1 .. SPDX-License-Identifier: GPL-2.0
3 ================================
4 The Linux NTFS filesystem driver
5 ================================
13 - Supported mount options
14 - Known bugs and (mis-)features
15 - Using NTFS volume and stripe sets
16 - The Device-Mapper driver
17 - The Software RAID / MD driver
18 - Limitations when using the MD driver
24 Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
25 These include mkntfs, a full-featured ntfs filesystem format utility,
26 ntfsundelete used for recovering files that were unintentionally deleted
27 from an NTFS volume and ntfsresize which is used to resize an NTFS partition.
28 See the web site for more information.
30 To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file
31 system type 'ntfs'. The driver currently supports read-only mode (with no
32 fault-tolerance, encryption or journalling) and very limited, but safe, write
35 For fault tolerance and raid support (i.e. volume and stripe sets), you can
36 use the kernel's Software RAID / MD driver. See section "Using Software RAID
37 with NTFS" for details.
43 There is plenty of additional information on the linux-ntfs web site
44 at http://www.linux-ntfs.org/
46 The web site has a lot of additional information, such as a comprehensive
47 FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS
48 userspace utilities, etc.
54 - This is a complete rewrite of the NTFS driver that used to be in the 2.4 and
55 earlier kernels. This new driver implements NTFS read support and is
56 functionally equivalent to the old ntfs driver and it also implements limited
57 write support. The biggest limitation at present is that files/directories
58 cannot be created or deleted. See below for the list of write features that
59 are so far supported. Another limitation is that writing to compressed files
60 is not implemented at all. Also, neither read nor write access to encrypted
61 files is so far implemented.
62 - The new driver has full support for sparse files on NTFS 3.x volumes which
63 the old driver isn't happy with.
64 - The new driver supports execution of binaries due to mmap() now being
66 - The new driver supports loopback mounting of files on NTFS which is used by
67 some Linux distributions to enable the user to run Linux from an NTFS
68 partition by creating a large file while in Windows and then loopback
69 mounting the file while in Linux and creating a Linux filesystem on it that
70 is used to install Linux on it.
71 - A comparison of the two drivers using::
73 time find . -type f -exec md5sum "{}" \;
75 run three times in sequence with each driver (after a reboot) on a 1.4GiB
76 NTFS partition, showed the new driver to be 20% faster in total time elapsed
77 (from 9:43 minutes on average down to 7:53). The time spent in user space
78 was unchanged but the time spent in the kernel was decreased by a factor of
79 2.5 (from 85 CPU seconds down to 33).
80 - The driver does not support short file names in general. For backwards
81 compatibility, we implement access to files using their short file names if
82 they exist. The driver will not create short file names however, and a
83 rename will discard any existing short file name.
84 - The new driver supports exporting of mounted NTFS volumes via NFS.
85 - The new driver supports async io (aio).
86 - The new driver supports fsync(2), fdatasync(2), and msync(2).
87 - The new driver supports readv(2) and writev(2).
88 - The new driver supports access time updates (including mtime and ctime).
89 - The new driver supports truncate(2) and open(2) with O_TRUNC. But at present
90 only very limited support for highly fragmented files, i.e. ones which have
91 their data attribute split across multiple extents, is included. Another
92 limitation is that at present truncate(2) will never create sparse files,
93 since to mark a file sparse we need to modify the directory entry for the
94 file and we do not implement directory modifications yet.
95 - The new driver supports write(2) which can both overwrite existing data and
96 extend the file size so that you can write beyond the existing data. Also,
97 writing into sparse regions is supported and the holes are filled in with
98 clusters. But at present only limited support for highly fragmented files,
99 i.e. ones which have their data attribute split across multiple extents, is
100 included. Another limitation is that write(2) will never create sparse
101 files, since to mark a file sparse we need to modify the directory entry for
102 the file and we do not implement directory modifications yet.
104 Supported mount options
105 =======================
107 In addition to the generic mount options described by the manual page for the
108 mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the
109 following mount options:
111 ======================= =======================================================
112 iocharset=name Deprecated option. Still supported but please use
113 nls=name in the future. See description for nls=name.
115 nls=name Character set to use when returning file names.
116 Unlike VFAT, NTFS suppresses names that contain
117 unconvertible characters. Note that most character
118 sets contain insufficient characters to represent all
119 possible Unicode characters that can exist on NTFS.
