btrfs-qgroup (8)
Leading comments
Title: btrfs-qgroup
Author: [FIXME: author] [see http://docbook.sf.net/el/author]
Generator: DocBook XSL Stylesheets v1.79.0 <http://docbook.sf.net/>
Date: 07/28/2017
Manual: Btrfs Manual
Source: Btrfs v4.12
Language: English
NAME
btrfs-qgroup - control the quota group of a btrfs filesystemSYNOPSIS
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 limit sare 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 cancqt 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.
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 m[blue]btrfs.wiki.kernel.orgm[] for further details.