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1 The CIFS VFS support for Linux supports many advanced network filesystem
2 features such as hierarchical dfs like namespace, hardlinks, locking and more.
3 It was designed to comply with the SNIA CIFS Technical Reference (which
4 supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
5 practical interoperability with Windows 2000, Windows XP, Samba and equivalent
6 servers.
8 For questions or bug reports please contact:
9 sfrench@samba.org (sfrench@us.ibm.com)
11 Build instructions:
12 ==================
13 For Linux 2.4:
14 1) Get the kernel source (e.g.from http://www.kernel.org)
15 and download the cifs vfs source (see the project page
16 at http://us1.samba.org/samba/Linux_CIFS_client.html)
17 and change directory into the top of the kernel directory
18 then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
19 to add the cifs vfs to your kernel configure options if
20 it has not already been added (e.g. current SuSE and UL
21 users do not need to apply the cifs_24.patch since the cifs vfs is
22 already in the kernel configure menu) and then
23 mkdir linux/fs/cifs and then copy the current cifs vfs files from
24 the cifs download to your kernel build directory e.g.
26 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
28 2) make menuconfig (or make xconfig)
29 3) select cifs from within the network filesystem choices
30 4) save and exit
31 5) make dep
32 6) make modules (or "make" if CIFS VFS not to be built as a module)
34 For Linux 2.6:
35 1) Download the kernel (e.g. from http://www.kernel.org)
36 and change directory into the top of the kernel directory tree
37 (e.g. /usr/src/linux-2.5.73)
38 2) make menuconfig (or make xconfig)
39 3) select cifs from within the network filesystem choices
40 4) save and exit
41 5) make
44 Installation instructions:
45 =========================
46 If you have built the CIFS vfs as module (successfully) simply
47 type "make modules_install" (or if you prefer, manually copy the file to
48 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
50 If you have built the CIFS vfs into the kernel itself, follow the instructions
51 for your distribution on how to install a new kernel (usually you
52 would simply type "make install").
54 If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
55 the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
56 similar files reside (usually /sbin). Although the helper software is not
57 required, mount.cifs is recommended. Eventually the Samba 3.0 utility program
58 "net" may also be helpful since it may someday provide easier mount syntax for
59 users who are used to Windows e.g.
60 net use <mount point> <UNC name or cifs URL>
61 Note that running the Winbind pam/nss module (logon service) on all of your
62 Linux clients is useful in mapping Uids and Gids consistently across the
63 domain to the proper network user. The mount.cifs mount helper can be
64 trivially built from Samba 3.0 or later source e.g. by executing:
66 gcc samba/source/client/mount.cifs.c -o mount.cifs
68 If cifs is built as a module, then the size and number of network buffers
69 and maximum number of simultaneous requests to one server can be configured.
70 Changing these from their defaults is not recommended. By executing modinfo
71 modinfo kernel/fs/cifs/cifs.ko
72 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
73 at module initialization time (by running insmod cifs.ko) can be seen.
75 Allowing User Mounts
76 ====================
77 To permit users to mount and unmount over directories they own is possible
78 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
79 utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
80 umount shares they mount requires
81 1) mount.cifs version 1.4 or later
82 2) an entry for the share in /etc/fstab indicating that a user may
83 unmount it e.g.
84 //server/usersharename /mnt/username cifs user 0 0
86 Note that when the mount.cifs utility is run suid (allowing user mounts),
87 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
88 disallow execution of an suid program mounted on the remote target.
