btrfs-subvolume(8)
NAME
btrfs-subvolume - manage btrfs subvolumes
SYNOPSIS
btrfs subvolume <subcommand> [<args>]
DESCRIPTION
btrfs subvolume is used to create/delete/list/show btrfs subvolumes and
snapshots.
SUBVOLUME AND SNAPSHOT
A subvolume is a part of filesystem with it's own and independent
file/directory hierarchy. Subvolumes can share file extents. A snapshot
is also subvolume, but with a given initial content of the original
subvolume.
Note
A subvolume in btrfs is not like an LVM logical volume, which is
block-level snapshot while btrfs subvolumes are file extent-based.
A subvolume looks like a normal directory, with some additional
operations described below. Subvolumes can be renamed or moved, nesting
subvolumes is not restricted but has some implications regarding
snapshotting.
A subvolume in btrfs can be accessed in two ways:
* like any other directory that is accessible to the user
* like a separately mounted filesystem (options subvol or subvolid)
In the latter case the parent directory is not visible and accessible.
This is similar to a bind mount, and in fact the subvolume mount does
exactly that.
A freshly created filesystem is also a subvolume, called top-level,
internally has an id 5. This subvolume cannot be removed or replaced by
another subvolume. This is also the subvolume that will be mounted by
default, unless the default subvolume has been changed (see subcommand
set-default).
A snapshot is a subvolume like any other, with given initial content.
By default, snapshots are created read-write. File modifications in a
snapshot do not affect the files in the original subvolume.
SUBCOMMAND
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.
delete [options] <subvolume> [<subvolume>...]
Delete the subvolume(s) from the filesystem.
If <subvolume> is not a subvolume, btrfs returns an error but
continues if there are more arguments to process.
The corresponding directory is removed instantly but the data
blocks are removed later. The deletion does not involve full commit
by default due to performance reasons (as a consequence, the
subvolume may appear again after a crash). Use one of the --commit
options to wait until the operation is safely stored on the media.
Options
-c|--commit-after
wait for transaction commit at the end of the operation
-C|--commit-each
wait for transaction commit after deleting each subvolume
find-new <subvolume> <last_gen>
List the recently modified files in a subvolume, after <last_gen>
ID.
get-default <path>
Get the default subvolume of the filesystem <path>.
The output format is similar to subvolume list command.
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 below specified <path>.
-u
print the UUID of the subvolume.
-q
print the parent uuid of subvolumes (and snapshots).
-R
print the UUID of the sent subvolume, where the subvolume is
the result of a receive operation
-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.
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.
show <path>
Show information of a given subvolume in the <path>.
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.
sync <path> [subvolid...]
Wait until given subvolume(s) are completely removed from the
filesystem after deletion. If no subvolume id is given, wait until
all current deletion requests are completed, but do not wait for
subvolumes deleted meanwhile. The status of subvolume ids is
checked periodically.
Options
-s <N>
sleep N seconds between checks (default: 1)
EXIT STATUS
btrfs subvolume returns a zero exit status if it succeeds. A non-zero
value is returned in case of failure.
AVAILABILITY
btrfs is part of btrfs-progs. Please refer to the btrfs wiki
http://btrfs.wiki.kernel.org for further details.
SEE ALSO
mkfs.btrfs(8), mount(8), btrfs-quota(8), btrfs-qgroup(8),
Free and Open Source Software