    found in _DIR_ that is identical to the sender's file, the file will NOT be
    transferred to the destination directory.  This is useful for creating a
    sparse backup of just files that have changed from an earlier backup.  This
    option is typically used to copy into an empty (or newly created)
    directory.

    Beginning in version 2.6.4, multiple `--compare-dest` directories may be
    provided, which will cause rsync to search the list in the order specified
    for an exact match.  If a match is found that differs only in attributes, a
    local copy is made and the attributes updated.  If a match is not found, a
    basis file from one of the _DIRs_ will be selected to try to speed up the
    transfer.

    If _DIR_ is a relative path, it is relative to the destination directory.
    See also `--copy-dest` and `--link-dest`.

    NOTE: beginning with version 3.1.0, rsync will remove a file from a
    non-empty destination hierarchy if an exact match is found in one of the
    compare-dest hierarchies (making the end result more closely match a fresh
    copy).

0.  `--copy-dest=DIR`

    This option behaves like `--compare-dest`, but rsync will also copy
    unchanged files found in _DIR_ to the destination directory using a local
    copy.  This is useful for doing transfers to a new destination while
    leaving existing files intact, and then doing a flash-cutover when all
    files have been successfully transferred.

    Multiple `--copy-dest` directories may be provided, which will cause rsync
    to search the list in the order specified for an unchanged file.  If a
    match is not found, a basis file from one of the _DIRs_ will be selected to
    try to speed up the transfer.

    If _DIR_ is a relative path, it is relative to the destination directory.
    See also `--compare-dest` and `--link-dest`.

0.  `--link-dest=DIR`

    This option behaves like `--copy-dest`, but unchanged files are hard linked
    from _DIR_ to the destination directory.  The files must be identical in
    all preserved attributes (e.g. permissions, possibly ownership) in order
    for the files to be linked together.  An example:

    >     rsync -av --link-dest=$PWD/prior_dir host:src_dir/ new_dir/

    If file's aren't linking, double-check their attributes.  Also check if
    some attributes are getting forced outside of rsync's control, such a mount
    option that squishes root to a single user, or mounts a removable drive
    with generic ownership (such as OS X's "Ignore ownership on this volume"
    option).

    Beginning in version 2.6.4, multiple `--link-dest` directories may be
    provided, which will cause rsync to search the list in the order specified
    for an exact match (there is a limit of 20 such directories).  If a match
    is found that differs only in attributes, a local copy is made and the
    attributes updated.  If a match is not found, a basis file from one of the
    _DIRs_ will be selected to try to speed up the transfer.

    This option works best when copying into an empty destination hierarchy, as
    existing files may get their attributes tweaked, and that can affect
    alternate destination files via hard-links.  Also, itemizing of changes can
    get a bit muddled.  Note that prior to version 3.1.0, an
    alternate-directory exact match would never be found (nor linked into the
    destination) when a destination file already exists.

    Note that if you combine this option with `--ignore-times`, rsync will not
    link any files together because it only links identical files together as a
    substitute for transferring the file, never as an additional check after
    the file is updated.

    If _DIR_ is a relative path, it is relative to the destination directory.
    See also `--compare-dest` and `--copy-dest`.

    Note that rsync versions prior to 2.6.1 had a bug that could prevent
    `--link-dest` from working properly for a non-super-user when `-o` was
    specified (or implied by `-a`).  You can work-around this bug by avoiding
    the `-o` option when sending to an old rsync.

0.  `--compress`, `-z`

    With this option, rsync compresses the file data as it is sent to the
    destination machine, which reduces the amount of data being transmitted --
    something that is useful over a slow connection.

    Rsync supports multiple compression methods and will choose one for you
    unless you force the choice using the `--compress-choice` option.

    Run `rsync -V` to see the default compress list compiled into your version.

    When both sides of the transfer are at least 3.2.0, rsync chooses the first
    algorithm in the client's list of choices that is also in the server's list
    of choices.  If no common compress choice is found, rsync exits with
    an error.  If the remote rsync is too old to support checksum negotiation,
    its list is assumed to be "zlib".

    The default order can be customized by setting the environment variable
    RSYNC_COMPRESS_LIST to a space-separated list of acceptable compression
    names.  If the environment variable contains a "`&`" character, the string
    is separated into the "client list & server list" otherwise the same string
    applies to both.  If the string (or string portion) contains no
    non-whitespace characters, the default compress list is used.  Any unknown
    compression names are discarded from the list, but a list with only invalid
    names results in a failed negotiation.

    There are some older rsync versions that were configured to reject a `-z`
    option and require the use of `-zz` because their compression library was
    not compatible with the default zlib compression method.  You can usually
    ignore this weirdness unless the rsync server complains and tells you to
    specify `-zz`.

    See also the `--skip-compress` option for the default list of file suffixes
    that will trasnferred with no (or minimal) compression.

0.  `--compress-choice=STR`, `--zc=STR`

    This option can be used to override the automatic negotiation of the
    compression algorithm that occurs when `--compress` is used.  The option
    implies `--compress` unless "none" was specified, which instead implies
    `--no-compress`.

    The compression options that you may be able to use are:

    - `zstd`
    - `lz4`
    - `zlibx`
    - `zlib`
    - `none`

    Run `rsync -V` to see the default compress list compiled into your version
    (which may differ from the above list).

    Note that if you see an error about an option named `--old-compress` or
    `--new-compress`, this is rsync trying to send the `--compress-choice=zlib`
    or `--compress-choice=zlibx` option in a backward-compatible manner that
    more rsync versions understand.  This error indicates that the older rsync
    version on the server will not allow you to force the compression type.

    Note that the "zlibx" compression algorithm is just the "zlib" algorithm
    with matched data excluded from the compression stream (to try to make it
    more compatible with an external zlib implementation).

0.  `--compress-level=NUM`, `--zl=NUM`

    Explicitly set the compression level to use (see `--compress`, `-z`)
    instead of letting it default.  The `--compress` option is implied as long
    as the level chosen is not a "don't compress" level for the compression
    algorithm that is in effect (e.g. zlib compression treats level 0 as
    "off").

    The level values vary depending on the checksum in effect.  Because rsync
    will negotiate a checksum choice by default when the remote rsync is new
    enough, it can be good to combine this option with a `--compress-choice`
    (`--zc`) option unless you're sure of the choice in effect.  For example:

    >     rsync -aiv --zc=zstd --zl=22 host:src/ dest/

    For zlib & zlibx compression the valid values are from 1 to 9 with 6 being
    the default.  Specifying 0 turns compression off, and specifying -1 chooses
    the default of 6.

    For zstd compression the valid values are from -131072 to 22 with 3 being
    the default. Specifying 0 chooses the default of 3.

    For lz4 compression there are no levels, so the value is always 0.

    If you specify a too-large or too-small value, the number is silently
    limited to a valid value.  This allows you to specify something like
    `--zl=999999999` and be assured that you'll end up with the maximum
    compression level no matter what algorithm was chosen.

    If you want to know the compression level that is in effect, specify
    `--debug=nstr` to see the "negotiated string" results.  This will report
    something like "`Client compress: zstd (level 3)`" (along with the checksum
    choice in effect).

0.  `--skip-compress=LIST`

    Override the list of file suffixes that will be compressed as little as
    possible.  Rsync sets the compression level on a per-file basis based on
    the file's suffix.  If the compression algorithm has an "off" level (such
    as zlib/zlibx) then no compression occurs for those files.  Other
    algorithms have the level minimized to reduces the CPU usage as much as
    possible.

    The **LIST** should be one or more file suffixes (without the dot) separated
    by slashes (`/`).  You may specify an empty string to indicate that no files
    should be skipped.

    Simple character-class matching is supported: each must consist of a list
    of letters inside the square brackets (e.g. no special classes, such as
    "[:alpha:]", are supported, and '-' has no special meaning).

    The characters asterisk (`*`) and question-mark (`?`) have no special meaning.

    Here's an example that specifies 6 suffixes to skip (since 1 of the 5 rules
    matches 2 suffixes):

    >     --skip-compress=gz/jpg/mp[34]/7z/bz2

    The default file suffixes in the skip-compress list in this version of
    rsync are:

    [comment]: # (This list gets used for the default-dont-compress.h file.)

    > 7z
    > ace
    > apk
    > avi
    > bz2
    > deb
    > flac
    > gpg
    > gz
    > iso
    > jar
    > jpeg
    > jpg
    > lz
    > lz4
    > lzma
    > lzo
    > mkv
    > mov
    > mp3
    > mp4
    > odb
    > odf
    > odg
    > odi
    > odm
    > odp
    > ods
    > odt
    > ogg
    > ogv
    > opus
    > otg
    > oth
    > otp
    > ots
    > ott
    > oxt
    > png
    > rar
    > rpm
    > rz
    > rzip
    > squashfs
    > sxc
    > sxd
    > sxg
    > sxm
    > sxw
    > tbz
    > tgz
    > tlz
    > txz
    > tzo
    > webm
    > webp
    > xz
    > z
    > zip
    > zst

    This list will be replaced by your `--skip-compress` list in all but one
    situation: a copy from a daemon rsync will add your skipped suffixes to its
    list of non-compressing files (and its list may be configured to a
    different default).

0.  `--numeric-ids`

    With this option rsync will transfer numeric group and user IDs rather than
    using user and group names and mapping them at both ends.

    By default rsync will use the username and groupname to determine what
    ownership to give files.  The special uid 0 and the special group 0 are
    never mapped via user/group names even if the `--numeric-ids` option is not
    specified.