89 When mount is executed as root, nosuid is not passed in by default,
90 and execution of suid programs on the remote target would be enabled
91 by default. This can be changed, as with nfs and other filesystems,
92 by simply specifying "nosuid" among the mount options. For user mounts
93 though to be able to pass the suid flag to mount requires rebuilding
94 mount.cifs with the following flag:
96 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
98 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
99 later source tree in docs/manpages/mount.cifs.8
101 Allowing User Unmounts
102 ======================
103 To permit users to ummount directories that they have user mounted (see above),
104 the utility umount.cifs may be used. It may be invoked directly, or if
105 umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
106 (at least for most versions of the umount utility) for umount of cifs
107 mounts, unless umount is invoked with -i (which will avoid invoking a umount
108 helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
109 as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
110 allow adding entries to a file to the /etc/permissions file to achieve the
111 equivalent suid effect). For this utility to succeed the target path
112 must be a cifs mount, and the uid of the current user must match the uid
113 of the user who mounted the resource.
115 Also note that the customary way of allowing user mounts and unmounts is
116 (instead of using mount.cifs and unmount.cifs as suid) to add a line
117 to the file /etc/fstab for each //server/share you wish to mount, but
118 this can become unwieldy when potential mount targets include many
119 or unpredictable UNC names.
121 Samba Considerations
122 ====================
123 To get the maximum benefit from the CIFS VFS, we recommend using a server that
124 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
125 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
126 Note that uid, gid and file permissions will display default values if you do
127 not have a server that supports the Unix extensions for CIFS (such as Samba
128 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
129 the line:
131 unix extensions = yes
133 to your smb.conf file on the server. Note that the following smb.conf settings
134 are also useful (on the Samba server) when the majority of clients are Unix or
135 Linux:
137 case sensitive = yes
138 delete readonly = yes
139 ea support = yes
141 Note that server ea support is required for supporting xattrs from the Linux
142 cifs client, and that EA support is present in later versions of Samba (e.g.
143 3.0.6 and later (also EA support works in all versions of Windows, at least to
144 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
145 feature of most Linux filesystems which may require enabling via
146 make menuconfig. Client support for extended attributes (user xattr) can be
147 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
149 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
150 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
151 then POSIX support in the CIFS configuration options when building the cifs
152 module. POSIX ACL support can be disabled on a per mount basic by specifying
153 "noacl" on mount.
155 Some administrators may want to change Samba's smb.conf "map archive" and
156 "create mask" parameters from the default. Unless the create mask is changed
157 newly created files can end up with an unnecessarily restrictive default mode,
158 which may not be what you want, although if the CIFS Unix extensions are
159 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
160 fix the mode. Note that creating special devices (mknod) remotely
161 may require specifying a mkdev function to Samba if you are not using
162 Samba 3.0.6 or later. For more information on these see the manual pages
163 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
164 unlike the smbfs vfs, does not read the smb.conf on the client system
165 (the few optional settings are passed in on mount via -o parameters instead).
166 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
167 open files (required for strict POSIX compliance). Windows Servers already
168 supported this feature. Samba server does not allow symlinks that refer to files
169 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
170 files with absolute paths (ie beginning with slash) such as:
171 ln -s /mnt/foo bar
172 would be forbidden. Samba 3.0.6 server or later includes the ability to create
173 such symlinks safely by converting unsafe symlinks (ie symlinks to server
174 files that are outside of the share) to a samba specific format on the server
175 that is ignored by local server applications and non-cifs clients and that will
176 not be traversed by the Samba server). This is opaque to the Linux client
177 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
178 later, but only for remote clients using the CIFS Unix extensions, and will
179 be invisbile to Windows clients and typically will not affect local
180 applications running on the same server as Samba.
182 Use instructions:
183 ================
184 Once the CIFS VFS support is built into the kernel or installed as a module
185 (cifs.o), you can use mount syntax like the following to access Samba or Windows
186 servers:
188 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
190 Before -o the option -v may be specified to make the mount.cifs
191 mount helper display the mount steps more verbosely.
192 After -o the following commonly used cifs vfs specific options
193 are supported:
195 user=<username>
196 pass=<password>
197 domain=<domain name>
199 Other cifs mount options are described below. Use of TCP names (in addition to
200 ip addresses) is available if the mount helper (mount.cifs) is installed. If
201 you do not trust the server to which are mounted, or if you do not have
202 cifs signing enabled (and the physical network is insecure), consider use
203 of the standard mount options "noexec" and "nosuid" to reduce the risk of
204 running an altered binary on your local system (downloaded from a hostile server
205 or altered by a hostile router).
