1The Linux NTFS filesystem driver 2================================ 3 4 5Table of contents 6================= 7 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 17 18 19Overview 20======== 21 22Linux-NTFS comes with a number of user-space programs known as ntfsprogs. 23These include mkntfs, a full-featured ntfs filesystem format utility, 24ntfsundelete used for recovering files that were unintentionally deleted 25from an NTFS volume and ntfsresize which is used to resize an NTFS partition. 26See the web site for more information. 27 28To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file 29system type 'ntfs'. The driver currently supports read-only mode (with no 30fault-tolerance, encryption or journalling) and very limited, but safe, write 31support. 32 33For fault tolerance and raid support (i.e. volume and stripe sets), you can 34use the kernel's Software RAID / MD driver. See section "Using Software RAID 35with NTFS" for details. 36 37 38Web site 39======== 40 41There is plenty of additional information on the linux-ntfs web site 42at http://www.linux-ntfs.org/ 43 44The web site has a lot of additional information, such as a comprehensive 45FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS 46userspace utilities, etc. 47 48 49Features 50======== 51 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. 99 100Supported mount options 101======================= 102 103In addition to the generic mount options described by the manual page for the 104mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the 105following mount options: 106 107iocharset=name Deprecated option. Still supported but please use 108 nls=name in the future. See description for nls=name. 109 110nls=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. 118 119utf8=<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. 123 124uid= 125gid= 126umask= 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. 137 138fmask= 139dmask= Instead of specifying umask which applies both to 140 files and directories, fmask applies only to files and 141 dmask only to directories. 142 143sloppy=<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. 146 147show_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. 156 157case_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. 168 169disable_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. 175 176errors=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. 191 192mft_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. 211 212 213Known bugs and (mis-)features 214============================= 215 216- 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. 222 223 224Please send bug reports/comments/feedback/abuse to the Linux-NTFS development 225list at sourceforge: linux-ntfs-dev@lists.sourceforge.net 226 227 228Using NTFS volume and stripe sets 229================================= 230 231For support of volume and stripe sets, you can either use the kernel's 232Device-Mapper driver or the kernel's Software RAID / MD driver. The former is 233the recommended one to use for linear raid. But the latter is required for 234raid level 5. For striping and mirroring, either driver should work fine. 235 236 237The Device-Mapper driver 238------------------------ 239 240You will need to create a table of the components of the volume/stripe set and 241how they fit together and load this into the kernel using the dmsetup utility 242(see man 8 dmsetup). 243 244Linear volume sets, i.e. linear raid, has been tested and works fine. Even 245though untested, there is no reason why stripe sets, i.e. raid level 0, and 246mirrors, i.e. raid level 1 should not work, too. Stripes with parity, i.e. 247raid level 5, unfortunately cannot work yet because the current version of the 248Device-Mapper driver does not support raid level 5. You may be able to use the 249Software RAID / MD driver for raid level 5, see the next section for details. 250 251To create the table describing your volume you will need to know each of its 252components and their sizes in sectors, i.e. multiples of 512-byte blocks. 253 254For NT4 fault tolerant volumes you can obtain the sizes using fdisk. So for 255example if one of your partitions is /dev/hda2 you would do: 256 257$ fdisk -ul /dev/hda 258 259Disk /dev/hda: 81.9 GB, 81964302336 bytes 260255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors 261Units = sectors of 1 * 512 = 512 bytes 262 263 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 267 268And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 = 26933559785 sectors. 270 271For Win2k and later dynamic disks, you can for example use the ldminfo utility 272which is part of the Linux LDM tools (the latest version at the time of 273writing is linux-ldm-0.0.8.tar.bz2). You can download it from: 274 http://www.linux-ntfs.org/ 275Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go 276into it (cd linux-ldm-0.0.8) and change to the test directory (cd test). You 277will find the precompiled (i386) ldminfo utility there. NOTE: You will not be 278able to compile this yourself easily so use the binary version! 279 280Then you would use ldminfo in dump mode to obtain the necessary information: 281 282$ ./ldminfo --dump /dev/hda 283 284This would dump the LDM database found on /dev/hda which describes all of your 285dynamic disks and all the volumes on them. At the bottom you will see the 286VOLUME DEFINITIONS section which is all you really need. You may need to look 287further above to determine which of the disks in the volume definitions is 288which device in Linux. Hint: Run ldminfo on each of your dynamic disks and 289look at the Disk Id close to the top of the output for each (the PRIVATE HEADER 290section). 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 292the VOLUME DEFINITIONS section. 293 294Note you will also need to enable the LDM driver in the Linux kernel. If your 295distribution did not enable it, you will need to recompile the kernel with it 296enabled. This will create the LDM partitions on each device at boot time. You 297would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc) 298in the Device-Mapper table. 