    If a user or group has no name on the source system or it has no match on
    the destination system, then the numeric ID from the source system is used
    instead.  See also the comments on the "`use chroot`" setting in the
    rsyncd.conf manpage for information on how the chroot setting affects
    rsync's ability to look up the names of the users and groups and what you
    can do about it.

0.  `--usermap=STRING`, `--groupmap=STRING`

    These options allow you to specify users and groups that should be mapped
    to other values by the receiving side.  The **STRING** is one or more
    **FROM**:**TO** pairs of values separated by commas.  Any matching **FROM**
    value from the sender is replaced with a **TO** value from the receiver.
    You may specify usernames or user IDs for the **FROM** and **TO** values,
    and the **FROM** value may also be a wild-card string, which will be
    matched against the sender's names (wild-cards do NOT match against ID
    numbers, though see below for why a '`*`' matches everything).  You may
    instead specify a range of ID numbers via an inclusive range: LOW-HIGH.
    For example:

    >     --usermap=0-99:nobody,wayne:admin,*:normal --groupmap=usr:1,1:usr

    The first match in the list is the one that is used.  You should specify
    all your user mappings using a single `--usermap` option, and/or all your
    group mappings using a single `--groupmap` option.

    Note that the sender's name for the 0 user and group are not transmitted to
    the receiver, so you should either match these values using a 0, or use the
    names in effect on the receiving side (typically "root").  All other
    **FROM** names match those in use on the sending side.  All **TO** names
    match those in use on the receiving side.

    Any IDs that do not have a name on the sending side are treated as having
    an empty name for the purpose of matching.  This allows them to be matched
    via a "`*`" or using an empty name.  For instance:

    >     --usermap=:nobody --groupmap=*:nobody

    When the `--numeric-ids` option is used, the sender does not send any
    names, so all the IDs are treated as having an empty name.  This means that
    you will need to specify numeric **FROM** values if you want to map these
    nameless IDs to different values.

    For the `--usermap` option to have any effect, the `-o` (`--owner`) option
    must be used (or implied), and the receiver will need to be running as a
    super-user (see also the `--fake-super` option).  For the `--groupmap`
    option to have any effect, the `-g` (`--groups`) option must be used (or
    implied), and the receiver will need to have permissions to set that group.

0.  `--chown=USER:GROUP`

    This option forces all files to be owned by USER with group GROUP.  This is
    a simpler interface than using `--usermap` and `--groupmap` directly, but
    it is implemented using those options internally, so you cannot mix them.
    If either the USER or GROUP is empty, no mapping for the omitted user/group
    will occur.  If GROUP is empty, the trailing colon may be omitted, but if
    USER is empty, a leading colon must be supplied.

    If you specify "`--chown=foo:bar`", this is exactly the same as specifying
    "`--usermap=*:foo --groupmap=*:bar`", only easier.

0.  `--timeout=SECONDS`

    This option allows you to set a maximum I/O timeout in seconds.  If no data
    is transferred for the specified time then rsync will exit.  The default is
    0, which means no timeout.

0.  `--contimeout=SECONDS`

    This option allows you to set the amount of time that rsync will wait for
    its connection to an rsync daemon to succeed.  If the timeout is reached,
    rsync exits with an error.

0.  `--address=ADDRESS`

    By default rsync will bind to the wildcard address when connecting to an
    rsync daemon.  The `--address` option allows you to specify a specific IP
    address (or hostname) to bind to.  See also this option in the `--daemon`
    mode section.

0.  `--port=PORT`

    This specifies an alternate TCP port number to use rather than the default
    of 873.  This is only needed if you are using the double-colon (::) syntax
    to connect with an rsync daemon (since the URL syntax has a way to specify
    the port as a part of the URL).  See also this option in the `--daemon`
    mode section.

0.  `--sockopts=OPTIONS`

    This option can provide endless fun for people who like to tune their
    systems to the utmost degree.  You can set all sorts of socket options
    which may make transfers faster (or slower!).  Read the man page for the
    `setsockopt()` system call for details on some of the options you may be
    able to set.  By default no special socket options are set.  This only
    affects direct socket connections to a remote rsync daemon.

    This option also exists in the `--daemon` mode section.

0.  `--blocking-io`

    This tells rsync to use blocking I/O when launching a remote shell
    transport.  If the remote shell is either rsh or remsh, rsync defaults to
    using blocking I/O, otherwise it defaults to using non-blocking I/O. (Note
    that ssh prefers non-blocking I/O.)

0.  `--outbuf=MODE`

    This sets the output buffering mode.  The mode can be None (aka
    Unbuffered), Line, or Block (aka Full).  You may specify as little as a
    single letter for the mode, and use upper or lower case.

    The main use of this option is to change Full buffering to Line buffering
    when rsync's output is going to a file or pipe.

0.  `--itemize-changes`, `-i`

    Requests a simple itemized list of the changes that are being made to each
    file, including attribute changes.  This is exactly the same as specifying
    `--out-format='%i %n%L'`.  If you repeat the option, unchanged files will
    also be output, but only if the receiving rsync is at least version 2.6.7
    (you can use `-vv` with older versions of rsync, but that also turns on the
    output of other verbose messages).

    The "%i" escape has a cryptic output that is 11 letters long.  The general
    format is like the string `YXcstpoguax`, where **Y** is replaced by the type
    of update being done, **X** is replaced by the file-type, and the other
    letters represent attributes that may be output if they are being modified.

    The update types that replace the **Y** are as follows:

    - A `<` means that a file is being transferred to the remote host (sent).
    - A `>` means that a file is being transferred to the local host
      (received).
    - A `c` means that a local change/creation is occurring for the item (such
      as the creation of a directory or the changing of a symlink, etc.).
    - A `h` means that the item is a hard link to another item (requires
      `--hard-links`).
    - A `.` means that the item is not being updated (though it might have
      attributes that are being modified).
    - A `*` means that the rest of the itemized-output area contains a message
      (e.g. "deleting").

    The file-types that replace the **X** are: `f` for a file, a `d` for a
    directory, an `L` for a symlink, a `D` for a device, and a `S` for a
    special file (e.g. named sockets and fifos).

    The other letters in the string above are the actual letters that will be
    output if the associated attribute for the item is being updated or a "."
    for no change.  Three exceptions to this are: (1) a newly created item
    replaces each letter with a "+", (2) an identical item replaces the dots
    with spaces, and (3) an unknown attribute replaces each letter with a "?"
    (this can happen when talking to an older rsync).

    The attribute that is associated with each letter is as follows:

    - A `c` means either that a regular file has a different checksum (requires
      `--checksum`) or that a symlink, device, or special file has a changed
      value.  Note that if you are sending files to an rsync prior to 3.0.1,
      this change flag will be present only for checksum-differing regular
      files.
    - A `s` means the size of a regular file is different and will be updated
      by the file transfer.
    - A `t` means the modification time is different and is being updated to
      the sender's value (requires `--times`).  An alternate value of `T` means
      that the modification time will be set to the transfer time, which
      happens when a file/symlink/device is updated without `--times` and when
      a symlink is changed and the receiver can't set its time. (Note: when
      using an rsync 3.0.0 client, you might see the `s` flag combined with `t`
      instead of the proper `T` flag for this time-setting failure.)
    - A `p` means the permissions are different and are being updated to the
      sender's value (requires `--perms`).
    - An `o` means the owner is different and is being updated to the sender's
      value (requires `--owner` and super-user privileges).
    - A `g` means the group is different and is being updated to the sender's
      value (requires `--group` and the authority to set the group).
    - A `u` means the access (use) time is different and is being updated to
      the sender's value (requires `--atimes`).  An alternate value of `U`
      means that the access time will be set to the transfer time, which
      happens when a symlink or directory is updated.
    - The `a` means that the ACL information changed.
    - The `x` means that the extended attribute information changed.

    One other output is possible: when deleting files, the "%i" will output the
    string "`*deleting`" for each item that is being removed (assuming that you
    are talking to a recent enough rsync that it logs deletions instead of
    outputting them as a verbose message).

0.  `--out-format=FORMAT`

    This allows you to specify exactly what the rsync client outputs to the
    user on a per-update basis.  The format is a text string containing
    embedded single-character escape sequences prefixed with a percent (%)
    character.  A default format of "%n%L" is assumed if either `--info=name`
    or `-v` is specified (this tells you just the name of the file and, if the
    item is a link, where it points).  For a full list of the possible escape
    characters, see the "`log format`" setting in the rsyncd.conf manpage.

    Specifying the `--out-format` option implies the `--info=name` option,
    which will mention each file, dir, etc. that gets updated in a significant
    way (a transferred file, a recreated symlink/device, or a touched
    directory).  In addition, if the itemize-changes escape (%i) is included in
    the string (e.g. if the `--itemize-changes` option was used), the logging
    of names increases to mention any item that is changed in any way (as long
    as the receiving side is at least 2.6.4).  See the `--itemize-changes`
    option for a description of the output of "%i".

    Rsync will output the out-format string prior to a file's transfer unless
    one of the transfer-statistic escapes is requested, in which case the
    logging is done at the end of the file's transfer.  When this late logging
    is in effect and `--progress` is also specified, rsync will also output the
    name of the file being transferred prior to its progress information
    (followed, of course, by the out-format output).

0.  `--log-file=FILE`

    This option causes rsync to log what it is doing to a file.  This is
    similar to the logging that a daemon does, but can be requested for the
    client side and/or the server side of a non-daemon transfer.  If specified
    as a client option, transfer logging will be enabled with a default format
    of "%i %n%L".  See the `--log-file-format` option if you wish to override
    this.