120 To be sure you are not missing any files, you are
121 advised to use nls=utf8 which is capable of
122 representing all Unicode characters.
124 utf8=<bool> Option no longer supported. Currently mapped to
125 nls=utf8 but please use nls=utf8 in the future and
126 make sure utf8 is compiled either as module or into
127 the kernel. See description for nls=name.
131 umask= Provide default owner, group, and access mode mask.
132 These options work as documented in mount(8). By
133 default, the files/directories are owned by root and
134 he/she has read and write permissions, as well as
135 browse permission for directories. No one else has any
136 access permissions. I.e. the mode on all files is by
137 default rw------- and for directories rwx------, a
138 consequence of the default fmask=0177 and dmask=0077.
139 Using a umask of zero will grant all permissions to
140 everyone, i.e. all files and directories will have mode
144 dmask= Instead of specifying umask which applies both to
145 files and directories, fmask applies only to files and
146 dmask only to directories.
148 sloppy=<BOOL> If sloppy is specified, ignore unknown mount options.
149 Otherwise the default behaviour is to abort mount if
150 any unknown options are found.
152 show_sys_files=<BOOL> If show_sys_files is specified, show the system files
153 in directory listings. Otherwise the default behaviour
154 is to hide the system files.
155 Note that even when show_sys_files is specified, "$MFT"
156 will not be visible due to bugs/mis-features in glibc.
157 Further, note that irrespective of show_sys_files, all
158 files are accessible by name, i.e. you can always do
159 "ls -l \$UpCase" for example to specifically show the
160 system file containing the Unicode upcase table.
162 case_sensitive=<BOOL> If case_sensitive is specified, treat all file names as
163 case sensitive and create file names in the POSIX
164 namespace. Otherwise the default behaviour is to treat
165 file names as case insensitive and to create file names
166 in the WIN32/LONG name space. Note, the Linux NTFS
167 driver will never create short file names and will
168 remove them on rename/delete of the corresponding long
170 Note that files remain accessible via their short file
171 name, if it exists. If case_sensitive, you will need
172 to provide the correct case of the short file name.
174 disable_sparse=<BOOL> If disable_sparse is specified, creation of sparse
175 regions, i.e. holes, inside files is disabled for the
176 volume (for the duration of this mount only). By
177 default, creation of sparse regions is enabled, which
178 is consistent with the behaviour of traditional Unix
181 errors=opt What to do when critical filesystem errors are found.
182 Following values can be used for "opt":
184 ======== =========================================
185 continue DEFAULT, try to clean-up as much as
186 possible, e.g. marking a corrupt inode as
187 bad so it is no longer accessed, and then
189 recover At present only supported is recovery of
190 the boot sector from the backup copy.
191 If read-only mount, the recovery is done
192 in memory only and not written to disk.
193 ======== =========================================
195 Note that the options are additive, i.e. specifying::
197 errors=continue,errors=recover
199 means the driver will attempt to recover and if that
200 fails it will clean-up as much as possible and
203 mft_zone_multiplier= Set the MFT zone multiplier for the volume (this
204 setting is not persistent across mounts and can be
205 changed from mount to mount but cannot be changed on
206 remount). Values of 1 to 4 are allowed, 1 being the
207 default. The MFT zone multiplier determines how much
208 space is reserved for the MFT on the volume. If all
209 other space is used up, then the MFT zone will be
210 shrunk dynamically, so this has no impact on the
211 amount of free space. However, it can have an impact
212 on performance by affecting fragmentation of the MFT.
213 In general use the default. If you have a lot of small
214 files then use a higher value. The values have the
217 ===== =================================
218 Value MFT zone size (% of volume size)
219 ===== =================================
224 ===== =================================
226 Note this option is irrelevant for read-only mounts.
227 ======================= =======================================================
230 Known bugs and (mis-)features
231 =============================
233 - The link count on each directory inode entry is set to 1, due to Linux not
234 supporting directory hard links. This may well confuse some user space
235 applications, since the directory names will have the same inode numbers.