207 Although mounting using format corresponding to the CIFS URL specification is
208 not possible in mount.cifs yet, it is possible to use an alternate format
209 for the server and sharename (which is somewhat similar to NFS style mount
210 syntax) instead of the more widely used UNC format (i.e. \\server\share):
211 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
213 When using the mount helper mount.cifs, passwords may be specified via alternate
214 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
215 on the command line:
216 1) By including it in a credential file. Specify credentials=filename as one
217 of the mount options. Credential files contain two lines
218 username=someuser
219 password=your_password
220 2) By specifying the password in the PASSWD environment variable (similarly
221 the user name can be taken from the USER environment variable).
222 3) By specifying the password in a file by name via PASSWD_FILE
223 4) By specifying the password in a file by file descriptor via PASSWD_FD
225 If no password is provided, mount.cifs will prompt for password entry
227 Restrictions
228 ============
229 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
230 1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
231 problem as most servers support this.
233 Valid filenames differ between Windows and Linux. Windows typically restricts
234 filenames which contain certain reserved characters (e.g.the character :
235 which is used to delimit the beginning of a stream name by Windows), while
236 Linux allows a slightly wider set of valid characters in filenames. Windows
237 servers can remap such characters when an explicit mapping is specified in
238 the Server's registry. Samba starting with version 3.10 will allow such
239 filenames (ie those which contain valid Linux characters, which normally
240 would be forbidden for Windows/CIFS semantics) as long as the server is
241 configured for Unix Extensions (and the client has not disabled
242 /proc/fs/cifs/LinuxExtensionsEnabled).
245 CIFS VFS Mount Options
246 ======================
247 A partial list of the supported mount options follows:
248 user The user name to use when trying to establish
249 the CIFS session.
250 password The user password. If the mount helper is
251 installed, the user will be prompted for password
252 if not supplied.
253 ip The ip address of the target server
254 unc The target server Universal Network Name (export) to
255 mount.
256 domain Set the SMB/CIFS workgroup name prepended to the
257 username during CIFS session establishment
258 uid Set the default uid for inodes. For mounts to servers
259 which do support the CIFS Unix extensions, such as a
260 properly configured Samba server, the server provides
261 the uid, gid and mode so this parameter should not be
262 specified unless the server and clients uid and gid
263 numbering differ. If the server and client are in the
264 same domain (e.g. running winbind or nss_ldap) and
265 the server supports the Unix Extensions then the uid
266 and gid can be retrieved from the server (and uid
267 and gid would not have to be specifed on the mount.
268 For servers which do not support the CIFS Unix
269 extensions, the default uid (and gid) returned on lookup
270 of existing files will be the uid (gid) of the person
271 who executed the mount (root, except when mount.cifs
272 is configured setuid for user mounts) unless the "uid="
273 (gid) mount option is specified. For the uid (gid) of newly
274 created files and directories, ie files created since
275 the last mount of the server share, the expected uid
276 (gid) is cached as long as the inode remains in
277 memory on the client. Also note that permission
278 checks (authorization checks) on accesses to a file occur
279 at the server, but there are cases in which an administrator
280 may want to restrict at the client as well. For those
281 servers which do not report a uid/gid owner
282 (such as Windows), permissions can also be checked at the
283 client, and a crude form of client side permission checking
284 can be enabled by specifying file_mode and dir_mode on
285 the client. Note that the mount.cifs helper must be
286 at version 1.10 or higher to support specifying the uid
287 (or gid) in non-numeric form.
288 gid Set the default gid for inodes (similar to above).
289 file_mode If CIFS Unix extensions are not supported by the server
290 this overrides the default mode for file inodes.
