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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 EST.

	The Linux NTFS filesystem driver
	================================
	
	
	Table of contents
	=================
	
	- Overview
	- Web site
	- Features
	- Supported mount options
	- Known bugs and (mis-)features
	- Using NTFS volume and stripe sets
	  - The Device-Mapper driver
	  - The Software RAID / MD driver
	  - Limitations when using the MD driver
	
	
	Overview
	========
	
	Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
	These include mkntfs, a full-featured ntfs filesystem 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://www.linux-ntfs.org/
	
	The web site has a lot of additional information, such as a comprehensive
	FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS
	userspace utilities, etc.
	
	
	Features
	========
	
	- This is a complete rewrite of the NTFS driver that used to be in the 2.4 and
	  earlier kernels.  This new driver implements NTFS read support and is
	  functionally equivalent to the old ntfs driver and it also implements limited
	  write support.  The biggest limitation at present is that files/directories
	  cannot be created or deleted.  See below for the list of write features that
	  are so far supported.  Another limitation is that writing to compressed files
	  is not implemented at all.  Also, neither read nor write access to encrypted
	  files is so far implemented.
	- 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).
	- The new driver supports truncate(2) and open(2) with O_TRUNC.  But at present
	  only very limited support for highly fragmented files, i.e. ones which have
	  their data attribute split across multiple extents, is included.  Another
	  limitation is that at present truncate(2) will never create sparse files,
	  since to mark a file sparse we need to modify the directory entry for the
	  file and we do not implement directory modifications yet.
	- The new driver supports write(2) which can both overwrite existing data and
	  extend the file size so that you can write beyond the existing data.  Also,
	  writing into sparse regions is supported and the holes are filled in with
	  clusters.  But at present only limited support for highly fragmented files,
	  i.e. ones which have their data attribute split across multiple extents, is
	  included.  Another limitation is that write(2) will never create sparse
	  files, since to mark a file sparse we need to modify the directory entry for
	  the file and we do not implement directory modifications yet.
	
	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.
	
	disable_sparse=<BOOL>	If disable_sparse is specified, creation of sparse
				regions, i.e. holes, inside files is disabled for the
				volume (for the duration of this mount only).  By
				default, creation of sparse regions is enabled, which
				is consistent with the behaviour of traditional Unix
				filesystems.
	
	errors=opt		What to do when critical filesystem 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: linux-ntfs-dev@lists.sourceforge.net
	
	
	Using NTFS volume and stripe sets
	=================================
	
	For support of volume and stripe sets, you can either use the kernel's
	Device-Mapper driver or the kernel's Software RAID / MD driver.  The former is
	the recommended one to use for linear raid.  But the latter is required for
	raid level 5.  For striping and mirroring, either driver should work fine.
	
	
	The Device-Mapper driver
	------------------------
	
	You will need to create a table of the components of the volume/stripe set and
	how they fit together and load this into the kernel using the dmsetup utility
	(see man 8 dmsetup).
	
	Linear volume sets, i.e. linear raid, has been tested and works fine.  Even
	though untested, there is no reason why stripe sets, i.e. raid level 0, and
	mirrors, i.e. raid level 1 should not work, too.  Stripes with parity, i.e.
	raid level 5, unfortunately cannot work yet because the current version of the
	Device-Mapper driver does not support raid level 5.  You may be able to use the
	Software RAID / MD driver for raid level 5, see the next section for details.
	
	To create the table describing your volume you will need to know each of its
	components and their sizes in sectors, i.e. multiples of 512-byte blocks.
	
	For NT4 fault tolerant volumes you can obtain the sizes using fdisk.  So for
	example if one of your partitions is /dev/hda2 you would do:
	
	$ fdisk -ul /dev/hda
	
	Disk /dev/hda: 81.9 GB, 81964302336 bytes
	255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors
	Units = sectors of 1 * 512 = 512 bytes
	
	   Device Boot      Start         End      Blocks   Id  System
	   /dev/hda1   *          63     4209029     2104483+  83  Linux
	   /dev/hda2         4209030    37768814    16779892+  86  NTFS
	   /dev/hda3        37768815    46170809     4200997+  83  Linux
	
	And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 =
	33559785 sectors.
	
	For Win2k and later dynamic disks, you can for example use the ldminfo utility
	which is part of the Linux LDM tools (the latest version at the time of
	writing is linux-ldm-0.0.8.tar.bz2).  You can download it from:
		http://www.linux-ntfs.org/
	Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go
	into it (cd linux-ldm-0.0.8) and change to the test directory (cd test).  You
	will find the precompiled (i386) ldminfo utility there.  NOTE: You will not be
	able to compile this yourself easily so use the binary version!
	
	Then you would use ldminfo in dump mode to obtain the necessary information:
	
	$ ./ldminfo --dump /dev/hda
	
	This would dump the LDM database found on /dev/hda which describes all of your
	dynamic disks and all the volumes on them.  At the bottom you will see the
	VOLUME DEFINITIONS section which is all you really need.  You may need to look
	further above to determine which of the disks in the volume definitions is
	which device in Linux.  Hint: Run ldminfo on each of your dynamic disks and
	look at the Disk Id close to the top of the output for each (the PRIVATE HEADER
	section).  You can then find these Disk Ids in the VBLK DATABASE section in the
	<Disk> components where you will get the LDM Name for the disk that is found in
	the VOLUME DEFINITIONS section.
	