236 This also speeds up ntfs_read_inode() immensely. And we haven't found any
237 problems with this approach so far. If you find a problem with this, please
241 Please send bug reports/comments/feedback/abuse to the Linux-NTFS development
242 list at sourceforge: linux-ntfs-dev@lists.sourceforge.net
245 Using NTFS volume and stripe sets
246 =================================
248 For support of volume and stripe sets, you can either use the kernel's
249 Device-Mapper driver or the kernel's Software RAID / MD driver. The former is
250 the recommended one to use for linear raid. But the latter is required for
251 raid level 5. For striping and mirroring, either driver should work fine.
254 The Device-Mapper driver
255 ------------------------
257 You will need to create a table of the components of the volume/stripe set and
258 how they fit together and load this into the kernel using the dmsetup utility
261 Linear volume sets, i.e. linear raid, has been tested and works fine. Even
262 though untested, there is no reason why stripe sets, i.e. raid level 0, and
263 mirrors, i.e. raid level 1 should not work, too. Stripes with parity, i.e.
264 raid level 5, unfortunately cannot work yet because the current version of the
265 Device-Mapper driver does not support raid level 5. You may be able to use the
266 Software RAID / MD driver for raid level 5, see the next section for details.
268 To create the table describing your volume you will need to know each of its
269 components and their sizes in sectors, i.e. multiples of 512-byte blocks.
271 For NT4 fault tolerant volumes you can obtain the sizes using fdisk. So for
272 example if one of your partitions is /dev/hda2 you would do::
276 Disk /dev/hda: 81.9 GB, 81964302336 bytes
277 255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors
278 Units = sectors of 1 * 512 = 512 bytes
280 Device Boot Start End Blocks Id System
281 /dev/hda1 * 63 4209029 2104483+ 83 Linux
282 /dev/hda2 4209030 37768814 16779892+ 86 NTFS
283 /dev/hda3 37768815 46170809 4200997+ 83 Linux
285 And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 =
288 For Win2k and later dynamic disks, you can for example use the ldminfo utility
289 which is part of the Linux LDM tools (the latest version at the time of
290 writing is linux-ldm-0.0.8.tar.bz2). You can download it from:
292 http://www.linux-ntfs.org/
294 Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go
295 into it (cd linux-ldm-0.0.8) and change to the test directory (cd test). You
296 will find the precompiled (i386) ldminfo utility there. NOTE: You will not be
297 able to compile this yourself easily so use the binary version!
299 Then you would use ldminfo in dump mode to obtain the necessary information::
301 $ ./ldminfo --dump /dev/hda
303 This would dump the LDM database found on /dev/hda which describes all of your
304 dynamic disks and all the volumes on them. At the bottom you will see the
305 VOLUME DEFINITIONS section which is all you really need. You may need to look
306 further above to determine which of the disks in the volume definitions is
307 which device in Linux. Hint: Run ldminfo on each of your dynamic disks and
308 look at the Disk Id close to the top of the output for each (the PRIVATE HEADER
309 section). You can then find these Disk Ids in the VBLK DATABASE section in the
310 <Disk> components where you will get the LDM Name for the disk that is found in
311 the VOLUME DEFINITIONS section.
313 Note you will also need to enable the LDM driver in the Linux kernel. If your
314 distribution did not enable it, you will need to recompile the kernel with it
315 enabled. This will create the LDM partitions on each device at boot time. You
316 would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc)
317 in the Device-Mapper table.
319 You can also bypass using the LDM driver by using the main device (e.g.
320 /dev/hda) and then using the offsets of the LDM partitions into this device as
321 the "Start sector of device" when creating the table. Once again ldminfo would
322 give you the correct information to do this.
324 Assuming you know all your devices and their sizes things are easy.
326 For a linear raid the table would look like this (note all values are in
329 # Offset into Size of this Raid type Device Start sector
330 # volume device of device
331 0 1028161 linear /dev/hda1 0
332 1028161 3903762 linear /dev/hdb2 0
333 4931923 2103211 linear /dev/hdc1 0
335 For a striped volume, i.e. raid level 0, you will need to know the chunk size
336 you used when creating the volume. Windows uses 64kiB as the default, so it
337 will probably be this unless you changes the defaults when creating the array.
