ntfs.txt

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The Linux NTFS filesystem driver
================================


Table of contents
=================

- Overview
- Web site
- Features
- Supported mount options
- Known bugs and (mis-)features
- Using Software RAID with NTFS
- Limitiations when using the MD driver
- ChangeLog


Overview
========

Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
These include mkntfs, a full-featured ntfs file system format utility,
ntfsundelete used for recovering files that were unintentionally deleted
from an NTFS volume and ntfsresize which is used to resize an NTFS partition.
See the web site for more information.

To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file
system type 'ntfs'.  The driver currently supports read-only mode (with no
fault-tolerance, encryption or journalling) and very limited, but safe, write
support.

For fault tolerance and raid support (i.e. volume and stripe sets), you can
use the kernel's Software RAID / MD driver.  See section "Using Software RAID
with NTFS" for details.


Web site
========

There is plenty of additional information on the linux-ntfs web site
at http://linux-ntfs.sourceforge.net/

The web site has a lot of additional information, such as a comprehensive
FAQ, documentation on the NTFS on-disk format, informaiton on the Linux-NTFS
userspace utilities, etc.


Features
========

- This is a complete rewrite of the NTFS driver that used to be in the kernel.
  This new driver implements NTFS read support and is functionally equivalent
  to the old ntfs driver.
- The new driver has full support for sparse files on NTFS 3.x volumes which
  the old driver isn't happy with.
- The new driver supports execution of binaries due to mmap() now being
  supported.
- The new driver supports loopback mounting of files on NTFS which is used by
  some Linux distributions to enable the user to run Linux from an NTFS
  partition by creating a large file while in Windows and then loopback
  mounting the file while in Linux and creating a Linux filesystem on it that
  is used to install Linux on it.
- A comparison of the two drivers using:
	time find . -type f -exec md5sum "{}" \;
  run three times in sequence with each driver (after a reboot) on a 1.4GiB
  NTFS partition, showed the new driver to be 20% faster in total time elapsed
  (from 9:43 minutes on average down to 7:53).  The time spent in user space
  was unchanged but the time spent in the kernel was decreased by a factor of
  2.5 (from 85 CPU seconds down to 33).
- The driver does not support short file names in general.  For backwards
  compatibility, we implement access to files using their short file names if
  they exist.  The driver will not create short file names however, and a
  rename will discard any existing short file name.
- The new driver supports exporting of mounted NTFS volumes via NFS.
- The new driver supports async io (aio).
- The new driver supports fsync(2), fdatasync(2), and msync(2).
- The new driver supports readv(2) and writev(2).
- The new driver supports access time updates (including mtime and ctime).


Supported mount options
=======================

In addition to the generic mount options described by the manual page for the
mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the
following mount options:

iocharset=name		Deprecated option.  Still supported but please use
			nls=name in the future.  See description for nls=name.

nls=name		Character set to use when returning file names.
			Unlike VFAT, NTFS suppresses names that contain
			unconvertible characters.  Note that most character
			sets contain insufficient characters to represent all
			possible Unicode characters that can exist on NTFS.
			To be sure you are not missing any files, you are
			advised to use nls=utf8 which is capable of
			representing all Unicode characters.

utf8=<bool>		Option no longer supported.  Currently mapped to
			nls=utf8 but please use nls=utf8 in the future and
			make sure utf8 is compiled either as module or into
			the kernel.  See description for nls=name.

uid=
gid=
umask=			Provide default owner, group, and access mode mask.
			These options work as documented in mount(8).  By
			default, the files/directories are owned by root and
			he/she has read and write permissions, as well as
			browse permission for directories.  No one else has any
			access permissions.  I.e. the mode on all files is by
			default rw------- and for directories rwx------, a
			consequence of the default fmask=0177 and dmask=0077.
			Using a umask of zero will grant all permissions to
			everyone, i.e. all files and directories will have mode
			rwxrwxrwx.

fmask=
dmask=			Instead of specifying umask which applies both to
			files and directories, fmask applies only to files and
			dmask only to directories.