    Here's a example command that requests the remote side to log what is
    happening:

    >     rsync -av --remote-option=--log-file=/tmp/rlog src/ dest/

    This is very useful if you need to debug why a connection is closing
    unexpectedly.

0.  `--log-file-format=FORMAT`

    This allows you to specify exactly what per-update logging is put into the
    file specified by the `--log-file` option (which must also be specified for
    this option to have any effect).  If you specify an empty string, updated
    files will not be mentioned in the log file.  For a list of the possible
    escape characters, see the "`log format`" setting in the rsyncd.conf manpage.

    The default FORMAT used if `--log-file` is specified and this option is not
    is '%i %n%L'.

0.  `--stats`

    This tells rsync to print a verbose set of statistics on the file transfer,
    allowing you to tell how effective rsync's delta-transfer algorithm is for
    your data.  This option is equivalent to `--info=stats2` if combined with 0
    or 1 `-v` options, or `--info=stats3` if combined with 2 or more `-v`
    options.

    The current statistics are as follows:

    - `Number of files` is the count of all "files" (in the generic sense),
      which includes directories, symlinks, etc.  The total count will be
      followed by a list of counts by filetype (if the total is non-zero).  For
      example: "(reg: 5, dir: 3, link: 2, dev: 1, special: 1)" lists the totals
      for regular files, directories, symlinks, devices, and special files.  If
      any of value is 0, it is completely omitted from the list.
    - `Number of created files` is the count of how many "files" (generic
      sense) were created (as opposed to updated).  The total count will be
      followed by a list of counts by filetype (if the total is non-zero).
    - `Number of deleted files` is the count of how many "files" (generic
      sense) were created (as opposed to updated).  The total count will be
      followed by a list of counts by filetype (if the total is non-zero).
      Note that this line is only output if deletions are in effect, and only
      if protocol 31 is being used (the default for rsync 3.1.x).
    - `Number of regular files transferred` is the count of normal files that
      were updated via rsync's delta-transfer algorithm, which does not include
      dirs, symlinks, etc.  Note that rsync 3.1.0 added the word "regular" into
      this heading.
    - `Total file size` is the total sum of all file sizes in the transfer.
      This does not count any size for directories or special files, but does
      include the size of symlinks.
    - `Total transferred file size` is the total sum of all files sizes for
      just the transferred files.
    - `Literal data` is how much unmatched file-update data we had to send to
      the receiver for it to recreate the updated files.
    - `Matched data` is how much data the receiver got locally when recreating
      the updated files.
    - `File list size` is how big the file-list data was when the sender sent
      it to the receiver.  This is smaller than the in-memory size for the file
      list due to some compressing of duplicated data when rsync sends the
      list.
    - `File list generation time` is the number of seconds that the sender
      spent creating the file list.  This requires a modern rsync on the
      sending side for this to be present.
    - `File list transfer time` is the number of seconds that the sender spent
      sending the file list to the receiver.
    - `Total bytes sent` is the count of all the bytes that rsync sent from the
      client side to the server side.
    - `Total bytes received` is the count of all non-message bytes that rsync
      received by the client side from the server side. "Non-message" bytes
      means that we don't count the bytes for a verbose message that the server
      sent to us, which makes the stats more consistent.

0.  `--8-bit-output`, `-8`

    This tells rsync to leave all high-bit characters unescaped in the output
    instead of trying to test them to see if they're valid in the current
    locale and escaping the invalid ones.  All control characters (but never
    tabs) are always escaped, regardless of this option's setting.

    The escape idiom that started in 2.6.7 is to output a literal backslash
    (`\`) and a hash (`#`), followed by exactly 3 octal digits.  For example, a
    newline would output as "`\#012`".  A literal backslash that is in a
    filename is not escaped unless it is followed by a hash and 3 digits (0-9).

0.  `--human-readable`, `-h`

    Output numbers in a more human-readable format.  There are 3 possible
    levels: (1) output numbers with a separator between each set of 3 digits
    (either a comma or a period, depending on if the decimal point is
    represented by a period or a comma); (2) output numbers in units of 1000
    (with a character suffix for larger units -- see below); (3) output
    numbers in units of 1024.

    The default is human-readable level 1.  Each `-h` option increases the
    level by one.  You can take the level down to 0 (to output numbers as pure
    digits) by specifying the `--no-human-readable` (`--no-h`) option.

    The unit letters that are appended in levels 2 and 3 are: K (kilo), M
    (mega), G (giga), or T (tera).  For example, a 1234567-byte file would
    output as 1.23M in level-2 (assuming that a period is your local decimal
    point).

    Backward compatibility note: versions of rsync prior to 3.1.0 do not
    support human-readable level 1, and they default to level 0.  Thus,
    specifying one or two `-h` options will behave in a comparable manner in
    old and new versions as long as you didn't specify a `--no-h` option prior
    to one or more `-h` options.  See the `--list-only` option for one
    difference.

0.  `--partial`

    By default, rsync will delete any partially transferred file if the
    transfer is interrupted.  In some circumstances it is more desirable to
    keep partially transferred files.  Using the `--partial` option tells rsync
    to keep the partial file which should make a subsequent transfer of the
    rest of the file much faster.

0.  `--partial-dir=DIR`

    A better way to keep partial files than the `--partial` option is to
    specify a _DIR_ that will be used to hold the partial data (instead of
    writing it out to the destination file).  On the next transfer, rsync will
    use a file found in this dir as data to speed up the resumption of the
    transfer and then delete it after it has served its purpose.

    Note that if `--whole-file` is specified (or implied), any partial-dir file
    that is found for a file that is being updated will simply be removed
    (since rsync is sending files without using rsync's delta-transfer
    algorithm).

    Rsync will create the _DIR_ if it is missing (just the last dir -- not the
    whole path).  This makes it easy to use a relative path (such as
    "`--partial-dir=.rsync-partial`") to have rsync create the
    partial-directory in the destination file's directory when needed, and then
    remove it again when the partial file is deleted.  Note that the directory
    is only removed if it is a relative pathname, as it is expected that an
    absolute path is to a directory that is reserved for partial-dir work.

    If the partial-dir value is not an absolute path, rsync will add an exclude
    rule at the end of all your existing excludes.  This will prevent the
    sending of any partial-dir files that may exist on the sending side, and
    will also prevent the untimely deletion of partial-dir items on the
    receiving side.  An example: the above `--partial-dir` option would add the
    equivalent of "`-f '-p .rsync-partial/'`" at the end of any other filter
    rules.

    If you are supplying your own exclude rules, you may need to add your own
    exclude/hide/protect rule for the partial-dir because (1) the auto-added
    rule may be ineffective at the end of your other rules, or (2) you may wish
    to override rsync's exclude choice.  For instance, if you want to make
    rsync clean-up any left-over partial-dirs that may be lying around, you
    should specify `--delete-after` and add a "risk" filter rule, e.g.
    `-f 'R .rsync-partial/'`. (Avoid using `--delete-before` or
    `--delete-during` unless you don't need rsync to use any of the left-over
    partial-dir data during the current run.)

    IMPORTANT: the `--partial-dir` should not be writable by other users or it
    is a security risk.  E.g. AVOID "/tmp".

    You can also set the partial-dir value the RSYNC_PARTIAL_DIR environment
    variable.  Setting this in the environment does not force `--partial` to be
    enabled, but rather it affects where partial files go when `--partial` is
    specified.  For instance, instead of using `--partial-dir=.rsync-tmp` along
    with `--progress`, you could set RSYNC_PARTIAL_DIR=.rsync-tmp in your
    environment and then just use the `-P` option to turn on the use of the
    .rsync-tmp dir for partial transfers.  The only times that the `--partial`
    option does not look for this environment value are (1) when `--inplace`
    was specified (since `--inplace` conflicts with `--partial-dir`), and (2)
    when `--delay-updates` was specified (see below).

    When a modern rsync resumes the transfer of a file in the partial-dir, that
    partial file is now updated in-place instead of creating yet another
    tmp-file copy (so it maxes out at dest + tmp instead of dest + partial +
    tmp).  This requires both ends of the transfer to be at least version
    3.2.0.

    For the purposes of the daemon-config's "`refuse options`" setting,
    `--partial-dir` does _not_ imply `--partial`.  This is so that a refusal of
    the `--partial` option can be used to disallow the overwriting of
    destination files with a partial transfer, while still allowing the safer
    idiom provided by `--partial-dir`.

0.  `--delay-updates`

    This option puts the temporary file from each updated file into a holding
    directory until the end of the transfer, at which time all the files are
    renamed into place in rapid succession.  This attempts to make the updating
    of the files a little more atomic.  By default the files are placed into a
    directory named `.~tmp~` in each file's destination directory, but if
    you've specified the `--partial-dir` option, that directory will be used
    instead.  See the comments in the `--partial-dir` section for a discussion
    of how this `.~tmp~` dir will be excluded from the transfer, and what you
    can do if you want rsync to cleanup old `.~tmp~` dirs that might be lying
    around.  Conflicts with `--inplace` and `--append`.

    This option uses more memory on the receiving side (one bit per file
    transferred) and also requires enough free disk space on the receiving side
    to hold an additional copy of all the updated files.  Note also that you
    should not use an absolute path to `--partial-dir` unless (1) there is no
    chance of any of the files in the transfer having the same name (since all
    the updated files will be put into a single directory if the path is
    absolute) and (2) there are no mount points in the hierarchy (since the
    delayed updates will fail if they can't be renamed into place).

