Manpage/btrfs-subvolume

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(Update from git, v4.7+)
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==NAME==
 
==NAME==
btrfs-subvolume - control btrfs subvolume(s)
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btrfs-subvolume - manage btrfs subvolumes
  
 
==SYNOPSIS==
 
==SYNOPSIS==
Line 11: Line 11:
 
==DESCRIPTION==
 
==DESCRIPTION==
  
<p><b>btrfs subvolume</b> is used to control the filesystem to create/delete/list/show
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<p><b>btrfs subvolume</b> is used to create/delete/list/show btrfs subvolumes and
subvolumes and snapshots.</p>
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snapshots.</p>
 
==SUBVOLUME AND SNAPSHOT==
 
==SUBVOLUME AND SNAPSHOT==
  
<p>A subvolume in btrfs is not like an LVM logical volume, which is quite
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<p>A subvolume is a part of filesystem with it&#8217;s own and independent
independent from each other, a btrfs subvolume has its hierarchy and relations
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file/directory hierarchy. Subvolumes can share file extents. A snapshot is
between other subvolumes.</p>
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also subvolume, but with a given initial content of the original subvolume.</p>
<p>A subvolume in btrfs can be accessed in two ways.</p>
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<blockquote><b>Note:</b>
<ol>
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A subvolume in btrfs is not like an LVM logical volume, which is
 +
block-level snapshot while btrfs subvolumes are file extent-based.</blockquote>
 +
<p>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.</p>
 +
<p>A subvolume in btrfs can be accessed in two ways:</p>
 +
<ul>
 
<li>
 
<li>
 
<p>
 
<p>
From the parent subvolume<br/>
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like any other directory that is accessible to the user
When accessing from the parent subvolume, the subvolume can be used just
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like a directory. It can have child subvolumes and its own files/directories.
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</p>
 
</p>
 
</li>
 
</li>
 
<li>
 
<li>
 
<p>
 
<p>
Separate mounted filesystem<br/>
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like a separately mounted filesystem (options <em>subvol</em> or <em>subvolid</em>)
When [http://man7.org/linux/man-pages/man8/mount.8.html mount(8)] using <em>subvol</em> or <em>subvolid</em> mount option, one can access
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files/directories/subvolumes inside it, but nothing in parent subvolumes.
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</p>
 
</p>
 
</li>
 
</li>
</ol>
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</ul>
<p>Also every btrfs filesystem has a default subvolume as its initially top-level
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<p>In the latter case the parent directory is not visible and accessible. This is
subvolume, whose subvolume id is 5. (0 is also acceptable as an alias.)</p>
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similar to a bind mount, and in fact the subvolume mount does exactly that.</p>
<p>A btrfs snapshot is much like a subvolume, but shares its data(and metadata)
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<p>A freshly created filesystem is also a subvolume, called <em>top-level</em>,
with other subvolume/snapshot. Due to the capabilities of COW, modifications
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internally has an id 5. This subvolume cannot be removed or replaced by another
inside a snapshot will only show in a snapshot but not in its source subvolume.</p>
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subvolume. This is also the subvolume that will be mounted by default, unless
<p>Although in btrfs, subvolumes/snapshots are treated as directories, only
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the default subvolume has been changed (see subcommand <em>set-default</em>).</p>
subvolume/snapshot can be the source of a snapshot, snapshot can not be made
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<p>A snapshot is a subvolume like any other, with given initial content. By
from normal directories.</p>
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default, snapshots are created read-write. File modifications in a snapshot
 +
do not affect the files in the original subvolume.</p>
 
==SUBCOMMAND==
 
==SUBCOMMAND==
  
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<p>[[Manpage/mkfs.btrfs|mkfs.btrfs(8)]],
 
<p>[[Manpage/mkfs.btrfs|mkfs.btrfs(8)]],
 +
[http://man7.org/linux/man-pages/man8/mount.8.html mount(8)],
 
[[Manpage/btrfs-quota|btrfs-quota(8)]],
 
[[Manpage/btrfs-quota|btrfs-quota(8)]],
 
[[Manpage/btrfs-qgroup|btrfs-qgroup(8)]],</p>
 
[[Manpage/btrfs-qgroup|btrfs-qgroup(8)]],</p>
 
[[Category:Manpage]]
 
[[Category:Manpage]]

Revision as of 17:45, 18 August 2016

Contents

btrfs-subvolume(8) manual page

Note: manual pages are located at read-the-docs site, please update your links.



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),

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