291 dir_mode If CIFS Unix extensions are not supported by the server
292 this overrides the default mode for directory inodes.
293 port attempt to contact the server on this tcp port, before
294 trying the usual ports (port 445, then 139).
295 iocharset Codepage used to convert local path names to and from
296 Unicode. Unicode is used by default for network path
297 names if the server supports it. If iocharset is
298 not specified then the nls_default specified
299 during the local client kernel build will be used.
300 If server does not support Unicode, this parameter is
301 unused.
302 rsize default read size (usually 16K). The client currently
303 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
304 defaults to 16K and may be changed (from 8K to the maximum
305 kmalloc size allowed by your kernel) at module install time
306 for cifs.ko. Setting CIFSMaxBufSize to a very large value
307 will cause cifs to use more memory and may reduce performance
308 in some cases. To use rsize greater than 127K (the original
309 cifs protocol maximum) also requires that the server support
310 a new Unix Capability flag (for very large read) which some
311 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
312 set from a minimum of 2048 to a maximum of 130048 (127K or
313 CIFSMaxBufSize, whichever is smaller)
314 wsize default write size (default 57344)
315 maximum wsize currently allowed by CIFS is 57344 (fourteen
316 4096 byte pages)
317 rw mount the network share read-write (note that the
318 server may still consider the share read-only)
319 ro mount network share read-only
320 version used to distinguish different versions of the
321 mount helper utility (not typically needed)
322 sep if first mount option (after the -o), overrides
323 the comma as the separator between the mount
324 parms. e.g.
325 -o user=myname,password=mypassword,domain=mydom
326 could be passed instead with period as the separator by
327 -o sep=.user=myname.password=mypassword.domain=mydom
328 this might be useful when comma is contained within username
329 or password or domain. This option is less important
330 when the cifs mount helper cifs.mount (version 1.1 or later)
331 is used.
332 nosuid Do not allow remote executables with the suid bit
333 program to be executed. This is only meaningful for mounts
334 to servers such as Samba which support the CIFS Unix Extensions.
335 If you do not trust the servers in your network (your mount
336 targets) it is recommended that you specify this option for
337 greater security.
338 exec Permit execution of binaries on the mount.
339 noexec Do not permit execution of binaries on the mount.
340 dev Recognize block devices on the remote mount.
341 nodev Do not recognize devices on the remote mount.
342 suid Allow remote files on this mountpoint with suid enabled to
343 be executed (default for mounts when executed as root,
344 nosuid is default for user mounts).
345 credentials Although ignored by the cifs kernel component, it is used by
346 the mount helper, mount.cifs. When mount.cifs is installed it
347 opens and reads the credential file specified in order
348 to obtain the userid and password arguments which are passed to
349 the cifs vfs.
350 guest Although ignored by the kernel component, the mount.cifs
351 mount helper will not prompt the user for a password
352 if guest is specified on the mount options. If no
353 password is specified a null password will be used.
354 perm Client does permission checks (vfs_permission check of uid
355 and gid of the file against the mode and desired operation),
356 Note that this is in addition to the normal ACL check on the
357 target machine done by the server software.
358 Client permission checking is enabled by default.
359 noperm Client does not do permission checks. This can expose
360 files on this mount to access by other users on the local
361 client system. It is typically only needed when the server
362 supports the CIFS Unix Extensions but the UIDs/GIDs on the
363 client and server system do not match closely enough to allow
364 access by the user doing the mount, but it may be useful with
365 non CIFS Unix Extension mounts for cases in which the default
366 mode is specified on the mount but is not to be enforced on the
367 client (e.g. perhaps when MultiUserMount is enabled)
368 Note that this does not affect the normal ACL check on the
369 target machine done by the server software (of the server
370 ACL against the user name provided at mount time).
371 serverino Use server's inode numbers instead of generating automatically
372 incrementing inode numbers on the client. Although this will
373 make it easier to spot hardlinked files (as they will have
374 the same inode numbers) and inode numbers may be persistent,
375 note that the server does not guarantee that the inode numbers
376 are unique if multiple server side mounts are exported under a
377 single share (since inode numbers on the servers might not
378 be unique if multiple filesystems are mounted under the same
379 shared higher level directory). Note that some older
380 (e.g. pre-Windows 2000) do not support returning UniqueIDs
381 or the CIFS Unix Extensions equivalent and for those
382 this mount option will have no effect. Exporting cifs mounts
383 under nfsd requires this mount option on the cifs mount.