    See also the "atomic-rsync" perl script in the "support" subdir for an
    update algorithm that is even more atomic (it uses `--link-dest` and a
    parallel hierarchy of files).

0.  `--prune-empty-dirs`, `-m`

    This option tells the receiving rsync to get rid of empty directories from
    the file-list, including nested directories that have no non-directory
    children.  This is useful for avoiding the creation of a bunch of useless
    directories when the sending rsync is recursively scanning a hierarchy of
    files using include/exclude/filter rules.

    Note that the use of transfer rules, such as the `--min-size` option, does
    not affect what goes into the file list, and thus does not leave
    directories empty, even if none of the files in a directory match the
    transfer rule.

    Because the file-list is actually being pruned, this option also affects
    what directories get deleted when a delete is active.  However, keep in
    mind that excluded files and directories can prevent existing items from
    being deleted due to an exclude both hiding source files and protecting
    destination files.  See the perishable filter-rule option for how to avoid
    this.

    You can prevent the pruning of certain empty directories from the file-list
    by using a global "protect" filter.  For instance, this option would ensure
    that the directory "emptydir" was kept in the file-list:

    >     --filter 'protect emptydir/'

    Here's an example that copies all .pdf files in a hierarchy, only creating
    the necessary destination directories to hold the .pdf files, and ensures
    that any superfluous files and directories in the destination are removed
    (note the hide filter of non-directories being used instead of an exclude):

    >     rsync -avm --del --include='*.pdf' -f 'hide,! */' src/ dest

    If you didn't want to remove superfluous destination files, the more
    time-honored options of `--include='*/' --exclude='*'` would work
    fine in place of the hide-filter (if that is more natural to you).

0.  `--progress`

    This option tells rsync to print information showing the progress of the
    transfer.  This gives a bored user something to watch.  With a modern rsync
    this is the same as specifying `--info=flist2,name,progress`, but any
    user-supplied settings for those info flags takes precedence (e.g.
    "`--info=flist0 --progress`").

    While rsync is transferring a regular file, it updates a progress line that
    looks like this:

    >     782448  63%  110.64kB/s    0:00:04

    In this example, the receiver has reconstructed 782448 bytes or 63% of the
    sender's file, which is being reconstructed at a rate of 110.64 kilobytes
    per second, and the transfer will finish in 4 seconds if the current rate
    is maintained until the end.

    These statistics can be misleading if rsync's delta-transfer algorithm is
    in use.  For example, if the sender's file consists of the basis file
    followed by additional data, the reported rate will probably drop
    dramatically when the receiver gets to the literal data, and the transfer
    will probably take much longer to finish than the receiver estimated as it
    was finishing the matched part of the file.

    When the file transfer finishes, rsync replaces the progress line with a
    summary line that looks like this:

    >     1,238,099 100%  146.38kB/s    0:00:08  (xfr#5, to-chk=169/396)

    In this example, the file was 1,238,099 bytes long in total, the average
    rate of transfer for the whole file was 146.38 kilobytes per second over
    the 8 seconds that it took to complete, it was the 5th transfer of a
    regular file during the current rsync session, and there are 169 more files
    for the receiver to check (to see if they are up-to-date or not) remaining
    out of the 396 total files in the file-list.

    In an incremental recursion scan, rsync won't know the total number of
    files in the file-list until it reaches the ends of the scan, but since it
    starts to transfer files during the scan, it will display a line with the
    text "ir-chk" (for incremental recursion check) instead of "to-chk" until
    the point that it knows the full size of the list, at which point it will
    switch to using "to-chk".  Thus, seeing "ir-chk" lets you know that the
    total count of files in the file list is still going to increase (and each
    time it does, the count of files left to check will increase by the number
    of the files added to the list).

0.  `-P`

    The `-P` option is equivalent to `--partial --progress`.  Its purpose is
    to make it much easier to specify these two options for a long transfer
    that may be interrupted.

    There is also a `--info=progress2` option that outputs statistics based on
    the whole transfer, rather than individual files.  Use this flag without
    outputting a filename (e.g. avoid `-v` or specify `--info=name0`) if you
    want to see how the transfer is doing without scrolling the screen with a
    lot of names. (You don't need to specify the `--progress` option in order
    to use `--info=progress2`.)

    Finally, you can get an instant progress report by sending rsync a signal
    of either SIGINFO or SIGVTALRM.  On BSD systems, a SIGINFO is generated by
    typing a Ctrl+T (Linux doesn't currently support a SIGINFO signal).  When
    the client-side process receives one of those signals, it sets a flag to
    output a single progress report which is output when the current file
    transfer finishes (so it may take a little time if a big file is being
    handled when the signal arrives).  A filename is output (if needed)
    followed by the `--info=progress2` format of progress info.  If you don't
    know which of the 3 rsync processes is the client process, it's OK to
    signal all of them (since the non-client processes ignore the signal).

    CAUTION: sending SIGVTALRM to an older rsync (pre-3.2.0) will kill it.

0.  `--password-file=FILE`

    This option allows you to provide a password for accessing an rsync daemon
    via a file or via standard input if **FILE** is `-`.  The file should
    contain just the password on the first line (all other lines are ignored).
    Rsync will exit with an error if **FILE** is world readable or if a
    root-run rsync command finds a non-root-owned file.

    This option does not supply a password to a remote shell transport such as
    ssh; to learn how to do that, consult the remote shell's documentation.
    When accessing an rsync daemon using a remote shell as the transport, this
    option only comes into effect after the remote shell finishes its
    authentication (i.e. if you have also specified a password in the daemon's
    config file).

0.  `--early-input=FILE`

    This option allows rsync to send up to 5K of data to the "early exec"
    script on its stdin.  One possible use of this data is to give the script a
    secret that can be used to mount an encrypted filesystem (which you should
    unmount in the the "post-xfer exec" script).

    The daemon must be at least version 3.2.1.

0.  `--list-only`

    This option will cause the source files to be listed instead of
    transferred.  This option is inferred if there is a single source arg and
    no destination specified, so its main uses are: (1) to turn a copy command
    that includes a destination arg into a file-listing command, or (2) to be
    able to specify more than one source arg (note: be sure to include the
    destination).  Caution: keep in mind that a source arg with a wild-card is
    expanded by the shell into multiple args, so it is never safe to try to
    list such an arg without using this option. For example:

    >     rsync -av --list-only foo* dest/

    Starting with rsync 3.1.0, the sizes output by `--list-only` are affected
    by the `--human-readable` option.  By default they will contain digit
    separators, but higher levels of readability will output the sizes with
    unit suffixes.  Note also that the column width for the size output has
    increased from 11 to 14 characters for all human-readable levels.  Use
    `--no-h` if you want just digits in the sizes, and the old column width of
    11 characters.

    Compatibility note: when requesting a remote listing of files from an rsync
    that is version 2.6.3 or older, you may encounter an error if you ask for a
    non-recursive listing.  This is because a file listing implies the `--dirs`
    option w/o `--recursive`, and older rsyncs don't have that option.  To
    avoid this problem, either specify the `--no-dirs` option (if you don't
    need to expand a directory's content), or turn on recursion and exclude the
    content of subdirectories: `-r --exclude='/*/*'`.

0.  `--bwlimit=RATE`

    This option allows you to specify the maximum transfer rate for the data
    sent over the socket, specified in units per second.  The RATE value can be
    suffixed with a string to indicate a size multiplier, and may be a
    fractional value (e.g. "`--bwlimit=1.5m`").  If no suffix is specified, the
    value will be assumed to be in units of 1024 bytes (as if "K" or "KiB" had
    been appended).  See the `--max-size` option for a description of all the
    available suffixes.  A value of zero specifies no limit.

    For backward-compatibility reasons, the rate limit will be rounded to the
    nearest KiB unit, so no rate smaller than 1024 bytes per second is
    possible.

    Rsync writes data over the socket in blocks, and this option both limits
    the size of the blocks that rsync writes, and tries to keep the average
    transfer rate at the requested limit.  Some burstiness may be seen where
    rsync writes out a block of data and then sleeps to bring the average rate
    into compliance.

    Due to the internal buffering of data, the `--progress` option may not be
    an accurate reflection on how fast the data is being sent.  This is because
    some files can show up as being rapidly sent when the data is quickly
    buffered, while other can show up as very slow when the flushing of the
    output buffer occurs.  This may be fixed in a future version.

0.  `--write-batch=FILE`

    Record a file that can later be applied to another identical destination
    with `--read-batch`.  See the "BATCH MODE" section for details, and also
    the `--only-write-batch` option.

    This option overrides the negotiated checksum & compress lists and always
    negotiates a choice based on old-school md5/md4/zlib choices.  If you want
    a more modern choice, use the `--checksum-choice` (`--cc`) and/or
    `--compress-choice` (`--zc`) options.

0.  `--only-write-batch=FILE`

    Works like `--write-batch`, except that no updates are made on the
    destination system when creating the batch.  This lets you transport the
    changes to the destination system via some other means and then apply the
    changes via `--read-batch`.

    Note that you can feel free to write the batch directly to some portable
    media: if this media fills to capacity before the end of the transfer, you
    can just apply that partial transfer to the destination and repeat the
    whole process to get the rest of the changes (as long as you don't mind a
    partially updated destination system while the multi-update cycle is
    happening).

    Also note that you only save bandwidth when pushing changes to a remote
    system because this allows the batched data to be diverted from the sender
    into the batch file without having to flow over the wire to the receiver
    (when pulling, the sender is remote, and thus can't write the batch).

