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1 The Linux NTFS filesystem driver
2 ================================
5 Table of contents
6 =================
8 - Overview
9 - Web site
10 - Features
11 - Supported mount options
12 - Known bugs and (mis-)features
13 - Using NTFS volume and stripe sets
14 - The Device-Mapper driver
15 - The Software RAID / MD driver
16 - Limitations when using the MD driver
19 Overview
20 ========
22 Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
23 These include mkntfs, a full-featured ntfs filesystem format utility,
24 ntfsundelete used for recovering files that were unintentionally deleted
25 from an NTFS volume and ntfsresize which is used to resize an NTFS partition.
26 See the web site for more information.
28 To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file
29 system type 'ntfs'. The driver currently supports read-only mode (with no
30 fault-tolerance, encryption or journalling) and very limited, but safe, write
31 support.
33 For fault tolerance and raid support (i.e. volume and stripe sets), you can
34 use the kernel's Software RAID / MD driver. See section "Using Software RAID
35 with NTFS" for details.
38 Web site
39 ========
41 There is plenty of additional information on the linux-ntfs web site
42 at http://www.linux-ntfs.org/
44 The web site has a lot of additional information, such as a comprehensive
45 FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS
46 userspace utilities, etc.
49 Features
50 ========
52 - This is a complete rewrite of the NTFS driver that used to be in the 2.4 and
53 earlier kernels. This new driver implements NTFS read support and is
54 functionally equivalent to the old ntfs driver and it also implements limited
55 write support. The biggest limitation at present is that files/directories
56 cannot be created or deleted. See below for the list of write features that
57 are so far supported. Another limitation is that writing to compressed files
58 is not implemented at all. Also, neither read nor write access to encrypted
59 files is so far implemented.
60 - The new driver has full support for sparse files on NTFS 3.x volumes which
61 the old driver isn't happy with.
62 - The new driver supports execution of binaries due to mmap() now being
63 supported.
64 - The new driver supports loopback mounting of files on NTFS which is used by
65 some Linux distributions to enable the user to run Linux from an NTFS
66 partition by creating a large file while in Windows and then loopback
67 mounting the file while in Linux and creating a Linux filesystem on it that
68 is used to install Linux on it.
69 - A comparison of the two drivers using:
70 time find . -type f -exec md5sum "{}" \;
71 run three times in sequence with each driver (after a reboot) on a 1.4GiB
72 NTFS partition, showed the new driver to be 20% faster in total time elapsed
73 (from 9:43 minutes on average down to 7:53). The time spent in user space
74 was unchanged but the time spent in the kernel was decreased by a factor of
75 2.5 (from 85 CPU seconds down to 33).
76 - The driver does not support short file names in general. For backwards
77 compatibility, we implement access to files using their short file names if
78 they exist. The driver will not create short file names however, and a
79 rename will discard any existing short file name.
80 - The new driver supports exporting of mounted NTFS volumes via NFS.
81 - The new driver supports async io (aio).
82 - The new driver supports fsync(2), fdatasync(2), and msync(2).
83 - The new driver supports readv(2) and writev(2).
84 - The new driver supports access time updates (including mtime and ctime).
85 - The new driver supports truncate(2) and open(2) with O_TRUNC. But at present
86 only very limited support for highly fragmented files, i.e. ones which have
87 their data attribute split across multiple extents, is included. Another
88 limitation is that at present truncate(2) will never create sparse files,
89 since to mark a file sparse we need to modify the directory entry for the
90 file and we do not implement directory modifications yet.
91 - The new driver supports write(2) which can both overwrite existing data and
92 extend the file size so that you can write beyond the existing data. Also,
93 writing into sparse regions is supported and the holes are filled in with
94 clusters. But at present only limited support for highly fragmented files,
95 i.e. ones which have their data attribute split across multiple extents, is
96 included. Another limitation is that write(2) will never create sparse
97 files, since to mark a file sparse we need to modify the directory entry for
98 the file and we do not implement directory modifications yet.
100 Supported mount options
101 =======================
103 In addition to the generic mount options described by the manual page for the
104 mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the
105 following mount options:
107 iocharset=name Deprecated option. Still supported but please use
108 nls=name in the future. See description for nls=name.
110 nls=name Character set to use when returning file names.
111 Unlike VFAT, NTFS suppresses names that contain
112 unconvertible characters. Note that most character
113 sets contain insufficient characters to represent all
114 possible Unicode characters that can exist on NTFS.
115 To be sure you are not missing any files, you are
116 advised to use nls=utf8 which is capable of
117 representing all Unicode characters.