299 300You 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 302the "Start sector of device" when creating the table. Once again ldminfo would 303give you the correct information to do this. 304 305Assuming you know all your devices and their sizes things are easy. 306 307For a linear raid the table would look like this (note all values are in 308512-byte sectors): 309 310--- cut here --- 311# Offset into Size of this Raid type Device Start sector 312# volume device of device 3130 1028161 linear /dev/hda1 0 3141028161 3903762 linear /dev/hdb2 0 3154931923 2103211 linear /dev/hdc1 0 316--- cut here --- 317 318For a striped volume, i.e. raid level 0, you will need to know the chunk size 319you used when creating the volume. Windows uses 64kiB as the default, so it 320will probably be this unless you changes the defaults when creating the array. 321 322For a raid level 0 the table would look like this (note all values are in 323512-byte sectors): 324 325--- 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 3290 2056320 striped 2 128 /dev/hda1 0 /dev/hdb1 0 330--- cut here --- 331 332If there are more than two devices, just add each of them to the end of the 333line. 334 335Finally, for a mirrored volume, i.e. raid level 1, the table would look like 336this (note all values are in 512-byte sectors): 337 338--- 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 3420 2056320 mirror core 2 16 nosync 2 /dev/hda1 0 /dev/hdb1 0 343--- cut here --- 344 345If you are mirroring to multiple devices you can specify further targets at the 346end of the line. 347 348Note the "Should sync?" parameter "nosync" means that the two mirrors are 349already in sync which will be the case on a clean shutdown of Windows. If the 350mirrors are not clean, you can specify the "sync" option instead of "nosync" 351and the Device-Mapper driver will then copy the entirety of the "Source Device" 352to the "Target Device" or if you specified multiple target devices to all of 353them. 354 355Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1), 356and hand it over to dmsetup to work with, like so: 357 358$ dmsetup create myvolume1 /etc/ntfsvolume1 359 360You can obviously replace "myvolume1" with whatever name you like. 361 362If it all worked, you will now have the device /dev/device-mapper/myvolume1 363which you can then just use as an argument to the mount command as usual to 364mount the ntfs volume. For example: 365 366$ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1 367 368(You need to create the directory /mnt/myvol1 first and of course you can use 369anything you like instead of /mnt/myvol1 as long as it is an existing 370directory.) 371 372It is advisable to do the mount read-only to see if the volume has been setup 373correctly to avoid the possibility of causing damage to the data on the ntfs 374volume. 375 376 377The Software RAID / MD driver 378----------------------------- 379 380An alternative to using the Device-Mapper driver is to use the kernel's 381Software RAID / MD driver. For which you need to set up your /etc/raidtab 382appropriately (see man 5 raidtab). 383 384Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level 3850, have been tested and work fine (though see section "Limitations when using 386the MD driver with NTFS volumes" especially if you want to use linear raid). 387Even though untested, there is no reason why mirrors, i.e. raid level 1, and 388stripes with parity, i.e. raid level 5, should not work, too. 389 390You have to use the "persistent-superblock 0" option for each raid-disk in the 391NTFS volume/stripe you are configuring in /etc/raidtab as the persistent 392superblock used by the MD driver would damage the NTFS volume. 393 394Windows by default uses a stripe chunk size of 64k, so you probably want the 395"chunk-size 64k" option for each raid-disk, too. 396 397For example, if you have a stripe set consisting of two partitions /dev/hda5 398and /dev/hdb1 your /etc/raidtab would look like this: 399 400raiddev /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 1 410 411For linear raid, just change the raid-level above to "raid-level linear", for 412mirrors, change it to "raid-level 1", and for stripe sets with parity, change 413it to "raid-level 5". 414 415Note for stripe sets with parity you will also need to tell the MD driver 416which parity algorithm to use by specifying the option "parity-algorithm 417which", where you need to replace "which" with the name of the algorithm to 418use (see man 5 raidtab for available algorithms) and you will have to try the 419different available algorithms until you find one that works. Make sure you 420are working read-only when playing with this as you may damage your data 421otherwise. If you find which algorithm works please let us know (email the 422linux-ntfs developers list linux-ntfs-dev@lists.sourceforge.net or drop in on 423IRC in channel #ntfs on the irc.freenode.net network) so we can update this 424documentation. 425 426Once the raidtab is setup, run for example raid0run -a to start all devices or 427raid0run /dev/md0 to start a particular md device, in this case /dev/md0. 428 429Then just use the mount command as usual to mount the ntfs volume using for 430example: mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume 431 432It is advisable to do the mount read-only to see if the md volume has been 433setup correctly to avoid the possibility of causing damage to the data on the 434ntfs volume. 435 436 437Limitations when using the Software RAID / MD driver 438----------------------------------------------------- 439 440Using the md driver will not work properly if any of your NTFS partitions have 441an odd number of sectors. This is especially important for linear raid as all 442data after the first partition with an odd number of sectors will be offset by 443one or more sectors so if you mount such a partition with write support you 444will cause massive damage to the data on the volume which will only become 445apparent when you try to use the volume again under Windows. 446 447So when using linear raid, make sure that all your partitions have an even 448number of sectors BEFORE attempting to use it. You have been warned! 449 450Even better is to simply use the Device-Mapper for linear raid and then you do 451not have this problem with odd numbers of sectors. 452
