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BTRFS(8)			     btrfs			      BTRFS(8)

NAME
       btrfs - control a btrfs filesystem

SYNOPSIS
       btrfs subvolume snapshot [-r] <source> [<dest>/]<name>

       btrfs subvolume delete <subvolume> [<subvolume>...]

       btrfs subvolume create [<dest>/]<name>

       btrfs  subvolume	 list  [-acgoprts]  [-G	 [+|-]value]  [-C  [+|-]value]
       [--sort=rootid,gen,ogen,path] <path>

       btrfs subvolume set-default <id> <path>

       btrfs subvolume get-default <path>

       btrfs subvolume find-new <subvolume> <last_gen>

       btrfs subvolume show <path>

       btrfs filesystem defragment -c[zlib|lzo] [-l len] [-s start] [-t	 size]
       -[vf] <file>|<dir> [<file>|<dir>...]

       btrfs filesystem sync <path>

       btrfs  filesystem resize [devid:][+/-]<size>[gkm]|[devid:]max <filesys‐
       tem>

       btrfs filesystem label <dev> [newlabel]

       btrfs filesystem balance <path>

       btrfs device scan [--all-devices|<device> [<device>...]]

       btrfs device stats [-z] {<path>|<device>}

       btrfs device add <device> [<device>...] <path>

       btrfs device delete <device> [<device>...] <path>

       btrfs replace start [-Bfr] <srcdev>|<devid> <targetdev> <path>

       btrfs replace status [-1] <path>

       btrfs replace cancel <path>

       btrfs scrub start [-Bdqru] {<path>|<device>}

       btrfs scrub cancel {<path>|<device>}

       btrfs scrub resume [-Bdqru] {<path>|<device>}

       btrfs scrub status [-d] {<path>|<device>}

       btrfs inspect-internal inode-resolve [-v] <inode> <path>

       btrfs inspect-internal logical-resolve [-Pv] [-s size] <logical> <path>

       btrfs help|--help

       btrfs <command> --help

DESCRIPTION
       btrfs is used to control the filesystem and the files  and  directories
       stored.	It  is the tool to create or destroy a snapshot or a subvolume
       for the filesystem, to defrag a file or a directory, flush the data  to
       the disk, to resize the filesystem, to scan the device.

       It  is  possible	 to  abbreviate	 the commands unless the commands  are
       ambiguous.  For example: it is possible to run btrfs sub snaps  instead
       of  btrfs subvolume snapshot.  But btrfs file s is not allowed, because
       file s may be interpreted both as filesystem  show  and	as  filesystem
       sync.   In this case btrfs returns filesystem sync If a command is ter‐
       minated by --help , the detailed help is showed. If the passed  command
       matches	more  commands,	 detailed  help of all the matched commands is
       showed. For example btrfs dev --help shows the help of all device* com‐
       mands.

COMMANDS
       subvolume snapshot [-r] <source> [<dest>/]<name>
	      Create  a	 writable/readonly  snapshot of the subvolume <source>
	      with the name <name> in the <dest> directory. If <source> is not
	      a	 subvolume,  btrfs returns an error. If -r is given, the snap‐
	      shot will be readonly.

       subvolume delete <subvolume> [<subvolume>...]
	      Delete the subvolume <subvolume>. If <subvolume> is not  a  sub‐
	      volume, btrfs returns an error.

       subvolume create [<dest>/]<name>
	      Create  a	 subvolume  in	<dest> (or in the current directory if
	      <dest> is omitted).

       subvolume   list	  [-acgoprts]	[-G   [+|-]value]   [-C	   [+|-]value]
       [--sort=rootid,gen,ogen,path] <path>
	      List  the subvolumes present in the filesystem <path>. For every
	      subvolume the following information is  shown  by	 default.   ID
	      <ID>  top level <ID> path <path> where path is the relative path
	      of the subvolume to the top level subvolume.

	      The subvolume's ID may be used by the subvolume set-default com‐
	      mand,  or	 at  mount  time  via  the subvolid= option.  If -p is
	      given, then parent <ID> is added to the output  between  ID  and
	      top  level.  The	parent's  ID may be used at mount time via the
	      subvolrootid= option.

	      -t print the result as a table.

	      -a print all the subvolumes in the  filesystem  and  distinguish
	      between  absolute	 and  relative	path with respect to the given
	      <path>.

	      -c print the ogeneration of the subvolume, aliases: ogen or ori‐
	      gin generation

	      -g print the generation of the subvolume

	      -u print the UUID of the subvolume

	      -o print only subvolumes bellow specified <path>.

	      -r only readonly subvolumes in the filesystem will be listed.

	      -s only snapshot subvolumes in the filesystem will be listed.

	      -G [+|-]value list subvolumes in the filesystem that its genera‐
	      tion is >=, <= or = value. '+' means  >=	value,	'-'  means  <=
	      value, If there is neither '+' nor '-', it means = value.