119 utf8=<bool> Option no longer supported. Currently mapped to
120 nls=utf8 but please use nls=utf8 in the future and
121 make sure utf8 is compiled either as module or into
122 the kernel. See description for nls=name.
124 uid=
125 gid=
126 umask= Provide default owner, group, and access mode mask.
127 These options work as documented in mount(8). By
128 default, the files/directories are owned by root and
129 he/she has read and write permissions, as well as
130 browse permission for directories. No one else has any
131 access permissions. I.e. the mode on all files is by
132 default rw------- and for directories rwx------, a
133 consequence of the default fmask=0177 and dmask=0077.
134 Using a umask of zero will grant all permissions to
135 everyone, i.e. all files and directories will have mode
136 rwxrwxrwx.
138 fmask=
139 dmask= Instead of specifying umask which applies both to
140 files and directories, fmask applies only to files and
141 dmask only to directories.
143 sloppy=<BOOL> If sloppy is specified, ignore unknown mount options.
144 Otherwise the default behaviour is to abort mount if
145 any unknown options are found.
147 show_sys_files=<BOOL> If show_sys_files is specified, show the system files
148 in directory listings. Otherwise the default behaviour
149 is to hide the system files.
150 Note that even when show_sys_files is specified, "$MFT"
151 will not be visible due to bugs/mis-features in glibc.
152 Further, note that irrespective of show_sys_files, all
153 files are accessible by name, i.e. you can always do
154 "ls -l \$UpCase" for example to specifically show the
155 system file containing the Unicode upcase table.
157 case_sensitive=<BOOL> If case_sensitive is specified, treat all file names as
158 case sensitive and create file names in the POSIX
159 namespace. Otherwise the default behaviour is to treat
160 file names as case insensitive and to create file names
161 in the WIN32/LONG name space. Note, the Linux NTFS
162 driver will never create short file names and will
163 remove them on rename/delete of the corresponding long
164 file name.
165 Note that files remain accessible via their short file
166 name, if it exists. If case_sensitive, you will need
167 to provide the correct case of the short file name.
169 disable_sparse=<BOOL> If disable_sparse is specified, creation of sparse
170 regions, i.e. holes, inside files is disabled for the
171 volume (for the duration of this mount only). By
172 default, creation of sparse regions is enabled, which
173 is consistent with the behaviour of traditional Unix
174 filesystems.
176 errors=opt What to do when critical filesystem errors are found.
177 Following values can be used for "opt":
178 continue: DEFAULT, try to clean-up as much as
179 possible, e.g. marking a corrupt inode as
180 bad so it is no longer accessed, and then
181 continue.
182 recover: At present only supported is recovery of
183 the boot sector from the backup copy.
184 If read-only mount, the recovery is done
185 in memory only and not written to disk.
186 Note that the options are additive, i.e. specifying:
187 errors=continue,errors=recover
188 means the driver will attempt to recover and if that
189 fails it will clean-up as much as possible and
190 continue.
192 mft_zone_multiplier= Set the MFT zone multiplier for the volume (this
193 setting is not persistent across mounts and can be
194 changed from mount to mount but cannot be changed on
195 remount). Values of 1 to 4 are allowed, 1 being the
196 default. The MFT zone multiplier determines how much
197 space is reserved for the MFT on the volume. If all
198 other space is used up, then the MFT zone will be
199 shrunk dynamically, so this has no impact on the
200 amount of free space. However, it can have an impact
201 on performance by affecting fragmentation of the MFT.
202 In general use the default. If you have a lot of small
203 files then use a higher value. The values have the
204 following meaning:
205 Value MFT zone size (% of volume size)
206 1 12.5%
207 2 25%
208 3 37.5%
209 4 50%
210 Note this option is irrelevant for read-only mounts.
213 Known bugs and (mis-)features
214 =============================
216 - The link count on each directory inode entry is set to 1, due to Linux not
217 supporting directory hard links. This may well confuse some user space
218 applications, since the directory names will have the same inode numbers.
219 This also speeds up ntfs_read_inode() immensely. And we haven't found any
220 problems with this approach so far. If you find a problem with this, please
221 let us know.
224 Please send bug reports/comments/feedback/abuse to the Linux-NTFS development
225 list at sourceforge: linux-ntfs-dev@lists.sourceforge.net
228 Using NTFS volume and stripe sets
229 =================================
231 For support of volume and stripe sets, you can either use the kernel's
232 Device-Mapper driver or the kernel's Software RAID / MD driver. The former is
233 the recommended one to use for linear raid. But the latter is required for
234 raid level 5. For striping and mirroring, either driver should work fine.