384 noserverino Client generates inode numbers (rather than using the actual one
385 from the server) by default.
386 setuids If the CIFS Unix extensions are negotiated with the server
387 the client will attempt to set the effective uid and gid of
388 the local process on newly created files, directories, and
389 devices (create, mkdir, mknod). If the CIFS Unix Extensions
390 are not negotiated, for newly created files and directories
391 instead of using the default uid and gid specified on
392 the mount, cache the new file's uid and gid locally which means
393 that the uid for the file can change when the inode is
394 reloaded (or the user remounts the share).
395 nosetuids The client will not attempt to set the uid and gid on
396 on newly created files, directories, and devices (create,
397 mkdir, mknod) which will result in the server setting the
398 uid and gid to the default (usually the server uid of the
399 user who mounted the share). Letting the server (rather than
400 the client) set the uid and gid is the default. If the CIFS
401 Unix Extensions are not negotiated then the uid and gid for
402 new files will appear to be the uid (gid) of the mounter or the
403 uid (gid) parameter specified on the mount.
404 netbiosname When mounting to servers via port 139, specifies the RFC1001
405 source name to use to represent the client netbios machine
406 name when doing the RFC1001 netbios session initialize.
407 direct Do not do inode data caching on files opened on this mount.
408 This precludes mmaping files on this mount. In some cases
409 with fast networks and little or no caching benefits on the
410 client (e.g. when the application is doing large sequential
411 reads bigger than page size without rereading the same data)
412 this can provide better performance than the default
413 behavior which caches reads (readahead) and writes
414 (writebehind) through the local Linux client pagecache
415 if oplock (caching token) is granted and held. Note that
416 direct allows write operations larger than page size
417 to be sent to the server.
418 acl Allow setfacl and getfacl to manage posix ACLs if server
419 supports them. (default)
420 noacl Do not allow setfacl and getfacl calls on this mount
421 user_xattr Allow getting and setting user xattrs (those attributes whose
422 name begins with "user." or "os2.") as OS/2 EAs (extended
423 attributes) to the server. This allows support of the
424 setfattr and getfattr utilities. (default)
425 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
426 mapchars Translate six of the seven reserved characters (not backslash)
427 *?<>|:
428 to the remap range (above 0xF000), which also
429 allows the CIFS client to recognize files created with
430 such characters by Windows's POSIX emulation. This can
431 also be useful when mounting to most versions of Samba
432 (which also forbids creating and opening files
433 whose names contain any of these seven characters).
434 This has no effect if the server does not support
435 Unicode on the wire.
436 nomapchars Do not translate any of these seven characters (default).
437 nocase Request case insensitive path name matching (case
438 sensitive is the default if the server suports it).
439 (mount option "ignorecase" is identical to "nocase")
440 posixpaths If CIFS Unix extensions are supported, attempt to
441 negotiate posix path name support which allows certain
442 characters forbidden in typical CIFS filenames, without
443 requiring remapping. (default)
444 noposixpaths If CIFS Unix extensions are supported, do not request
445 posix path name support (this may cause servers to
446 reject creatingfile with certain reserved characters).
447 nounix Disable the CIFS Unix Extensions for this mount (tree
448 connection). This is rarely needed, but it may be useful
449 in order to turn off multiple settings all at once (ie
450 posix acls, posix locks, posix paths, symlink support
451 and retrieving uids/gids/mode from the server) or to
452 work around a bug in server which implement the Unix
453 Extensions.
454 nobrl Do not send byte range lock requests to the server.
