Provided by: btrfs-tools_3.12-1ubuntu0.2_amd64 
NAME
btrfs - control a btrfs filesystem
SYNOPSIS
btrfs subvolume create [-i <qgroupid>] [<dest>/]<name>
btrfs subvolume delete <subvolume> [<subvolume>...]
btrfs subvolume list [options] [-G [+|-]value] [-C [+|-]value]
[--sort=rootid,gen,ogen,path] <path>
btrfs subvolume snapshot [-r] <source> <dest>|[<dest>/]<name>
btrfs subvolume get-default <path>
btrfs subvolume set-default <id> <path>
btrfs subvolume find-new <subvolume> <lastgen>
btrfs subvolume show <path>
btrfs filesystem df <path>
btrfs filesystem show [--mounted|--all-devices|<uuid>]
btrfs filesystem sync <path>
btrfs filesystem defragment [options] <file>|<dir> [<file>|<dir>...]
btrfs filesystem resize [devid:][+/-]<size>[gkm]|[devid:]max <path>
btrfs filesystem label [<device>|<mount_point>] [<newlabel>]
btrfs [filesystem] balance start [options] <path>
btrfs [filesystem] balance pause <path>
btrfs [filesystem] balance cancel <path>
btrfs [filesystem] balance resume <path>
btrfs [filesystem] balance status [-v] <path>
btrfs device add [-Kf] <device> [<device>...] <path>
btrfs device delete <device> [<device>...] <path>
btrfs device scan [--all-devices|<device> P[<device>...]
btrfs device ready <device>
btrfs device stats [-z] {<path>|<device>}
btrfs scrub start [-BdqrR] [-c ioprio_class -n ioprio_classdata] {<path>|<device>}
btrfs scrub cancel {<path>|<device>}
btrfs scrub resume [-BdqrR] [-c ioprio_class -n ioprio_classdata] {<path>|<device>}
btrfs scrub status [-d] {<path>|<device>}
btrfs check [options] <device>
btrfs rescue chunk-recover [options] <path>
btrfs rescue super-recover [options] <path>
btrfs restore [options] <device>
btrfs inspect-internal inode-resolve [-v] <inode> <path>
btrfs inspect-internal logical-resolve [-Pv] [-s <size>] <logical> <path>
btrfs inspect-internal subvolid-resolve <subvolid> <path>
btrfs inspect-internal rootid <path>
btrfs send [-v] [-p <parent>] [-c <clone-src>] [-f <outfile>] <subvol>
btrfs receive [-ve] [-f <infile>] <mount>
btrfs quota enable <path>
btrfs quota disable <path>
btrfs quota rescan [-s] <path>
btrfs qgroup assign <src> <dst> <path>
btrfs qgroup remove <src> <dst> <path>
btrfs qgroup create <qgroupid> <path>
btrfs qgroup destroy <qgroupid> <path>
btrfs qgroup show <path>
btrfs qgroup limit [options] <size>|none [<qgroupid>] <path>
btrfs replace start [-Bfr] <srcdev>|<devid> <targetdev> <mount_point>
btrfs replace status [-1] <mount_point>
btrfs replace cancel <mount_point>
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 terminated 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* commands.
COMMANDS
subvolume create [-i <qgroupid>] [<dest>/]<name>
Create a subvolume <name> in <dest>. If <dest> is not given subvolume <name> will
be created in the current directory.
Options
-i <qgroupid>
Add the newly created subvolume to a qgroup. This option can be given multiple
times.
subvolume delete <subvolume> [<subvolume>...]
Delete the subvolume <subvolume>. If <subvolume> is not a subvolume, btrfs returns
an error.
subvolume list [options] [-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 command, 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.
Options
-p print parent ID.
-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 origin generation.
-g print the generation of the subvolume.
-o print only subvolumes bellow specified <path>.
-u print the UUID of the subvolume.
-q print the parent uuid of subvolumes (and snapshots).