0.  `--read-batch=FILE`

    Apply all of the changes stored in FILE, a file previously generated by
    `--write-batch`.  If _FILE_ is `-`, the batch data will be read from
    standard input. See the "BATCH MODE" section for details.

0.  `--protocol=NUM`

    Force an older protocol version to be used.  This is useful for creating a
    batch file that is compatible with an older version of rsync.  For
    instance, if rsync 2.6.4 is being used with the `--write-batch` option, but
    rsync 2.6.3 is what will be used to run the `--read-batch` option, you
    should use "--protocol=28" when creating the batch file to force the older
    protocol version to be used in the batch file (assuming you can't upgrade
    the rsync on the reading system).

0.  `--iconv=CONVERT_SPEC`

    Rsync can convert filenames between character sets using this option.
    Using a CONVERT_SPEC of "." tells rsync to look up the default
    character-set via the locale setting.  Alternately, you can fully specify
    what conversion to do by giving a local and a remote charset separated by a
    comma in the order `--iconv=LOCAL,REMOTE`, e.g. `--iconv=utf8,iso88591`.
    This order ensures that the option will stay the same whether you're
    pushing or pulling files.  Finally, you can specify either `--no-iconv` or
    a CONVERT_SPEC of "-" to turn off any conversion.  The default setting of
    this option is site-specific, and can also be affected via the RSYNC_ICONV
    environment variable.

    For a list of what charset names your local iconv library supports, you can
    run "`iconv --list`".

    If you specify the `--protect-args` option (`-s`), rsync will translate the
    filenames you specify on the command-line that are being sent to the remote
    host.  See also the `--files-from` option.

    Note that rsync does not do any conversion of names in filter files
    (including include/exclude files).  It is up to you to ensure that you're
    specifying matching rules that can match on both sides of the transfer.
    For instance, you can specify extra include/exclude rules if there are
    filename differences on the two sides that need to be accounted for.

    When you pass an `--iconv` option to an rsync daemon that allows it, the
    daemon uses the charset specified in its "charset" configuration parameter
    regardless of the remote charset you actually pass.  Thus, you may feel
    free to specify just the local charset for a daemon transfer (e.g.
    `--iconv=utf8`).

0.  `--ipv4`, `-4` or `--ipv6`, `-6`

    Tells rsync to prefer IPv4/IPv6 when creating sockets or running ssh.  This
    affects sockets that rsync has direct control over, such as the outgoing
    socket when directly contacting an rsync daemon, as well as the forwarding
    of the `-4` or `-6` option to ssh when rsync can deduce that ssh is being
    used as the remote shell.  For other remote shells you'll need to specify
    the "`--rsh SHELL -4`" option directly (or whatever ipv4/ipv6 hint options
    it uses).

    These options also exist in the `--daemon` mode section.

    If rsync was complied without support for IPv6, the `--ipv6` option will
    have no effect.  The `rsync -V` output will contain "`no IPv6`" if is the
    case.

0.  `--checksum-seed=NUM`

    Set the checksum seed to the integer NUM.  This 4 byte checksum seed is
    included in each block and MD4 file checksum calculation (the more modern
    MD5 file checksums don't use a seed).  By default the checksum seed is
    generated by the server and defaults to the current **time**().  This
    option is used to set a specific checksum seed, which is useful for
    applications that want repeatable block checksums, or in the case where the
    user wants a more random checksum seed.  Setting NUM to 0 causes rsync to
    use the default of **time**() for checksum seed.

# DAEMON OPTIONS

The options allowed when starting an rsync daemon are as follows:

0.  `--daemon`

    This tells rsync that it is to run as a daemon.  The daemon you start
    running may be accessed using an rsync client using the `host::module` or
    `rsync://host/module/` syntax.

    If standard input is a socket then rsync will assume that it is being run
    via inetd, otherwise it will detach from the current terminal and become a
    background daemon.  The daemon will read the config file (rsyncd.conf) on
    each connect made by a client and respond to requests accordingly.  See the
    **rsyncd.conf**(5) man page for more details.

0.  `--address=ADDRESS`

    By default rsync will bind to the wildcard address when run as a daemon
    with the `--daemon` option.  The `--address` option allows you to specify a
    specific IP address (or hostname) to bind to.  This makes virtual hosting
    possible in conjunction with the `--config` option.  See also the "address"
    global option in the rsyncd.conf manpage.

0.  `--bwlimit=RATE`

    This option allows you to specify the maximum transfer rate for the data
    the daemon sends over the socket.  The client can still specify a smaller
    `--bwlimit` value, but no larger value will be allowed.  See the client
    version of this option (above) for some extra details.

0.  `--config=FILE`

    This specifies an alternate config file than the default.  This is only
    relevant when `--daemon` is specified.  The default is /etc/rsyncd.conf
    unless the daemon is running over a remote shell program and the remote
    user is not the super-user; in that case the default is rsyncd.conf in the
    current directory (typically $HOME).

0.  `--dparam=OVERRIDE`, `-M`

    This option can be used to set a daemon-config parameter when starting up
    rsync in daemon mode.  It is equivalent to adding the parameter at the end
    of the global settings prior to the first module's definition.  The
    parameter names can be specified without spaces, if you so desire.  For
    instance:

    >     rsync --daemon -M pidfile=/path/rsync.pid

0.  `--no-detach`

    When running as a daemon, this option instructs rsync to not detach itself
    and become a background process.  This option is required when running as a
    service on Cygwin, and may also be useful when rsync is supervised by a
    program such as `daemontools` or AIX's `System Resource Controller`.
    `--no-detach` is also recommended when rsync is run under a debugger.  This
    option has no effect if rsync is run from inetd or sshd.

0.  `--port=PORT`

    This specifies an alternate TCP port number for the daemon to listen on
    rather than the default of 873.  See also the "port" global option in the
    rsyncd.conf manpage.

0.  `--log-file=FILE`

    This option tells the rsync daemon to use the given log-file name instead
    of using the "`log file`" setting in the config file.

0.  `--log-file-format=FORMAT`

    This option tells the rsync daemon to use the given FORMAT string instead
    of using the "`log format`" setting in the config file.  It also enables
    "`transfer logging`" unless the string is empty, in which case transfer
    logging is turned off.

0.  `--sockopts`

    This overrides the `socket options` setting in the rsyncd.conf file and has
    the same syntax.

0.  `--verbose`, `-v`

    This option increases the amount of information the daemon logs during its
    startup phase.  After the client connects, the daemon's verbosity level
    will be controlled by the options that the client used and the
    "`max verbosity`" setting in the module's config section.

0.  `--ipv4`, `-4` or `--ipv6`, `-6`

    Tells rsync to prefer IPv4/IPv6 when creating the incoming sockets that the
    rsync daemon will use to listen for connections.  One of these options may
    be required in older versions of Linux to work around an IPv6 bug in the
    kernel (if you see an "address already in use" error when nothing else is
    using the port, try specifying `--ipv6` or `--ipv4` when starting the
    daemon).

    These options also exist in the regular rsync options section.

    If rsync was complied without support for IPv6, the `--ipv6` option will
    have no effect.  The `rsync -V` output will contain "`no IPv6`" if is the
    case.

0.  `--help`, `-h`

    When specified after `--daemon`, print a short help page describing the
    options available for starting an rsync daemon.

# FILTER RULES

The filter rules allow for flexible selection of which files to transfer
(include) and which files to skip (exclude).  The rules either directly specify
include/exclude patterns or they specify a way to acquire more include/exclude
patterns (e.g. to read them from a file).

As the list of files/directories to transfer is built, rsync checks each name
to be transferred against the list of include/exclude patterns in turn, and the
first matching pattern is acted on: if it is an exclude pattern, then that file
is skipped; if it is an include pattern then that filename is not skipped; if
no matching pattern is found, then the filename is not skipped.

Rsync builds an ordered list of filter rules as specified on the command-line.
Filter rules have the following syntax:

>     RULE [PATTERN_OR_FILENAME]
>     RULE,MODIFIERS [PATTERN_OR_FILENAME]

You have your choice of using either short or long RULE names, as described
below.  If you use a short-named rule, the ',' separating the RULE from the
MODIFIERS is optional.  The PATTERN or FILENAME that follows (when present)
must come after either a single space or an underscore (\_).  Here are the
available rule prefixes:

0.  `exclude, '-'` specifies an exclude pattern.
0.  `include, '+'` specifies an include pattern.
0.  `merge, '.'` specifies a merge-file to read for more rules.
0.  `dir-merge, ':'` specifies a per-directory merge-file.
0.  `hide, 'H'` specifies a pattern for hiding files from the transfer.
0.  `show, 'S'` files that match the pattern are not hidden.
0.  `protect, 'P'` specifies a pattern for protecting files from deletion.
0.  `risk, 'R'` files that match the pattern are not protected.
0.  `clear, '!'` clears the current include/exclude list (takes no arg)

When rules are being read from a file, empty lines are ignored, as are comment
lines that start with a "#".

[comment]: # (Remember that markdown strips spaces from start/end of ` ... ` sequences!)
[comment]: # (Thus, the `x ` sequences below use a literal non-breakable space!)

Note that the `--include` & `--exclude` command-line options do not allow the
full range of rule parsing as described above -- they only allow the
specification of include / exclude patterns plus a "`!`" token to clear the
list (and the normal comment parsing when rules are read from a file).  If a
pattern does not begin with "`- `" (dash, space) or "`+ `" (plus, space), then
the rule will be interpreted as if "`+ `" (for an include option) or "`- `"
(for an exclude option) were prefixed to the string.  A `--filter` option, on
the other hand, must always contain either a short or long rule name at the
start of the rule.