	      -C [+|-]value list subvolumes in the filesystem that its ogener‐
	      ation is >=, <= or = value.  The	usage  is  the	same  to  '-g'
	      option.

	      --sort=rootid,gen,ogen,path  list	 subvolumes in order by speci‐
	      fied items.  you can add '+' or '-' in front of each items,  '+'
	      means ascending, '-' means descending. The default is ascending.

	      for --sort you can combine some items together by ',', just like
	      -sort=+ogen,-gen,path,rootid.

       subvolume set-default <id> <path>
	      Set the subvolume of the filesystem <path> which is  mounted  as
	      default.	The subvolume is identified by <id>, which is returned
	      by the subvolume list command.

       subvolume get-default <path>
	      Get the default subvolume of the filesystem <path>.  The	output
	      format is similar to subvolume list command.

       subvolume find-new <subvolume> <last_gen>
	      List   the   recently  modified  files  in  a  subvolume,	 after
	      <last_gen> ID.

       subvolume show <path>
	      Show information of a given subvolume in the <path>.

       filesystem defragment -c[zlib|lzo] [-l len] [-s start] [-t size]	 -[vf]
       <file>|<dir> [<file>|<dir>...]

	      Defragment  file	data  and/or directory metadata. To defragment
	      all files in a directory you have to specify each one on its own
	      or use your shell wildcards.

	      The  start position and the number of bytes to defragment can be
	      specified by start and len. Any  extent  bigger  than  threshold
	      will  be	considered already defragged. Use 0 to take the kernel
	      default, and use 1 to say every single extent must be rewritten.
	      You can also turn on compression in defragment operations.

	      -v be verbose

	      -c compress file contents while defragmenting

	      -f flush filesystem after defragmenting

	      -s start defragment only from byte start onward

	      -l len defragment only up to len bytes

	      -t size defragment only files at least size bytes big

	      For  start,  len,	 size it is possible to append a suffix like k
	      for 1 KBytes, m for 1 MBytes...

	      NOTE: defragmenting with kernels up to 2.6.37 will unlink COW-ed
	      copies  of  data,	 don't	use  it if you use snapshots, have de-
	      duplicated your data or made copies with cp --reflink.

       filesystem sync <path>
	      Force a sync for the filesystem identified by <path>.

       filesystem resize [devid:][+/-]<size>[gkm]|[devid:]max <path>
	      Resize a filesystem identified  by  <path>  for  the  underlying
	      device devid.  The devid can be found with btrfs filesystem show
	      and defaults to 1 if not specified.  The <size> parameter speci‐
	      fies  the	 new  size of the filesystem.  If the prefix + or - is
	      present the size is  increased  or  decreased  by	 the  quantity
	      <size>.	If  no	units  are  specified,	the unit of the <size>
	      parameter defaults to bytes. Optionally, the size parameter  may
	      be suffixed by one of the following units designators: 'K', 'M',
	      or 'G', kilobytes, megabytes, or gigabytes, respectively.

	      If 'max' is passed, the filesystem  will	occupy	all  available
	      space on the device devid.

	      The  resize  command  does not manipulate the size of underlying
	      partition.  If you wish to enlarge/reduce a filesystem, you must
	      make  sure  you  can  expand  the partition before enlarging the
	      filesystem and shrink the partition after reducing the  size  of
	      the  filesystem.	 This  can done using fdisk(8) or parted(8) to
	      delete the existing partition  and  recreate  it	with  the  new
	      desired  size.   When  recreating the partition make sure to use
	      the same starting disk cylinder as before.

       filesystem label <dev> [newlabel]
	      Show or update the label of a filesystem. <dev> is used to iden‐
	      tify the filesystem.  If a newlabel optional argument is passed,
	      the label is changed. The	 following  constraints	 exist	for  a
	      label:

	      -	 the  maximum allowable length shall be less or equal than 256
	      chars

	      - the label shall not  contain the '/' or '\' characters.

	      NOTE: Currently there are the following limitations:

	      - the filesystem has to be unmounted

	      - the filesystem should not have more than one device.

       filesystem show [--all-devices|<uuid>|<label>]
	      Show the btrfs filesystem with some additional info. If no  UUID
	      or label is passed, btrfs show info of all the btrfs filesystem.
	      If --all-devices is passed,  all	the  devices  under  /dev  are
	      scanned;	otherwise  the	devices	 list  is  extracted  from the
	      /proc/partitions file.

       filesystem balance <path>
	      Balance the chunks of the filesystem identified by <path> across
	      the devices.

       device stats [-z] {<path>|<device>}
	      Read  and	 print	the  device  IO	 stats	for all devices of the
	      filesystem identified by <path> or for a single <device>.

