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btrfs-subvolume.rst

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btrfs-subvolume(8)

SYNOPSIS

btrfs subvolume <subcommand> [<args>]

DESCRIPTION

:command:`btrfs subvolume` is used to create/delete/list/show btrfs subvolumes and snapshots.

SUBVOLUME AND SNAPSHOT

A subvolume is a part of filesystem with its own 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 :ref:`set-default<man-subvolume-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 [options] [<dest>/]<name> [[<dest2>/]<name2> ...]

Create subvolume(s) at the destination(s).

If dest part of the path is not given, subvolume name will be created in the current directory.

If multiple destinations are given, then the given options are applied to all subvolumes.

If failure happens for any of the destinations, the command would still retry the remaining destinations, but would return 1 to indicate the failure (similar to what :command:`mkdir` would do.

Options

-i <qgroupid> Add the newly created subvolume to a qgroup. This option can be given multiple times.
-p|--parents
Create any missing parent directories for each argument (like :command:`mkdir -p`).
delete [options] [<subvolume> [<subvolume>...]], delete -i|--subvolid <subvolid> <path>

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.

If --subvolid is used, path must point to a btrfs filesystem. See :ref:`btrfs subvolume list<man-subvolume-list>` or :ref:`btrfs inspect-internal rootid<man-inspect-rootid>` how to get the subvolume id.

The corresponding directory is removed instantly but the data blocks are removed later in the background. The command returns immediately. See :ref:`btrfs subvolume sync<man-subvolume-sync>` how to wait until the subvolume gets completely removed.

The deletion does not involve full transaction 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 device.

Deleting subvolume needs sufficient permissions, by default the owner cannot delete it unless it's enabled by a mount option user_subvol_rm_allowed, or deletion is run as root. The default subvolume (see :ref:`btrfs subvolume set-default<man-subvolume-set-default>`) cannot be deleted and returns error (EPERM) and this is logged to the system log. A subvolume that's currently involved in send (see :doc:`btrfs-send`) also cannot be deleted until the send is finished. This is also logged in the system log.

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.
-i|--subvolid <subvolid>
subvolume id to be removed instead of the <path> that should point to the filesystem with the subvolume
-R|--recursive

delete subvolumes beneath each subvolume recursively

This requires either CAP_SYS_ADMIN or the filesystem must be mounted with user_subvol_rm_allowed mount option. In the unprivileged case, subvolumes which cannot be accessed are skipped. The deletion is not atomic.

-v|--verbose
(deprecated) alias for global -v option
find-new <subvolume> <last_gen>
List the recently modified files in a subvolume, after last_gen generation.
get-default <path>

Get the default subvolume of the filesystem path.

The output format is similar to :command:`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 gen generation top level parent_ID path path

where ID is subvolume's (root)id, generation is an internal counter which is updated every transaction, parent_ID is the same as the parent subvolume's id, and 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.

Options

Path filtering:

-o Print only subvolumes below specified <path>. Note that this is not a recursive command, and won't show nested subvolumes under <path>.
-a print all the subvolumes in the filesystem and distinguish between absolute and relative path with respect to the given path.

Field selection:

-p print the parent ID (parent here means the subvolume which contains this subvolume).
-c print the ogeneration of the subvolume, aliases: ogen or origin generation.
-g print the generation of the subvolume (default).
-u print the UUID of the subvolume.
-q print the parent UUID of the subvolume (parent here means subvolume of which this subvolume is a snapshot).
-R print the UUID of the sent subvolume, where the subvolume is the result of a receive operation.

Type filtering:

-s only snapshot subvolumes in the filesystem will be listed.
-r only readonly subvolumes in the filesystem will be listed.
-d list deleted subvolumes that are not yet cleaned.

Other:

-t print the result as a table.

Sorting:

By default the subvolumes will be sorted by subvolume ID ascending.

-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 [<subvolume>|<id> <path>]

Set the default subvolume for the (mounted) filesystem.

Set the default subvolume for the (mounted) filesystem at path. This will hide the top-level subvolume (i.e. the one mounted with subvol=/ or subvolid=5). Takes action on next mount.

There are two ways how to specify the subvolume, by id or by the subvolume path. The id can be obtained from :ref:`btrfs subvolume list<man-subvolume-list>` :ref:`btrfs subvolume show<man-subvolume-show>` or :ref:`btrfs inspect-internal rootid<man-inspect-rootid>`.

show [options] <path>

Show more information about a subvolume (UUIDs, generations, times, flags, related snapshots).

/mnt/btrfs/subvolume
        Name:                   subvolume
        UUID:                   5e076a14-4e42-254d-ac8e-55bebea982d1
        Parent UUID:            -
        Received UUID:          -
        Creation time:          2018-01-01 12:34:56 +0000
        Subvolume ID:           79
        Generation:             2844
        Gen at creation:        2844
        Parent ID:              5
        Top level ID:           5
        Flags:                  -
        Snapshot(s):

Options

-r|--rootid <ID>
show details about subvolume with root ID, looked up in path
-u|--uuid UUID
show details about subvolume with the given UUID, looked up in path
snapshot [-r] [-i <qgroupid>] <source> <dest>|[<dest>/]<name>

Create a 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.

Options

-r Make the new snapshot read only.
-i <qgroupid> Add the newly created subvolume to a qgroup. This option can be given multiple times.
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 in the meantime.

If the filesystem status changes to read-only then the waiting is interrupted.

Options

-s <N> sleep N seconds between checks (default: 1)

EXAMPLES

Deleting a subvolume

If we want to delete a subvolume called foo from a btrfs volume mounted at :file:`/mnt/bar` we could run the following:

btrfs subvolume delete /mnt/bar/foo

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 documentation at https://btrfs.readthedocs.io.

SEE ALSO

:doc:`btrfs-qgroup`, :doc:`btrfs-quota`, :doc:`btrfs-send`, :doc:`mkfs.btrfs`, :manref:`mount(8)`