237 The Device-Mapper driver
238 ------------------------
240 You will need to create a table of the components of the volume/stripe set and
241 how they fit together and load this into the kernel using the dmsetup utility
242 (see man 8 dmsetup).
244 Linear volume sets, i.e. linear raid, has been tested and works fine. Even
245 though untested, there is no reason why stripe sets, i.e. raid level 0, and
246 mirrors, i.e. raid level 1 should not work, too. Stripes with parity, i.e.
247 raid level 5, unfortunately cannot work yet because the current version of the
248 Device-Mapper driver does not support raid level 5. You may be able to use the
249 Software RAID / MD driver for raid level 5, see the next section for details.
251 To create the table describing your volume you will need to know each of its
252 components and their sizes in sectors, i.e. multiples of 512-byte blocks.
254 For NT4 fault tolerant volumes you can obtain the sizes using fdisk. So for
255 example if one of your partitions is /dev/hda2 you would do:
257 $ fdisk -ul /dev/hda
259 Disk /dev/hda: 81.9 GB, 81964302336 bytes
260 255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors
261 Units = sectors of 1 * 512 = 512 bytes
263 Device Boot Start End Blocks Id System
264 /dev/hda1 * 63 4209029 2104483+ 83 Linux
265 /dev/hda2 4209030 37768814 16779892+ 86 NTFS
266 /dev/hda3 37768815 46170809 4200997+ 83 Linux
268 And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 =
269 33559785 sectors.
271 For Win2k and later dynamic disks, you can for example use the ldminfo utility
272 which is part of the Linux LDM tools (the latest version at the time of
273 writing is linux-ldm-0.0.8.tar.bz2). You can download it from:
274 http://www.linux-ntfs.org/
275 Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go
276 into it (cd linux-ldm-0.0.8) and change to the test directory (cd test). You
277 will find the precompiled (i386) ldminfo utility there. NOTE: You will not be
278 able to compile this yourself easily so use the binary version!
280 Then you would use ldminfo in dump mode to obtain the necessary information:
282 $ ./ldminfo --dump /dev/hda
284 This would dump the LDM database found on /dev/hda which describes all of your
285 dynamic disks and all the volumes on them. At the bottom you will see the
286 VOLUME DEFINITIONS section which is all you really need. You may need to look
287 further above to determine which of the disks in the volume definitions is
288 which device in Linux. Hint: Run ldminfo on each of your dynamic disks and
289 look at the Disk Id close to the top of the output for each (the PRIVATE HEADER
290 section). You can then find these Disk Ids in the VBLK DATABASE section in the
291 <Disk> components where you will get the LDM Name for the disk that is found in
292 the VOLUME DEFINITIONS section.
294 Note you will also need to enable the LDM driver in the Linux kernel. If your
295 distribution did not enable it, you will need to recompile the kernel with it
296 enabled. This will create the LDM partitions on each device at boot time. You
297 would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc)
298 in the Device-Mapper table.
300 You can also bypass using the LDM driver by using the main device (e.g.
301 /dev/hda) and then using the offsets of the LDM partitions into this device as
302 the "Start sector of device" when creating the table. Once again ldminfo would
303 give you the correct information to do this.
305 Assuming you know all your devices and their sizes things are easy.
307 For a linear raid the table would look like this (note all values are in
308 512-byte sectors):
310 --- cut here ---
311 # Offset into Size of this Raid type Device Start sector
312 # volume device of device
313 0 1028161 linear /dev/hda1 0
314 1028161 3903762 linear /dev/hdb2 0
315 4931923 2103211 linear /dev/hdc1 0
316 --- cut here ---
318 For a striped volume, i.e. raid level 0, you will need to know the chunk size
319 you used when creating the volume. Windows uses 64kiB as the default, so it
320 will probably be this unless you changes the defaults when creating the array.
322 For a raid level 0 the table would look like this (note all values are in
323 512-byte sectors):
325 --- cut here ---
326 # Offset Size Raid Number Chunk 1st Start 2nd Start
327 # into of the type of size Device in Device in
328 # volume volume stripes device device
329 0 2056320 striped 2 128 /dev/hda1 0 /dev/hdb1 0
330 --- cut here ---
332 If there are more than two devices, just add each of them to the end of the
333 line.