Note also that the `--filter`, `--include`, and `--exclude` options take one
rule/pattern each.  To add multiple ones, you can repeat the options on the
command-line, use the merge-file syntax of the `--filter` option, or the
`--include-from` / `--exclude-from` options.

# INCLUDE/EXCLUDE PATTERN RULES

You can include and exclude files by specifying patterns using the "+", "-",
etc. filter rules (as introduced in the FILTER RULES section above).  The
include/exclude rules each specify a pattern that is matched against the names
of the files that are going to be transferred.  These patterns can take several
forms:

- if the pattern starts with a `/` then it is anchored to a particular spot in
  the hierarchy of files, otherwise it is matched against the end of the
  pathname.  This is similar to a leading `^` in regular expressions.  Thus
  `/foo` would match a name of "foo" at either the "root of the transfer" (for
  a global rule) or in the merge-file's directory (for a per-directory rule).
  An unqualified `foo` would match a name of "foo" anywhere in the tree because
  the algorithm is applied recursively from the top down; it behaves as if each
  path component gets a turn at being the end of the filename.  Even the
  unanchored "sub/foo" would match at any point in the hierarchy where a "foo"
  was found within a directory named "sub".  See the section on ANCHORING
  INCLUDE/EXCLUDE PATTERNS for a full discussion of how to specify a pattern
  that matches at the root of the transfer.
- if the pattern ends with a `/` then it will only match a directory, not a
  regular file, symlink, or device.
- rsync chooses between doing a simple string match and wildcard matching by
  checking if the pattern contains one of these three wildcard characters:
  '`*`', '`?`', and '`[`' .
- a '`*`' matches any path component, but it stops at slashes.
- use '`**`' to match anything, including slashes.
- a '`?`' matches any character except a slash (`/`).
- a '`[`' introduces a character class, such as `[a-z]` or `[[:alpha:]]`.
- in a wildcard pattern, a backslash can be used to escape a wildcard
  character, but it is matched literally when no wildcards are present.  This
  means that there is an extra level of backslash removal when a pattern
  contains wildcard characters compared to a pattern that has none.  e.g. if
  you add a wildcard to "`foo\bar`" (which matches the backslash) you would
  need to use "`foo\\bar*`" to avoid the "`\b`" becoming just "b".
- if the pattern contains a `/` (not counting a trailing /) or a "`**`", then it
  is matched against the full pathname, including any leading directories.  If
  the pattern doesn't contain a `/` or a "`**`", then it is matched only against
  the final component of the filename. (Remember that the algorithm is applied
  recursively so "full filename" can actually be any portion of a path from the
  starting directory on down.)
- a trailing "`dir_name/***`" will match both the directory (as if "dir_name/"
  had been specified) and everything in the directory (as if "`dir_name/**`"
  had been specified).  This behavior was added in version 2.6.7.

Note that, when using the `--recursive` (`-r`) option (which is implied by
`-a`), every subdir component of every path is visited left to right, with each
directory having a chance for exclusion before its content.  In this way
include/exclude patterns are applied recursively to the pathname of each node
in the filesystem's tree (those inside the transfer).  The exclude patterns
short-circuit the directory traversal stage as rsync finds the files to send.

For instance, to include "`/foo/bar/baz`", the directories "`/foo`" and "`/foo/bar`"
must not be excluded.  Excluding one of those parent directories prevents the
examination of its content, cutting off rsync's recursion into those paths and
rendering the include for "`/foo/bar/baz`" ineffectual (since rsync can't match
something it never sees in the cut-off section of the directory hierarchy).

The concept path exclusion is particularly important when using a trailing '`*`'
rule.  For instance, this won't work:

>     + /some/path/this-file-will-not-be-found
>     + /file-is-included
>     - *

This fails because the parent directory "some" is excluded by the '`*`' rule, so
rsync never visits any of the files in the "some" or "some/path" directories.
One solution is to ask for all directories in the hierarchy to be included by
using a single rule: "`+ */`" (put it somewhere before the "`- *`" rule), and
perhaps use the `--prune-empty-dirs` option.  Another solution is to add
specific include rules for all the parent dirs that need to be visited.  For
instance, this set of rules works fine:

>     + /some/
>     + /some/path/
>     + /some/path/this-file-is-found
>     + /file-also-included
>     - *

Here are some examples of exclude/include matching:

- "`- *.o`" would exclude all names matching `*.o`
- "`- /foo`" would exclude a file (or directory) named foo in the transfer-root
  directory
- "`- foo/`" would exclude any directory named foo
- "`- /foo/*/bar`" would exclude any file named bar which is at two levels
  below a directory named foo in the transfer-root directory
- "`- /foo/**/bar`" would exclude any file named bar two or more levels below a
  directory named foo in the transfer-root directory
- The combination of "`+ */`", "`+ *.c`", and "`- *`" would include all
  directories and C source files but nothing else (see also the
  `--prune-empty-dirs` option)
- The combination of "`+ foo/`", "`+ foo/bar.c`", and "`- *`" would include
  only the foo directory and foo/bar.c (the foo directory must be explicitly
  included or it would be excluded by the "`*`")

The following modifiers are accepted after a "`+`" or "`-`":

- A `/` specifies that the include/exclude rule should be matched against the
  absolute pathname of the current item.  For example, "`-/ /etc/passwd`" would
  exclude the passwd file any time the transfer was sending files from the
  "/etc" directory, and "-/ subdir/foo" would always exclude "foo" when it is
  in a dir named "subdir", even if "foo" is at the root of the current
  transfer.
- A `!` specifies that the include/exclude should take effect if the pattern
  fails to match.  For instance, "`-! */`" would exclude all non-directories.
- A `C` is used to indicate that all the global CVS-exclude rules should be
  inserted as excludes in place of the "-C".  No arg should follow.
- An `s` is used to indicate that the rule applies to the sending side.  When a
  rule affects the sending side, it prevents files from being transferred.  The
  default is for a rule to affect both sides unless `--delete-excluded` was
  specified, in which case default rules become sender-side only.  See also the
  hide (H) and show (S) rules, which are an alternate way to specify
  sending-side includes/excludes.
- An `r` is used to indicate that the rule applies to the receiving side.  When
  a rule affects the receiving side, it prevents files from being deleted.  See
  the `s` modifier for more info.  See also the protect (P) and risk (R) rules,
  which are an alternate way to specify receiver-side includes/excludes.
- A `p` indicates that a rule is perishable, meaning that it is ignored in
  directories that are being deleted.  For instance, the `-C` option's default
  rules that exclude things like "CVS" and "`*.o`" are marked as perishable,
  and will not prevent a directory that was removed on the source from being
  deleted on the destination.
- An `x` indicates that a rule affects xattr names in xattr copy/delete
  operations (and is thus ignored when matching file/dir names).  If no
  xattr-matching rules are specified, a default xattr filtering rule is used
  (see the `--xattrs` option).

# MERGE-FILE FILTER RULES

You can merge whole files into your filter rules by specifying either a merge
(.) or a dir-merge (:) filter rule (as introduced in the FILTER RULES section
above).

There are two kinds of merged files -- single-instance ('.') and per-directory
(':').  A single-instance merge file is read one time, and its rules are
incorporated into the filter list in the place of the "." rule.  For
per-directory merge files, rsync will scan every directory that it traverses
for the named file, merging its contents when the file exists into the current
list of inherited rules.  These per-directory rule files must be created on the
sending side because it is the sending side that is being scanned for the
available files to transfer.  These rule files may also need to be transferred
to the receiving side if you want them to affect what files don't get deleted
(see PER-DIRECTORY RULES AND DELETE below).

Some examples:

>     merge /etc/rsync/default.rules
>     . /etc/rsync/default.rules
>     dir-merge .per-dir-filter
>     dir-merge,n- .non-inherited-per-dir-excludes
>     :n- .non-inherited-per-dir-excludes

The following modifiers are accepted after a merge or dir-merge rule:

- A `-` specifies that the file should consist of only exclude patterns, with
  no other rule-parsing except for in-file comments.
- A `+` specifies that the file should consist of only include patterns, with
  no other rule-parsing except for in-file comments.
- A `C` is a way to specify that the file should be read in a CVS-compatible
  manner.  This turns on 'n', 'w', and '-', but also allows the list-clearing
  token (!) to be specified.  If no filename is provided, ".cvsignore" is
  assumed.
- A `e` will exclude the merge-file name from the transfer; e.g.  "dir-merge,e
  .rules" is like "dir-merge .rules" and "- .rules".
- An `n` specifies that the rules are not inherited by subdirectories.
- A `w` specifies that the rules are word-split on whitespace instead of the
  normal line-splitting.  This also turns off comments.  Note: the space that
  separates the prefix from the rule is treated specially, so "- foo + bar" is
  parsed as two rules (assuming that prefix-parsing wasn't also disabled).
- You may also specify any of the modifiers for the "+" or "-" rules (above) in
  order to have the rules that are read in from the file default to having that
  modifier set (except for the `!` modifier, which would not be useful).  For
  instance, "merge,-/ .excl" would treat the contents of .excl as absolute-path
  excludes, while "dir-merge,s .filt" and ":sC" would each make all their
  per-directory rules apply only on the sending side.  If the merge rule
  specifies sides to affect (via the `s` or `r` modifier or both), then the
  rules in the file must not specify sides (via a modifier or a rule prefix
  such as `hide`).