	Note you will also need to enable the LDM driver in the Linux kernel.  If your
	distribution did not enable it, you will need to recompile the kernel with it
	enabled.  This will create the LDM partitions on each device at boot time.  You
	would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc)
	in the Device-Mapper table.
	
	You can also bypass using the LDM driver by using the main device (e.g.
	/dev/hda) and then using the offsets of the LDM partitions into this device as
	the "Start sector of device" when creating the table.  Once again ldminfo would
	give you the correct information to do this.
	
	Assuming you know all your devices and their sizes things are easy.
	
	For a linear raid the table would look like this (note all values are in
	512-byte sectors):
	
	--- cut here ---
	# Offset into	Size of this	Raid type	Device		Start sector
	# volume	device						of device
	0		1028161		linear		/dev/hda1	0
	1028161		3903762		linear		/dev/hdb2	0
	4931923		2103211		linear		/dev/hdc1	0
	--- cut here ---
	
	For a striped volume, i.e. raid level 0, you will need to know the chunk size
	you used when creating the volume.  Windows uses 64kiB as the default, so it
	will probably be this unless you changes the defaults when creating the array.
	
	For a raid level 0 the table would look like this (note all values are in
	512-byte sectors):
	
	--- cut here ---
	# Offset   Size	    Raid     Number   Chunk  1st        Start	2nd	  Start
	# into     of the   type     of	      size   Device	in	Device	  in
	# volume   volume	     stripes			device		  device
	0	   2056320  striped  2	      128    /dev/hda1	0	/dev/hdb1 0
	--- cut here ---
	
	If there are more than two devices, just add each of them to the end of the
	line.
	
	Finally, for a mirrored volume, i.e. raid level 1, the table would look like
	this (note all values are in 512-byte sectors):
	
	--- cut here ---
	# Ofs Size   Raid   Log  Number Region Should Number Source  Start Target Start
	# in  of the type   type of log size   sync?  of     Device  in    Device in
	# vol volume		 params		     mirrors	     Device	  Device
	0    2056320 mirror core 2	16     nosync 2	   /dev/hda1 0   /dev/hdb1 0
	--- cut here ---
	
	If you are mirroring to multiple devices you can specify further targets at the
	end of the line.
	
	Note the "Should sync?" parameter "nosync" means that the two mirrors are
	already in sync which will be the case on a clean shutdown of Windows.  If the
	mirrors are not clean, you can specify the "sync" option instead of "nosync"
	and the Device-Mapper driver will then copy the entirety of the "Source Device"
	to the "Target Device" or if you specified multiple target devices to all of
	them.
	
	Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1),
	and hand it over to dmsetup to work with, like so:
	
	$ dmsetup create myvolume1 /etc/ntfsvolume1
	
	You can obviously replace "myvolume1" with whatever name you like.
	
	If it all worked, you will now have the device /dev/device-mapper/myvolume1
	which you can then just use as an argument to the mount command as usual to
	mount the ntfs volume.  For example:
	
	$ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1
	
	(You need to create the directory /mnt/myvol1 first and of course you can use
	anything you like instead of /mnt/myvol1 as long as it is an existing
	directory.)
	
	It is advisable to do the mount read-only to see if the volume has been setup
	correctly to avoid the possibility of causing damage to the data on the ntfs
	volume.
	
	
	The Software RAID / MD driver
	-----------------------------
	
	An alternative to using the Device-Mapper driver is to use the kernel's
	Software RAID / MD driver.  For which you need to 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 "Limitations 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 damage 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-disk	1
	
	For linear raid, just change the raid-level above to "raid-level linear", for
	mirrors, change it to "raid-level 1", and for stripe sets with parity, change
	it to "raid-level 5".
	
	Note for stripe sets with parity you will also need to tell the MD driver
	which parity algorithm to use by specifying the option "parity-algorithm
	which", where you need to replace "which" with the name of the algorithm to
	use (see man 5 raidtab for available algorithms) and you will have to try the
	different available algorithms until you find one that works.  Make sure you
	are working read-only when playing with this as you may damage your data
	otherwise.  If you find which algorithm works please let us know (email the
	linux-ntfs developers list linux-ntfs-dev@lists.sourceforge.net or drop in on
	IRC in channel #ntfs on the irc.freenode.net network) so we can update this
	documentation.
	
	Once the raidtab is setup, run for example raid0run -a to start all devices or
	raid0run /dev/md0 to start a particular md device, in this case /dev/md0.
	
	Then just use the mount command as usual to mount the ntfs volume using for
	example:	mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume
	
	It is advisable to do the mount read-only to see if the md volume has been
	setup correctly to avoid the possibility of causing damage to the data on the
	ntfs volume.
	
	
	Limitations when using the Software RAID / MD driver
	-----------------------------------------------------
	
	Using the md driver will not work properly if any of your NTFS partitions have
	an odd number of sectors.  This is especially important for linear raid as all
	data after the first partition with an odd number of sectors will be offset by
	one or more sectors so if you mount such a partition with write support you
	will cause massive damage to the data on the volume which will only become
	apparent when you try to use the volume again under Windows.
	
	So when using linear raid, make sure that all your partitions have an even
	number of sectors BEFORE attempting to use it.  You have been warned!
	
	Even better is to simply use the Device-Mapper for linear raid and then you do
	not have this problem with odd numbers of sectors.

• [ filesystems ]
• 00-INDEX
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• [ caching ]
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• [ nfs ]
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• [ pohmelfs ]
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•