455 This is necessary for certain applications that break
456 with cifs style mandatory byte range locks (and most
457 cifs servers do not yet support requesting advisory
458 byte range locks).
459 remount remount the share (often used to change from ro to rw mounts
460 or vice versa)
461 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
462 the file. (EXPERIMENTAL)
463 servern Specify the server 's netbios name (RFC1001 name) to use
464 when attempting to setup a session to the server. This is
465 This is needed for mounting to some older servers (such
466 as OS/2 or Windows 98 and Windows ME) since they do not
467 support a default server name. A server name can be up
468 to 15 characters long and is usually uppercased.
469 sfu When the CIFS Unix Extensions are not negotiated, attempt to
470 create device files and fifos in a format compatible with
471 Services for Unix (SFU). In addition retrieve bits 10-12
472 of the mode via the SETFILEBITS extended attribute (as
473 SFU does). In the future the bottom 9 bits of the
474 mode also will be emulated using queries of the security
475 descriptor (ACL).
476 sign Must use packet signing (helps avoid unwanted data modification
477 by intermediate systems in the route). Note that signing
478 does not work with lanman or plaintext authentication.
479 sec Security mode. Allowed values are:
480 none attempt to connection as a null user (no name)
481 krb5 Use Kerberos version 5 authentication
482 krb5i Use Kerberos authentication and packet signing
483 ntlm Use NTLM password hashing (default)
484 ntlmi Use NTLM password hashing with signing (if
485 /proc/fs/cifs/PacketSigningEnabled on or if
486 server requires signing also can be the default)
487 ntlmv2 Use NTLMv2 password hashing
488 ntlmv2i Use NTLMv2 password hashing with packet signing
489 lanman (if configured in kernel config) use older
490 lanman hash
491 hard Retry file operations if server is not responding
492 soft Limit retries to unresponsive servers (usually only
493 one retry) before returning an error. (default)
495 The mount.cifs mount helper also accepts a few mount options before -o
496 including:
498 -S take password from stdin (equivalent to setting the environment
499 variable "PASSWD_FD=0"
500 -V print mount.cifs version
501 -? display simple usage information
503 With most 2.6 kernel versions of modutils, the version of the cifs kernel
504 module can be displayed via modinfo.
506 Misc /proc/fs/cifs Flags and Debug Info
507 =======================================
508 Informational pseudo-files:
509 DebugData Displays information about active CIFS sessions
510 and shares, as well as the cifs.ko version.
511 Stats Lists summary resource usage information as well as per
512 share statistics, if CONFIG_CIFS_STATS in enabled
513 in the kernel configuration.
515 Configuration pseudo-files:
516 MultiuserMount If set to one, more than one CIFS session to
517 the same server ip address can be established
518 if more than one uid accesses the same mount
519 point and if the uids user/password mapping
520 information is available. (default is 0)
521 PacketSigningEnabled If set to one, cifs packet signing is enabled
522 and will be used if the server requires
523 it. If set to two, cifs packet signing is
524 required even if the server considers packet
525 signing optional. (default 1)
526 SecurityFlags Flags which control security negotiation and
527 also packet signing. Authentication (may/must)
528 flags (e.g. for NTLM and/or NTLMv2) may be combined with
529 the signing flags. Specifying two different password
530 hashing mechanisms (as "must use") on the other hand
531 does not make much sense. Default flags are
532 0x07007
533 (NTLM, NTLMv2 and packet signing allowed). Maximum
534 allowable flags if you want to allow mounts to servers
535 using weaker password hashes is 0x37037 (lanman,
536 plaintext, ntlm, ntlmv2, signing allowed):
538 may use packet signing 0x00001
539 must use packet signing 0x01001
540 may use NTLM (most common password hash) 0x00002
541 must use NTLM 0x02002
542 may use NTLMv2 0x00004
543 must use NTLMv2 0x04004
544 may use Kerberos security 0x00008
545 must use Kerberos 0x08008
546 may use lanman (weak) password hash 0x00010
547 must use lanman password hash 0x10010
548 may use plaintext passwords 0x00020
549 must use plaintext passwords 0x20020
550 (reserved for future packet encryption) 0x00040
552 cifsFYI If set to non-zero value, additional debug information
553 will be logged to the system error log. This field
554 contains three flags controlling different classes of
555 debugging entries. The maximum value it can be set
556 to is 7 which enables all debugging points (default 0).