Per-directory rules are inherited in all subdirectories of the directory where
the merge-file was found unless the 'n' modifier was used.  Each subdirectory's
rules are prefixed to the inherited per-directory rules from its parents, which
gives the newest rules a higher priority than the inherited rules.  The entire
set of dir-merge rules are grouped together in the spot where the merge-file
was specified, so it is possible to override dir-merge rules via a rule that
got specified earlier in the list of global rules.  When the list-clearing rule
("!") is read from a per-directory file, it only clears the inherited rules for
the current merge file.

Another way to prevent a single rule from a dir-merge file from being inherited
is to anchor it with a leading slash.  Anchored rules in a per-directory
merge-file are relative to the merge-file's directory, so a pattern "/foo"
would only match the file "foo" in the directory where the dir-merge filter
file was found.

Here's an example filter file which you'd specify via `--filter=". file":`

>     merge /home/user/.global-filter
>     - *.gz
>     dir-merge .rules
>     + *.[ch]
>     - *.o
>     - foo*

This will merge the contents of the /home/user/.global-filter file at the start
of the list and also turns the ".rules" filename into a per-directory filter
file.  All rules read in prior to the start of the directory scan follow the
global anchoring rules (i.e. a leading slash matches at the root of the
transfer).

If a per-directory merge-file is specified with a path that is a parent
directory of the first transfer directory, rsync will scan all the parent dirs
from that starting point to the transfer directory for the indicated
per-directory file.  For instance, here is a common filter (see `-F`):

>     --filter=': /.rsync-filter'

That rule tells rsync to scan for the file .rsync-filter in all directories
from the root down through the parent directory of the transfer prior to the
start of the normal directory scan of the file in the directories that are sent
as a part of the transfer. (Note: for an rsync daemon, the root is always the
same as the module's "path".)

Some examples of this pre-scanning for per-directory files:

>     rsync -avF /src/path/ /dest/dir
>     rsync -av --filter=': ../../.rsync-filter' /src/path/ /dest/dir
>     rsync -av --filter=': .rsync-filter' /src/path/ /dest/dir

The first two commands above will look for ".rsync-filter" in "/" and "/src"
before the normal scan begins looking for the file in "/src/path" and its
subdirectories.  The last command avoids the parent-dir scan and only looks for
the ".rsync-filter" files in each directory that is a part of the transfer.

If you want to include the contents of a ".cvsignore" in your patterns, you
should use the rule ":C", which creates a dir-merge of the .cvsignore file, but
parsed in a CVS-compatible manner.  You can use this to affect where the
`--cvs-exclude` (`-C`) option's inclusion of the per-directory .cvsignore file
gets placed into your rules by putting the ":C" wherever you like in your
filter rules.  Without this, rsync would add the dir-merge rule for the
.cvsignore file at the end of all your other rules (giving it a lower priority
than your command-line rules).  For example:

> ```
> cat <<EOT | rsync -avC --filter='. -' a/ b
> + foo.o
> :C
> - *.old
> EOT
> rsync -avC --include=foo.o -f :C --exclude='*.old' a/ b
> ```

Both of the above rsync commands are identical.  Each one will merge all the
per-directory .cvsignore rules in the middle of the list rather than at the
end.  This allows their dir-specific rules to supersede the rules that follow
the :C instead of being subservient to all your rules.  To affect the other CVS
exclude rules (i.e. the default list of exclusions, the contents of
$HOME/.cvsignore, and the value of $CVSIGNORE) you should omit the `-C`
command-line option and instead insert a "-C" rule into your filter rules; e.g.
"`--filter=-C`".

# LIST-CLEARING FILTER RULE

You can clear the current include/exclude list by using the "!" filter rule (as
introduced in the FILTER RULES section above).  The "current" list is either
the global list of rules (if the rule is encountered while parsing the filter
options) or a set of per-directory rules (which are inherited in their own
sub-list, so a subdirectory can use this to clear out the parent's rules).

# ANCHORING INCLUDE/EXCLUDE PATTERNS

As mentioned earlier, global include/exclude patterns are anchored at the "root
of the transfer" (as opposed to per-directory patterns, which are anchored at
the merge-file's directory).  If you think of the transfer as a subtree of
names that are being sent from sender to receiver, the transfer-root is where
the tree starts to be duplicated in the destination directory.  This root
governs where patterns that start with a / match.

Because the matching is relative to the transfer-root, changing the trailing
slash on a source path or changing your use of the `--relative` option affects
the path you need to use in your matching (in addition to changing how much of
the file tree is duplicated on the destination host).  The following examples
demonstrate this.

Let's say that we want to match two source files, one with an absolute
path of "/home/me/foo/bar", and one with a path of "/home/you/bar/baz".
Here is how the various command choices differ for a 2-source transfer:

> ```
> Example cmd: rsync -a /home/me /home/you /dest
> +/- pattern: /me/foo/bar
> +/- pattern: /you/bar/baz
> Target file: /dest/me/foo/bar
> Target file: /dest/you/bar/baz
> ```

> ```
> Example cmd: rsync -a /home/me/ /home/you/ /dest
> +/- pattern: /foo/bar               (note missing "me")
> +/- pattern: /bar/baz               (note missing "you")
> Target file: /dest/foo/bar
> Target file: /dest/bar/baz
> ```

> ```
> Example cmd: rsync -a --relative /home/me/ /home/you /dest
> +/- pattern: /home/me/foo/bar       (note full path)
> +/- pattern: /home/you/bar/baz      (ditto)
> Target file: /dest/home/me/foo/bar
> Target file: /dest/home/you/bar/baz
> ```

> ```
> Example cmd: cd /home; rsync -a --relative me/foo you/ /dest
> +/- pattern: /me/foo/bar      (starts at specified path)
> +/- pattern: /you/bar/baz     (ditto)
> Target file: /dest/me/foo/bar
> Target file: /dest/you/bar/baz
> ```

The easiest way to see what name you should filter is to just
look at the output when using `--verbose` and put a / in front of the name
(use the `--dry-run` option if you're not yet ready to copy any files).

# PER-DIRECTORY RULES AND DELETE

Without a delete option, per-directory rules are only relevant on the sending
side, so you can feel free to exclude the merge files themselves without
affecting the transfer.  To make this easy, the 'e' modifier adds this exclude
for you, as seen in these two equivalent commands:

>     rsync -av --filter=': .excl' --exclude=.excl host:src/dir /dest
>     rsync -av --filter=':e .excl' host:src/dir /dest

However, if you want to do a delete on the receiving side AND you want some
files to be excluded from being deleted, you'll need to be sure that the
receiving side knows what files to exclude.  The easiest way is to include the
per-directory merge files in the transfer and use `--delete-after`, because
this ensures that the receiving side gets all the same exclude rules as the
sending side before it tries to delete anything:

>     rsync -avF --delete-after host:src/dir /dest

However, if the merge files are not a part of the transfer, you'll need to
either specify some global exclude rules (i.e. specified on the command line),
or you'll need to maintain your own per-directory merge files on the receiving
side.  An example of the first is this (assume that the remote .rules files
exclude themselves):

>     rsync -av --filter=': .rules' --filter='. /my/extra.rules'
>        --delete host:src/dir /dest

In the above example the extra.rules file can affect both sides of the
transfer, but (on the sending side) the rules are subservient to the rules
merged from the .rules files because they were specified after the
per-directory merge rule.

In one final example, the remote side is excluding the .rsync-filter files from
the transfer, but we want to use our own .rsync-filter files to control what
gets deleted on the receiving side.  To do this we must specifically exclude
the per-directory merge files (so that they don't get deleted) and then put
rules into the local files to control what else should not get deleted.  Like
one of these commands:

> ```
> rsync -av --filter=':e /.rsync-filter' --delete \
>     host:src/dir /dest
> rsync -avFF --delete host:src/dir /dest
> ```

# BATCH MODE

Batch mode can be used to apply the same set of updates to many identical
systems.  Suppose one has a tree which is replicated on a number of hosts.  Now
suppose some changes have been made to this source tree and those changes need
to be propagated to the other hosts.  In order to do this using batch mode,
rsync is run with the write-batch option to apply the changes made to the
source tree to one of the destination trees.  The write-batch option causes the
rsync client to store in a "batch file" all the information needed to repeat
this operation against other, identical destination trees.

Generating the batch file once saves having to perform the file status,
checksum, and data block generation more than once when updating multiple
destination trees.  Multicast transport protocols can be used to transfer the
batch update files in parallel to many hosts at once, instead of sending the
same data to every host individually.

To apply the recorded changes to another destination tree, run rsync with the
read-batch option, specifying the name of the same batch file, and the
destination tree.  Rsync updates the destination tree using the information
stored in the batch file.

For your convenience, a script file is also created when the write-batch option
is used: it will be named the same as the batch file with ".sh" appended.  This
script file contains a command-line suitable for updating a destination tree
using the associated batch file.  It can be executed using a Bourne (or
Bourne-like) shell, optionally passing in an alternate destination tree
pathname which is then used instead of the original destination path.  This is
useful when the destination tree path on the current host differs from the one
used to create the batch file.