	      Options

	      -z     Reset stats to zero after reading them.

       device add <dev> [<dev>..] <path>
	      Add device(s) to the filesystem identified by <path>.

       device delete <dev> [<dev>..] <path>
	      Remove device(s) from a filesystem identified by <path>.

       device scan [--all-devices|<device> [<device>...]
	      If one or more devices are passed, these are scanned for a btrfs
	      filesystem.  If no devices are passed, btrfs scans all the block
	      devices listed in the /proc/partitions file.  Finally, if --all-
	      devices is passed, all the devices under /dev are scanned.

       replace start [-Bfr] <srcdev>|<devid> <targetdev> <path>
	      Replace  device  of  a  btrfs filesystem.	 On a live filesystem,
	      duplicate the data to  the  target  device  which	 is  currently
	      stored  on the source device. If the source device is not avail‐
	      able anymore, or if the -r option is set, the data is built only
	      using  the  RAID	redundancy mechanisms. After completion of the
	      operation, the source device is removed from the filesystem.  If
	      the  srcdev is a numerical value, it is assumed to be the device
	      id of the filesystem which is mounted at mount_point,  otherwise
	      is  is  the  path	 to the source device. If the source device is
	      disconnected, from the system, you have to use the devid parame‐
	      ter  format.  The targetdev needs to be same size or larger than
	      the srcdev.

	      Options

	      -r     only read from srcdev  if	no  other  zero-defect	mirror
		     exists  (enable  this  if	your  drive  has  lots of read
		     errors, the access would be very slow)

	      -f     force using and overwriting targetdev even	 if  it	 looks
		     like   containing	a  valid  btrfs	 filesystem.  A	 valid
		     filesystem is assumed if  a  btrfs	 superblock  is	 found
		     which contains a correct checksum. Devices which are cur‐
		     rently mounted are never allowed to be used as  the  tar‐
		     getdev

	      -B     do not background

       replace status [-1] <path>
	      Print  status  and  progress  information	 of  a	running device
	      replace operation.

	      Options

	      -1     print once instead of print continously until the replace
		     operation finishes (or is canceled)

       replace cancel <path>
	      Cancel a running device replace operation.

       scrub start [-Bdqru] {<path>|<device>}
	      Start  a	scrub  on  all devices of the filesystem identified by
	      <path> or on  a  single  <device>.  Without  options,  scrub  is
	      started  as  a background process. Progress can be obtained with
	      the scrub status command. Scrubbing involves  reading  all  data
	      from  all	 disks	and  verifying checksums. Errors are corrected
	      along the way if possible.

	      Options

	      -B   Do not background and print scrub statistics when finished.

	      -d   Print separate statistics for each device of the filesystem
		   (-B only).

	      -q   Quiet. Omit error messages and statistics.

	      -r   Read only mode. Do not attempt to correct anything.

	      -u   Scrub unused space as well. (NOT IMPLEMENTED)

       scrub cancel {<path>|<device>}
	      If  a  scrub  is running on the filesystem identified by <path>,
	      cancel it.  Progress is saved in the  scrub  progress  file  and
	      scrubbing	 can  be resumed later using the scrub resume command.
	      If a <device> is given, the corresponding	 filesystem  is	 found
	      and scrub cancel behaves as if it was called on that filesystem.

       scrub resume [-Bdqru] {<path>|<device>}
	      Resume  a	 canceled or interrupted scrub cycle on the filesystem
	      identified by <path> or on a given <device>. Does	 not  start  a
	      new scrub if the last scrub finished successfully.

	      Options

	      see scrub start.

       scrub status [-d] {<path>|<device>}
	      Show  status of a running scrub for the filesystem identified by
	      <path> or for the specified <device>.  If no scrub  is  running,
	      show  statistics of the last finished or canceled scrub for that
	      filesystem or device.

	      Options

	      -d   Print separate statistics for each device of	 the  filesys‐
		   tem.

       inspect-internal inode-resolve [-v] <inode> <path>
	      Resolves an <inode> in subvolume <path> to all filesystem paths.

	      Options

	      -v   verbose  mode.  print  count	 of returned paths and ioctl()
		   return value

       inspect-internal logical-resolve [-Pv] [-s bufsize] <logical> <path>
	      Resolves a <logical> address in the filesystem mounted at <path>
	      to  all  inodes.	 By  default, each inode is then resolved to a
	      file system path (similar to the inode-resolve subcommand).

	      Options

	      -P   skip the path resolving and print the inodes instead

	      -v   verbose mode. print count of returned paths and all ioctl()
		   return values

	      -s   set	inode container's size. This is used to increase inode
		   container's size in case it is not enough to read  all  the
		   resolved results. The max value one can set is 64k.

EXIT STATUS
       btrfs  returns a zero exist status if it succeeds. Non zero is returned
       in case of failure.

AVAILABILITY
       btrfs is part of btrfs-progs. Btrfs filesystem is currently under heavy
       development,  and not suitable for any uses other than benchmarking and
       review.	Please refer to the  btrfs  wiki  http://btrfs.wiki.kernel.org
       for further details.

SEE ALSO
       mkfs.btrfs(8)

btrfs								      BTRFS(8)
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