btrfs-subvolume(8) manual page
btrfs-subvolume - manage btrfs subvolumes
btrfs subvolume <subcommand> [<args>]
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.
- 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.
- -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.
wait for transaction commit at the end of the operation
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.
print parent ID.
print all the subvolumes in the filesystem and distinguish between absolute and relative path with respect to the given <path>.
print the ogeneration of the subvolume, aliases: ogen or origin generation.
print the generation of the subvolume.
print only subvolumes below specified <path>.
print the UUID of the subvolume.
print the parent uuid of subvolumes (and snapshots).
print the UUID of the sent subvolume, where the subvolume is the result of a receive operation
print the result as a table.
only snapshot subvolumes in the filesystem will be listed.
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.
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.
- -s <N>
sleep N seconds between checks (default: 1)
btrfs subvolume returns a zero exit status if it succeeds. A non-zero value is returned in case of failure.
btrfs is part of btrfs-progs. Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for further details.