Examples:

>     $ rsync --write-batch=foo -a host:/source/dir/ /adest/dir/
>     $ scp foo* remote:
>     $ ssh remote ./foo.sh /bdest/dir/

>     $ rsync --write-batch=foo -a /source/dir/ /adest/dir/
>     $ ssh remote rsync --read-batch=- -a /bdest/dir/ <foo

In these examples, rsync is used to update /adest/dir/ from /source/dir/ and
the information to repeat this operation is stored in "foo" and "foo.sh".  The
host "remote" is then updated with the batched data going into the directory
/bdest/dir.  The differences between the two examples reveals some of the
flexibility you have in how you deal with batches:

- The first example shows that the initial copy doesn't have to be local -- you
  can push or pull data to/from a remote host using either the remote-shell
  syntax or rsync daemon syntax, as desired.
- The first example uses the created "foo.sh" file to get the right rsync
  options when running the read-batch command on the remote host.
- The second example reads the batch data via standard input so that the batch
  file doesn't need to be copied to the remote machine first.  This example
  avoids the foo.sh script because it needed to use a modified `--read-batch`
  option, but you could edit the script file if you wished to make use of it
  (just be sure that no other option is trying to use standard input, such as
  the "`--exclude-from=-`" option).

Caveats:

The read-batch option expects the destination tree that it is updating to be
identical to the destination tree that was used to create the batch update
fileset.  When a difference between the destination trees is encountered the
update might be discarded with a warning (if the file appears to be up-to-date
already) or the file-update may be attempted and then, if the file fails to
verify, the update discarded with an error.  This means that it should be safe
to re-run a read-batch operation if the command got interrupted.  If you wish
to force the batched-update to always be attempted regardless of the file's
size and date, use the `-I` option (when reading the batch).  If an error
occurs, the destination tree will probably be in a partially updated state.  In
that case, rsync can be used in its regular (non-batch) mode of operation to
fix up the destination tree.

The rsync version used on all destinations must be at least as new as the one
used to generate the batch file.  Rsync will die with an error if the protocol
version in the batch file is too new for the batch-reading rsync to handle.
See also the `--protocol` option for a way to have the creating rsync generate
a batch file that an older rsync can understand.  (Note that batch files
changed format in version 2.6.3, so mixing versions older than that with newer
versions will not work.)

When reading a batch file, rsync will force the value of certain options to
match the data in the batch file if you didn't set them to the same as the
batch-writing command.  Other options can (and should) be changed.  For
instance `--write-batch` changes to `--read-batch`, `--files-from` is dropped,
and the `--filter` / `--include` / `--exclude` options are not needed unless
one of the `--delete` options is specified.

The code that creates the BATCH.sh file transforms any filter/include/exclude
options into a single list that is appended as a "here" document to the shell
script file.  An advanced user can use this to modify the exclude list if a
change in what gets deleted by `--delete` is desired.  A normal user can ignore
this detail and just use the shell script as an easy way to run the appropriate
`--read-batch` command for the batched data.

The original batch mode in rsync was based on "rsync+", but the latest
version uses a new implementation.

# SYMBOLIC LINKS

Three basic behaviors are possible when rsync encounters a symbolic
link in the source directory.

By default, symbolic links are not transferred at all.  A message "skipping
non-regular" file is emitted for any symlinks that exist.

If `--links` is specified, then symlinks are recreated with the same target on
the destination.  Note that `--archive` implies `--links`.

If `--copy-links` is specified, then symlinks are "collapsed" by
copying their referent, rather than the symlink.

Rsync can also distinguish "safe" and "unsafe" symbolic links.  An example
where this might be used is a web site mirror that wishes to ensure that the
rsync module that is copied does not include symbolic links to `/etc/passwd` in
the public section of the site.  Using `--copy-unsafe-links` will cause any
links to be copied as the file they point to on the destination.  Using
`--safe-links` will cause unsafe links to be omitted altogether. (Note that you
must specify `--links` for `--safe-links` to have any effect.)

Symbolic links are considered unsafe if they are absolute symlinks
(start with `/`), empty, or if they contain enough ".."
components to ascend from the directory being copied.

Here's a summary of how the symlink options are interpreted.  The list is in
order of precedence, so if your combination of options isn't mentioned, use the
first line that is a complete subset of your options:

0.  `--copy-links` Turn all symlinks into normal files (leaving no symlinks for
    any other options to affect).
0.  `--links --copy-unsafe-links` Turn all unsafe symlinks into files and
    duplicate all safe symlinks.
0.  `--copy-unsafe-links` Turn all unsafe symlinks into files, noisily skip all
    safe symlinks.
0.  `--links --safe-links` Duplicate safe symlinks and skip unsafe ones.
0.  `--links` Duplicate all symlinks.

# DIAGNOSTICS

rsync occasionally produces error messages that may seem a little cryptic.  The
one that seems to cause the most confusion is "protocol version mismatch -- is
your shell clean?".

This message is usually caused by your startup scripts or remote shell facility
producing unwanted garbage on the stream that rsync is using for its transport.
The way to diagnose this problem is to run your remote shell like this:

>     ssh remotehost /bin/true > out.dat

then look at out.dat.  If everything is working correctly then out.dat should
be a zero length file.  If you are getting the above error from rsync then you
will probably find that out.dat contains some text or data.  Look at the
contents and try to work out what is producing it.  The most common cause is
incorrectly configured shell startup scripts (such as .cshrc or .profile) that
contain output statements for non-interactive logins.

If you are having trouble debugging filter patterns, then try specifying the
`-vv` option.  At this level of verbosity rsync will show why each individual
file is included or excluded.

# EXIT VALUES

0.  **0** Success
0.  **1** Syntax or usage error
0.  **2** Protocol incompatibility
0.  **3** Errors selecting input/output files, dirs
0.  **4** Requested action not supported: an attempt was made to manipulate
    64-bit files on a platform that cannot support them; or an option was
    specified that is supported by the client and not by the server.
0.  **5** Error starting client-server protocol
0.  **6** Daemon unable to append to log-file
0.  **10** Error in socket I/O
0.  **11** Error in file I/O
0.  **12** Error in rsync protocol data stream
0.  **13** Errors with program diagnostics
0.  **14** Error in IPC code
0.  **20** Received SIGUSR1 or SIGINT
0.  **21** Some error returned by **waitpid()**
0.  **22** Error allocating core memory buffers
0.  **23** Partial transfer due to error
0.  **24** Partial transfer due to vanished source files
0.  **25** The --max-delete limit stopped deletions
0.  **30** Timeout in data send/receive
0.  **35** Timeout waiting for daemon connection

# ENVIRONMENT VARIABLES

0.  `CVSIGNORE`

    The CVSIGNORE environment variable supplements any ignore patterns in
    .cvsignore files.  See the `--cvs-exclude` option for more details.

0.  `RSYNC_ICONV`

    Specify a default `--iconv` setting using this environment variable. (First
    supported in 3.0.0.)

0.  `RSYNC_PROTECT_ARGS`

    Specify a non-zero numeric value if you want the `--protect-args` option to
    be enabled by default, or a zero value to make sure that it is disabled by
    default. (First supported in 3.1.0.)

0.  `RSYNC_RSH`

    The RSYNC_RSH environment variable allows you to override the default shell
    used as the transport for rsync.  Command line options are permitted after
    the command name, just as in the `-e` option.

0.  `RSYNC_PROXY`

    The RSYNC_PROXY environment variable allows you to redirect your rsync
    client to use a web proxy when connecting to a rsync daemon.  You should
    set RSYNC_PROXY to a hostname:port pair.

0.  `RSYNC_PASSWORD`

    Setting RSYNC_PASSWORD to the required password allows you to run
    authenticated rsync connections to an rsync daemon without user
    intervention.  Note that this does not supply a password to a remote shell
    transport such as ssh; to learn how to do that, consult the remote shell's
    documentation.

0.  `USER` or `LOGNAME`

    The USER or LOGNAME environment variables are used to determine the default
    username sent to an rsync daemon.  If neither is set, the username defaults
    to "nobody".

0.  `HOME`

    The HOME environment variable is used to find the user's default .cvsignore
    file.

# FILES

/etc/rsyncd.conf or rsyncd.conf

# SEE ALSO

**rsync-ssl**(1), **rsyncd.conf**(5)

# BUGS

times are transferred as \*nix time_t values

When transferring to FAT filesystems rsync may re-sync
unmodified files.
See the comments on the `--modify-window` option.

file permissions, devices, etc. are transferred as native numerical
values

see also the comments on the `--delete` option

Please report bugs! See the web site at <https://rsync.samba.org/>.

# VERSION

This man page is current for version @VERSION@ of rsync.

# INTERNAL OPTIONS

The options `--server` and `--sender` are used internally by rsync, and should
never be typed by a user under normal circumstances.  Some awareness of these
options may be needed in certain scenarios, such as when setting up a login
that can only run an rsync command.  For instance, the support directory of the
rsync distribution has an example script named rrsync (for restricted rsync)
that can be used with a restricted ssh login.

# CREDITS

rsync is distributed under the GNU General Public License.  See the file
COPYING for details.

A web site is available at <https://rsync.samba.org/>.  The site includes an
FAQ-O-Matic which may cover questions unanswered by this manual page.

We would be delighted to hear from you if you like this program.  Please
contact the mailing-list at <rsync@lists.samba.org>.

This program uses the excellent zlib compression library written by Jean-loup
Gailly and Mark Adler.

# THANKS

Special thanks go out to: John Van Essen, Matt McCutchen, Wesley W. Terpstra,
David Dykstra, Jos Backus, Sebastian Krahmer, Martin Pool, and our
gone-but-not-forgotten compadre, J.W. Schultz.

Thanks also to Richard Brent, Brendan Mackay, Bill Waite, Stephen Rothwell and
David Bell.  I've probably missed some people, my apologies if I have.

# AUTHOR

rsync was originally written by Andrew Tridgell and Paul Mackerras.  Many
people have later contributed to it. It is currently maintained by Wayne
Davison.

Mailing lists for support and development are available at
<https://lists.samba.org/>.