-t print the result as a table.
-s only snapshot subvolumes in the filesystem will be listed.
-r only readonly subvolumes in the filesystem will be listed.
-G [+|-]value
list subvolumes in the filesystem that its generation is >=, <= or = value.
'+' means >= value, '-' means <= value, If there is neither '+' nor '-', it
means = value.
-C [+|-]value
list subvolumes in the filesystem that its ogeneration is >=, <= or = value.
The usage is the same to '-g' option.
--sort=rootid,gen,ogen,path
list subvolumes in order by specified 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 snapshot [-r] <source> <dest>|[<dest>/]<name>
Create a writable/readonly snapshot of the subvolume <source> with the name <name>
in the <dest> directory. If only <dest> is given, the subvolume will be named the
basename of <source>. If <source> is not a subvolume, btrfs returns an error. If
-r is given, the snapshot will be readonly.
subvolume get-default <path>
Get the default subvolume of the filesystem <path>. The output format is similar to
subvolume list command.
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 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 df <path>
Show space usage information for a mount point.
filesystem show [--mounted|--all-devices|<uuid>]
Show the btrfs filesystem with some additional info. If no option or UUID is
passed, btrfs shows information of all the btrfs filesystem both mounted and
unmounted. If --mounted is passed, it would probe btrfs kernel to list mounted
btrfs filesystem(s); If --all-devices is passed, all the devices under /dev are
scanned; otherwise the devices list is extracted from the /proc/partitions file.
filesystem sync <path>
Force a sync for the filesystem identified by <path>.
filesystem defragment [options] <file>|<dir> [<file>|<dir>...]
Defragment file data and/or directory metadata. If -r is passed, files in dir will
be defragmented recursively.
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.
Options
-v be verbose
-c compress file contents while defragmenting
-r defragment files recursively
-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 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 specifies 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>|<mount_point>] [newlabel]
Show or update the label of a filesystem. [<device>|<mountpoint>] is used to
identify 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 than 256 chars
[filesystem] balance start [options] <path>
Balance chunks across the devices Balance and/or convert (change allocation profile
of) chunks that passed all filters in a comma-separated list of filters for a
particular chunk type. If filter list is not given balance all chunks of that
type. In case none of the -d, -m or -s options is given balance all chunks in a
filesystem.
Options
-d[filters]
act on data chunks
-m[filters]
act on metadata chunks
-s[filters]
act on system chunks (only under -f)
-v be verbose
-f force reducing of metadata integrity
[filesystem] balance pause <path>
Pause running balance.
[filesystem] balance cancel <path>
Cancel running or paused balance.
[filesystem] balance resume <path>
Resume interrupted balance.
[filesystem] balance status [-v] <path>
Show status of running or paused balance.
Options
-v be verbose
device add [-Kf] <dev> [<dev>...] <path>
Add device(s) to the filesystem identified by <path>. If applicable, a whole
device discard (TRIM) operation is performed.
Options
-K|--nodiscard
do not perform discard by default
-f|--force
force overwrite of existing filesystem on the given disk(s)
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 uses block devices containing btrfs filesystem as listed
by blkid. Finally, if --all-devices is passed, all the devices under /dev are
scanned.
device ready <device>
Check device to see if it has all of it's devices in cache for mounting.
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.
scrub start [-BdqrR] [-c ioprio_class -n ioprio_classdata] {<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.
The default IO priority of scrub is the idle class. The priority can be configured
similar to the ionice(1) syntax.
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.
-R Raw print mode. Print full data instead of summary.
-c ioprio_class
Set IO priority class (see ionice(1) manpage).
-n ioprio_classdata
Set IO priority classdata (see ionice(1) manpage).
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 [-BdqrR] [-c ioprio_class -n ioprio_classdata] {<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 filesystem.
check [options] <device>
Check an unmounted btrfs filesystem.
Options
-s|--support <superblock>
use this superblock copy.