339 For a raid level 0 the table would look like this (note all values are in
342 # Offset Size Raid Number Chunk 1st Start 2nd Start
343 # into of the type of size Device in Device in
344 # volume volume stripes device device
345 0 2056320 striped 2 128 /dev/hda1 0 /dev/hdb1 0
347 If there are more than two devices, just add each of them to the end of the
350 Finally, for a mirrored volume, i.e. raid level 1, the table would look like
351 this (note all values are in 512-byte sectors)::
353 # Ofs Size Raid Log Number Region Should Number Source Start Target Start
354 # in of the type type of log size sync? of Device in Device in
355 # vol volume params mirrors Device Device
356 0 2056320 mirror core 2 16 nosync 2 /dev/hda1 0 /dev/hdb1 0
358 If you are mirroring to multiple devices you can specify further targets at the
361 Note the "Should sync?" parameter "nosync" means that the two mirrors are
362 already in sync which will be the case on a clean shutdown of Windows. If the
363 mirrors are not clean, you can specify the "sync" option instead of "nosync"
364 and the Device-Mapper driver will then copy the entirety of the "Source Device"
365 to the "Target Device" or if you specified multiple target devices to all of
368 Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1),
369 and hand it over to dmsetup to work with, like so::
371 $ dmsetup create myvolume1 /etc/ntfsvolume1
373 You can obviously replace "myvolume1" with whatever name you like.
375 If it all worked, you will now have the device /dev/device-mapper/myvolume1
376 which you can then just use as an argument to the mount command as usual to
377 mount the ntfs volume. For example::
379 $ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1
381 (You need to create the directory /mnt/myvol1 first and of course you can use
382 anything you like instead of /mnt/myvol1 as long as it is an existing
385 It is advisable to do the mount read-only to see if the volume has been setup
386 correctly to avoid the possibility of causing damage to the data on the ntfs
390 The Software RAID / MD driver
391 -----------------------------
393 An alternative to using the Device-Mapper driver is to use the kernel's
394 Software RAID / MD driver. For which you need to set up your /etc/raidtab
395 appropriately (see man 5 raidtab).
397 Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level
398 0, have been tested and work fine (though see section "Limitations when using
399 the MD driver with NTFS volumes" especially if you want to use linear raid).
400 Even though untested, there is no reason why mirrors, i.e. raid level 1, and
401 stripes with parity, i.e. raid level 5, should not work, too.
403 You have to use the "persistent-superblock 0" option for each raid-disk in the
404 NTFS volume/stripe you are configuring in /etc/raidtab as the persistent
405 superblock used by the MD driver would damage the NTFS volume.
407 Windows by default uses a stripe chunk size of 64k, so you probably want the
408 "chunk-size 64k" option for each raid-disk, too.
410 For example, if you have a stripe set consisting of two partitions /dev/hda5
411 and /dev/hdb1 your /etc/raidtab would look like this::
417 persistent-superblock 0
424 For linear raid, just change the raid-level above to "raid-level linear", for
425 mirrors, change it to "raid-level 1", and for stripe sets with parity, change
426 it to "raid-level 5".
428 Note for stripe sets with parity you will also need to tell the MD driver
429 which parity algorithm to use by specifying the option "parity-algorithm
430 which", where you need to replace "which" with the name of the algorithm to
431 use (see man 5 raidtab for available algorithms) and you will have to try the
432 different available algorithms until you find one that works. Make sure you
433 are working read-only when playing with this as you may damage your data
434 otherwise. If you find which algorithm works please let us know (email the
435 linux-ntfs developers list linux-ntfs-dev@lists.sourceforge.net or drop in on
436 IRC in channel #ntfs on the irc.freenode.net network) so we can update this
439 Once the raidtab is setup, run for example raid0run -a to start all devices or
440 raid0run /dev/md0 to start a particular md device, in this case /dev/md0.
442 Then just use the mount command as usual to mount the ntfs volume using for
445 mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume
447 It is advisable to do the mount read-only to see if the md volume has been
448 setup correctly to avoid the possibility of causing damage to the data on the
452 Limitations when using the Software RAID / MD driver
453 -----------------------------------------------------
455 Using the md driver will not work properly if any of your NTFS partitions have
456 an odd number of sectors. This is especially important for linear raid as all
457 data after the first partition with an odd number of sectors will be offset by
458 one or more sectors so if you mount such a partition with write support you
459 will cause massive damage to the data on the volume which will only become
460 apparent when you try to use the volume again under Windows.
462 So when using linear raid, make sure that all your partitions have an even
463 number of sectors BEFORE attempting to use it. You have been warned!
465 Even better is to simply use the Device-Mapper for linear raid and then you do
466 not have this problem with odd numbers of sectors.
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