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NAME | SYNOPSIS | DESCRIPTION | SUBVOLUME AND SNAPSHOT | SUBCOMMAND | SUBVOLUME FLAGS | EXAMPLES | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON |
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BTRFS-SUBVOLUME(8) Btrfs Manual BTRFS-SUBVOLUME(8)
btrfs-subvolume - manage btrfs subvolumes
btrfs subvolume <subcommand> [<args>]
btrfs subvolume is used to create/delete/list/show btrfs
subvolumes and snapshots.
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 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.
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)
The subvolume flag currently implemented is the ro property.
Read-write subvolumes have that set to false, snapshots as true.
In addition to that, a plain snapshot will also have last change
generation and creation generation equal.
Read-only snapshots are building blocks fo incremental send (see
btrfs-send(8)) and the whole use case relies on unmodified
snapshots where the relative changes are generated from. Thus,
changing the subvolume flags from read-only to read-write will
break the assumptions and may lead to unexpected changes in the
resulting incremental stream.
A snapshot that was created by send/receive will be read-only,
with different last change generation, read-only and with set
received_uuid which identifies the subvolume on the filesystem
that produced the stream. The usecase relies on matching data on
both sides. Changing the subvolume to read-write after it has
been received requires to reset the received_uuid. As this is a
notable change and could potentially break the incremental send
use case, performing it by btrfs property set requires force if
that is really desired by user.
Note
The safety checks have been implemented in 5.14.2, any
subvolumes previously received (with a valid received_uuid)
and read-write status may exist and could still lead to
problems with send/receive. You can use btrfs subvolume show
to identify them. Flipping the flags to read-only and back to
read-write will reset the received_uuid manually. There may
exist a convenience tool in the future.
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
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.
mkfs.btrfs(8), mount(8), btrfs-quota(8), btrfs-qgroup(8),
btrfs-send(8)
This page is part of the btrfs-progs (btrfs filesystem tools)
project. Information about the project can be found at
⟨https://btrfs.wiki.kernel.org/index.php/Btrfs_source_repositories⟩.
If you have a bug report for this manual page, see
⟨https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#How_do_I_report_bugs_and_issues.3F⟩.
This page was obtained from the project's upstream Git repository
⟨git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git⟩
on 2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-02.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
Btrfs v5.16.1 02/06/2022 BTRFS-SUBVOLUME(8)
Pages that refer to this page: tmpfiles.d(5), btrfs(8), btrfs-filesystem(8), btrfs-property(8), btrfs-qgroup(8), btrfs-quota(8), btrfs-send(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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