--repair
try to repair the filesystem.
--init-csum-tree
create a new CRC tree.
--init-extent-tree
create a new extent tree.
rescue chunk-recover [options] <device>
Recover the chunk tree by scanning the devices one by one.
Options
-y assume an answer of 'yes' to all questions.
-v verbose mode.
-h help.
rescue super-recover [options] <device>
Recover bad superblocks from good copies.
Options
-y assume an answer of 'yes' to all questions.
-v verbose mode.
restore [options] <device>
Try to restore files from a damaged filesystem(unmounted).
Options
-s get snapshots.
-x get extended attributes.
-v verbose.
-i ignore errors.
-o overwrite.
-t <location>
tree location.
-f <offset>
filesystem location.
-u <block>
super mirror.
-r <rootid>
root objectid.
-d find dir.
-l list tree roots.
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 <bufsize>
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.
inspect-internal subvolid-resolve <subvolid> <path>
Get file system paths for the given subvolume ID.
inspect-internal rootid <path>
For a given file or directory, return the containing tree root id. For a subvolume
return it's own tree id.
The result is undefined for the so-called empty subvolumes (identified by inode
number 2).
send [-v] [-p <parent>] [-c <clone-src>] [-f <outfile>] <subvol>
Send the subvolume to stdout. Sends the subvolume specified by <subvol> to stdout.
By default, this will send the whole subvolume. To do an incremental send, use '-p
<parent>'. If you want to allow btrfs to clone from any additional local snapshots,
use '-c <clone-src>' (multiple times where applicable). You must not specify clone
sources unless you guarantee that these snapshots are exactly in the same state on
both sides, the sender and the receiver. It is allowed to omit the which case
'btrfs send' will determine a suitable parent among the clone sources itself.
Options
-v Enable verbose debug output. Each occurrence of this option increases the
verbose level more.
-p <parent>
Send an incremental stream from <parent> to <subvol>.
-c <clone-src>
Use this snapshot as a clone source for an incremental send (multiple
allowed).
-f <outfile>
Output is normally written to stdout. To write to a file, use this option. An
alternative would be to use pipes.
receive [-ve] [-f <infile>] <mount>
Receive subvolumes from stdin. Receives one or more subvolumes that were
previously sent with btrfs send. The received subvolumes are stored into <mount>.
btrfs receive will fail in case a receiving subvolume already exists. It will also
fail in case a previously received subvolume was changed after it was received.
After receiving a subvolume, it is immediately set to read only.
Options
-v Enable verbose debug output. Each occurrence of this option increases the
verbose level more.
-f <infile>
By default, btrfs receive uses stdin to receive the subvolumes. Use this
option to specify a file to use instead.
-e Terminate after receiving an <end cmd> in the data stream. Without this
option, the receiver terminates only if an error is recognized or on EOF.
quota enable <path>
Enable subvolume quota support for a filesystem.
quota disable <path>
Disable subvolume quota support for a filesystem.
quota rescan [-s] <path>
Trash all qgroup numbers and scan the metadata again with the current config.
Options
-s show status of a running rescan operation.
qgroup assign <src> <dst> <path>
Enable subvolume qgroup support for a filesystem.
qgroup remove <src> <dst> <path>
Remove a subvol from a quota group.
qgroup create <qgroupid> <path>
Create a subvolume quota group.
qgroup destroy <qgroupid> <path>
Destroy a subvolume quota group.
qgroup show <path>
Show all subvolume quota groups.
qgroup limit [options] <size>|none [<qgroupid>] <path>
Limit the size of a subvolume quota group.
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 available 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 parameter 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 currently mounted
are never allowed to be used as the <targetdev>
-B do not background
replace status [-1] <mount_point>
Print status and progress information of a running device replace operation.
Options
-1 print once instead of print continuously until the replace operation finishes
(or is canceled)
replace cancel <mount_point>
Cancel a running device replace operation.
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-tools. 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), ionice(1)