557 Some debugging statements are not compiled into the
558 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
559 kernel configuration. cifsFYI may be set to one or
560 nore of the following flags (7 sets them all):
562 log cifs informational messages 0x01
563 log return codes from cifs entry points 0x02
564 log slow responses (ie which take longer than 1 second)
565 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
568 traceSMB If set to one, debug information is logged to the
569 system error log with the start of smb requests
570 and responses (default 0)
571 LookupCacheEnable If set to one, inode information is kept cached
572 for one second improving performance of lookups
573 (default 1)
574 OplockEnabled If set to one, safe distributed caching enabled.
575 (default 1)
576 LinuxExtensionsEnabled If set to one then the client will attempt to
577 use the CIFS "UNIX" extensions which are optional
578 protocol enhancements that allow CIFS servers
579 to return accurate UID/GID information as well
580 as support symbolic links. If you use servers
581 such as Samba that support the CIFS Unix
582 extensions but do not want to use symbolic link
583 support and want to map the uid and gid fields
584 to values supplied at mount (rather than the
585 actual values, then set this to zero. (default 1)
586 Experimental When set to 1 used to enable certain experimental
587 features (currently enables multipage writes
588 when signing is enabled, the multipage write
589 performance enhancement was disabled when
590 signing turned on in case buffer was modified
591 just before it was sent, also this flag will
592 be used to use the new experimental directory change
593 notification code).
595 These experimental features and tracing can be enabled by changing flags in
596 /proc/fs/cifs (after the cifs module has been installed or built into the
597 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
598 tracing to the kernel message log type:
600 echo 7 > /proc/fs/cifs/cifsFYI
602 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
603 logging of various informational messages. 2 enables logging of non-zero
604 SMB return codes while 4 enables logging of requests that take longer
605 than one second to complete (except for byte range lock requests).
606 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
607 source code (typically by setting it in the beginning of cifsglob.h),
608 and setting it to seven enables all three. Finally, tracing
609 the start of smb requests and responses can be enabled via:
611 echo 1 > /proc/fs/cifs/traceSMB
613 Two other experimental features are under development. To test these
614 requires enabling CONFIG_CIFS_EXPERIMENTAL
616 cifsacl support needed to retrieve approximated mode bits based on
617 the contents on the CIFS ACL.
619 DNOTIFY fcntl: needed for support of directory change
620 notification and perhaps later for file leases)
622 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
623 if the kernel was configured with cifs statistics enabled. The statistics
624 represent the number of successful (ie non-zero return code from the server)
625 SMB responses to some of the more common commands (open, delete, mkdir etc.).
626 Also recorded is the total bytes read and bytes written to the server for
627 that share. Note that due to client caching effects this can be less than the
628 number of bytes read and written by the application running on the client.
629 The statistics for the number of total SMBs and oplock breaks are different in
630 that they represent all for that share, not just those for which the server
631 returned success.
633 Also note that "cat /proc/fs/cifs/DebugData" will display information about
634 the active sessions and the shares that are mounted.
635 Enabling Kerberos (extended security) works when CONFIG_CIFS_EXPERIMENTAL is
636 on but requires a user space helper (from the Samba project). NTLM and NTLMv2 and
637 LANMAN support do not require this helper.