btrfs-progs/Documentation/btrfs-qgroup.asciidoc

btrfs-qgroup(8)
===============

NAME
----
btrfs-qgroup - control the quota group of a btrfs filesystem

SYNOPSIS
--------
*btrfs qgroup* <subcommand> <args>

DESCRIPTION
-----------
*btrfs qgroup* is used to control quota group (qgroup) of a btrfs filesystem.

NOTE: To use qgroup you need to enable quota first using *btrfs quota enable*
command.

WARNING: Qgroup is not stable yet and will impact performance in current mainline
kernel (v3.14 so far).

QGROUP
------
Quota groups or qgroup in btrfs make a tree hierarchy, the leaf qgroups are
attached to subvolumes. The size limits are set per qgroup and apply when any
limit is reached in tree that contains a given subvolume.

The limits are separated between shared and exclusive and reflect the extent
ownership. For example a fresh snapshot shares almost all the blocks with the
original subvolume, new writes to either subvolume will raise towards the
exclusive limit.

The qgroup identifiers conform to 'level/id' where level 0 is reserved to the
qgroups associated with subvolumes. Such qgroups are created automatically.

The qgroup hierarchy is built by commands *create* and *assign*.

NOTE: If the qgroup of a subvolume is destroyed, quota about the subvolume
will not be functional until qgroup '0/<subvolume id>' is created again.

SUBCOMMAND
----------
*assign* [options] <src> <dst> <path>::
Assign qgroup <src> as the child qgroup of <dst> in the btrfs filesystem
identified by <path>.
+
`Options`
+
--rescan::::
Automatically schedule quota rescan if the new qgroup assignment leads to
quota inconsistency.
--no-rescan::::
Explicitly ask not to do a rescan.

*create* <qgroupid> <path>::
Create a subvolume quota group.
+
For the '0/<subvolume id>' qgroup, a qgroup can be created even before the
subvolume created.

*destroy* <qgroupid> <path>::
Destroy a qgroup.
+
If a qgroup is no isolated,which means it is a parent or child qgroup, it
can't be destroyed.

*limit* [options] <size>|none [<qgroupid>] <path>::
Limit the size of a qgroup to <size> or no limit in the btrfs filesystem
identified by <path>.
+
If <qgroupid> is not given, qgroup of the subvolume identified by <path>
is used if possible.
+
`Options`
+
-c::::
limit amount of data after compression. This is the default, it is currently not
possible to turn off this option.
+
-e::::
limit space exclusively assigned to this qgroup.

*remove* <src> <dst> <path>::
Remove the relationship between child qgroup <src> and parent qgroup <dst> in
the btrfs filesystem identified by <path>.

*show* [options] <path>::
Show all qgroups in the btrfs filesystem identified by <path>.
+
`Options`
+
-p::::
print parent qgroup id.
-c::::
print child qgroup id.
-r::::
print limit of referenced size of qgroup.
-e::::
print limit of exclusive size of qgroup.
-F::::
list all qgroups which impact the given path(include ancestral qgroups)
-f::::
list all qgroups which impact the given path(exclude ancestral qgroups)
--raw::::
raw numbers in bytes, without the 'B' suffix.
--human-readable::::
print human friendly numbers, base 1024, this is the default
--iec::::
select the 1024 base for the following options, according to the IEC standard.
--si::::
select the 1000 base for the following options, according to the SI standard.
--kbytes::::
show sizes in KiB, or kB with --si.
--mbytes::::
show sizes in MiB, or MB with --si.
--gbytes::::
show sizes in GiB, or GB with --si.
--tbytes::::
show sizes in TiB, or TB with --si.
--sort=[\+/-]<attr>[,[+/-]<attr>]...::::
list qgroups in order of <attr>.
+
<attr> can be one or more of qgroupid,rfer,excl,max_rfer,max_excl.
+
Prefix \'+' means ascending order and \'-' means descending order of <attr>.
If no prefix is given, use ascending order by default.
+
If multiple <attr>s is given, use comma to separate.
+
--sync::::
To retrieve information after updating the state of qgroups,
force sync of the filesystem identified by <path> before getting information.

EXIT STATUS
-----------
*btrfs qgroup* returns a zero exit status if it succeeds. Non zero 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),
`btrfs-subvolume`(8),
`btrfs-quota`(8),