sloppy=<BOOL>		If sloppy is specified, ignore unknown mount options.
			Otherwise the default behaviour is to abort mount if
			any unknown options are found.

show_sys_files=<BOOL>	If show_sys_files is specified, show the system files
			in directory listings.  Otherwise the default behaviour
			is to hide the system files.
			Note that even when show_sys_files is specified, "$MFT"
			will not be visible due to bugs/mis-features in glibc.
			Further, note that irrespective of show_sys_files, all
			files are accessible by name, i.e. you can always do
			"ls -l \$UpCase" for example to specifically show the
			system file containing the Unicode upcase table.

case_sensitive=<BOOL>	If case_sensitive is specified, treat all file names as
			case sensitive and create file names in the POSIX
			namespace.  Otherwise the default behaviour is to treat
			file names as case insensitive and to create file names
			in the WIN32/LONG name space.  Note, the Linux NTFS
			driver will never create short file names and will
			remove them on rename/delete of the corresponding long
			file name.
			Note that files remain accessible via their short file
			name, if it exists.  If case_sensitive, you will need
			to provide the correct case of the short file name.

errors=opt		What to do when critical file system errors are found.
			Following values can be used for "opt":
			  continue: DEFAULT, try to clean-up as much as
				    possible, e.g. marking a corrupt inode as
				    bad so it is no longer accessed, and then
				    continue.
			  recover:  At present only supported is recovery of
				    the boot sector from the backup copy.
				    If read-only mount, the recovery is done
				    in memory only and not written to disk.
			Note that the options are additive, i.e. specifying:
			   errors=continue,errors=recover
			means the driver will attempt to recover and if that
			fails it will clean-up as much as possible and
			continue.

mft_zone_multiplier=	Set the MFT zone multiplier for the volume (this
			setting is not persistent across mounts and can be
			changed from mount to mount but cannot be changed on
			remount).  Values of 1 to 4 are allowed, 1 being the
			default.  The MFT zone multiplier determines how much
			space is reserved for the MFT on the volume.  If all
			other space is used up, then the MFT zone will be
			shrunk dynamically, so this has no impact on the
			amount of free space.  However, it can have an impact
			on performance by affecting fragmentation of the MFT.
			In general use the default.  If you have a lot of small
			files then use a higher value.  The values have the
			following meaning:
			      Value	     MFT zone size (% of volume size)
				1		12.5%
				2		25%
				3		37.5%
				4		50%
			Note this option is irrelevant for read-only mounts.


Known bugs and (mis-)features
=============================

- The link count on each directory inode entry is set to 1, due to Linux not
  supporting directory hard links.  This may well confuse some user space
  applications, since the directory names will have the same inode numbers.
  This also speeds up ntfs_read_inode() immensely.  And we haven't found any
  problems with this approach so far.  If you find a problem with this, please
  let us know.


Please send bug reports/comments/feedback/abuse to the Linux-NTFS development
list at sourceforge: [e-mail]


Using Software RAID with NTFS
=============================

For support of volume and stripe sets, use the kernel's Software RAID / MD
driver and set up your /etc/raidtab appropriately (see man 5 raidtab).

Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level
0, have been tested and work fine (though see section "Limitiations when using
the MD driver with NTFS volumes" especially if you want to use linear raid).
Even though untested, there is no reason why mirrors, i.e. raid level 1, and
stripes with parity, i.e. raid level 5, should not work, too.

You have to use the "persistent-superblock 0" option for each raid-disk in the
NTFS volume/stripe you are configuring in /etc/raidtab as the persistent
superblock used by the MD driver would damange the NTFS volume.

Windows by default uses a stripe chunk size of 64k, so you probably want the
"chunk-size 64k" option for each raid-disk, too.

For example, if you have a stripe set consisting of two partitions /dev/hda5
and /dev/hdb1 your /etc/raidtab would look like this:

raiddev /dev/md0
	raid-level	0
	nr-raid-disks	2
	nr-spare-disks	0
	persistent-superblock	0
	chunk-size	64k
	device		/dev/hda5
	raid-disk	0
	device		/dev/hdb1
	raid-disl	1