BTRFS-SUBVOLUME(8) Btrfs Manual 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 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:
o like any other directory that is accessible to the user
o 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 -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
btrfs subvolume list or btrfs inspect-internal 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 btrfs 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.
The default subvolume (see btrfs 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 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
-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 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 <ID> path <path>
where ID is subvolume's id, gen is an internal counter which is
updated every transaction, top level is the same as 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>.
-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 btrfs subvolume list,
btrfs subvolume show or btrfs inspect-internal 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.
Options
-s <N>
sleep N seconds between checks (default: 1)
EXAMPLES
Example 1. Deleting a subvolume
If we want to delete a subvolume called foo from a btrfs volume mounted
at /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 btrfs wiki
http://btrfs.wiki.kernel.org for further details.
SEE ALSO
mkfs.btrfs(8), mount(8), btrfs-quota(8), btrfs-qgroup(8),
Btrfs v5.10.1 02/05/2021 BTRFS-SUBVOLUME(8)
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