335 Finally, for a mirrored volume, i.e. raid level 1, the table would look like
336 this (note all values are in 512-byte sectors):
338 --- cut here ---
339 # Ofs Size Raid Log Number Region Should Number Source Start Target Start
340 # in of the type type of log size sync? of Device in Device in
341 # vol volume params mirrors Device Device
342 0 2056320 mirror core 2 16 nosync 2 /dev/hda1 0 /dev/hdb1 0
343 --- cut here ---
345 If you are mirroring to multiple devices you can specify further targets at the
346 end of the line.
348 Note the "Should sync?" parameter "nosync" means that the two mirrors are
349 already in sync which will be the case on a clean shutdown of Windows. If the
350 mirrors are not clean, you can specify the "sync" option instead of "nosync"
351 and the Device-Mapper driver will then copy the entirety of the "Source Device"
352 to the "Target Device" or if you specified multiple target devices to all of
353 them.
355 Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1),
356 and hand it over to dmsetup to work with, like so:
358 $ dmsetup create myvolume1 /etc/ntfsvolume1
360 You can obviously replace "myvolume1" with whatever name you like.
362 If it all worked, you will now have the device /dev/device-mapper/myvolume1
363 which you can then just use as an argument to the mount command as usual to
364 mount the ntfs volume. For example:
366 $ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1
368 (You need to create the directory /mnt/myvol1 first and of course you can use
369 anything you like instead of /mnt/myvol1 as long as it is an existing
370 directory.)
372 It is advisable to do the mount read-only to see if the volume has been setup
373 correctly to avoid the possibility of causing damage to the data on the ntfs
374 volume.
377 The Software RAID / MD driver
378 -----------------------------
380 An alternative to using the Device-Mapper driver is to use the kernel's
381 Software RAID / MD driver. For which you need to set up your /etc/raidtab
382 appropriately (see man 5 raidtab).
384 Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level
385 0, have been tested and work fine (though see section "Limitations when using
386 the MD driver with NTFS volumes" especially if you want to use linear raid).
387 Even though untested, there is no reason why mirrors, i.e. raid level 1, and
388 stripes with parity, i.e. raid level 5, should not work, too.
390 You have to use the "persistent-superblock 0" option for each raid-disk in the
391 NTFS volume/stripe you are configuring in /etc/raidtab as the persistent
392 superblock used by the MD driver would damage the NTFS volume.
394 Windows by default uses a stripe chunk size of 64k, so you probably want the
395 "chunk-size 64k" option for each raid-disk, too.
397 For example, if you have a stripe set consisting of two partitions /dev/hda5
398 and /dev/hdb1 your /etc/raidtab would look like this:
400 raiddev /dev/md0
401 raid-level 0
402 nr-raid-disks 2
403 nr-spare-disks 0
404 persistent-superblock 0
405 chunk-size 64k
406 device /dev/hda5
407 raid-disk 0
408 device /dev/hdb1
409 raid-disk 1
411 For linear raid, just change the raid-level above to "raid-level linear", for
412 mirrors, change it to "raid-level 1", and for stripe sets with parity, change
413 it to "raid-level 5".
415 Note for stripe sets with parity you will also need to tell the MD driver
416 which parity algorithm to use by specifying the option "parity-algorithm
417 which", where you need to replace "which" with the name of the algorithm to
418 use (see man 5 raidtab for available algorithms) and you will have to try the
419 different available algorithms until you find one that works. Make sure you
420 are working read-only when playing with this as you may damage your data
421 otherwise. If you find which algorithm works please let us know (email the
422 linux-ntfs developers list linux-ntfs-dev@lists.sourceforge.net or drop in on
423 IRC in channel #ntfs on the irc.freenode.net network) so we can update this
424 documentation.
426 Once the raidtab is setup, run for example raid0run -a to start all devices or
427 raid0run /dev/md0 to start a particular md device, in this case /dev/md0.
429 Then just use the mount command as usual to mount the ntfs volume using for
430 example: mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume
432 It is advisable to do the mount read-only to see if the md volume has been
433 setup correctly to avoid the possibility of causing damage to the data on the
434 ntfs volume.
437 Limitations when using the Software RAID / MD driver
438 -----------------------------------------------------
440 Using the md driver will not work properly if any of your NTFS partitions have
441 an odd number of sectors. This is especially important for linear raid as all
442 data after the first partition with an odd number of sectors will be offset by
443 one or more sectors so if you mount such a partition with write support you
444 will cause massive damage to the data on the volume which will only become
445 apparent when you try to use the volume again under Windows.
447 So when using linear raid, make sure that all your partitions have an even
448 number of sectors BEFORE attempting to use it. You have been warned!
450 Even better is to simply use the Device-Mapper for linear raid and then you do
451 not have this problem with odd numbers of sectors.