240 lines
7.8 KiB
ReStructuredText
240 lines
7.8 KiB
ReStructuredText
btrfs-qgroup(8)
|
|
===============
|
|
|
|
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 (v4.14).
|
|
|
|
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
|
|
(default since: 4.19) Automatically schedule quota rescan if the new qgroup
|
|
assignment would lead to quota inconsistency. See *QUOTA RESCAN* for more
|
|
information.
|
|
--no-rescan
|
|
Explicitly ask not to do a rescan, even if the assignment will make the quotas
|
|
inconsistent. This may be useful for repeated calls where the rescan would add
|
|
unnecessary overhead.
|
|
|
|
create <qgroupid> <path>
|
|
Create a subvolume quota group.
|
|
|
|
For the *0/<subvolume id>* qgroup, a qgroup can be created even before the
|
|
subvolume is created.
|
|
|
|
destroy <qgroupid> <path>
|
|
Destroy a qgroup.
|
|
|
|
If a qgroup is not isolated, meaning it is a parent or child qgroup, then it
|
|
can only be destroyed after the relationship is removed.
|
|
|
|
clear-stale <path>
|
|
Clear all stale qgroups whose subvolume does not exist anymore, this is the
|
|
level 0 qgroup like 0/subvolid. Higher level qgroups are not deleted even
|
|
if they don't have any child qgroups.
|
|
|
|
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*.
|
|
|
|
``Options``
|
|
|
|
--rescan
|
|
(default since: 4.19) Automatically schedule quota rescan if the removed qgroup
|
|
relation would lead to quota inconsistency. See *QUOTA RESCAN* for more
|
|
information.
|
|
--no-rescan
|
|
Explicitly ask not to do a rescan, even if the removal will make the quotas
|
|
inconsistent. This may be useful for repeated calls where the rescan would add
|
|
unnecessary overhead.
|
|
|
|
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* values are 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.
|
|
|
|
QUOTA RESCAN
|
|
------------
|
|
|
|
The rescan reads all extent sharing metadata and updates the respective qgroups
|
|
accordingly.
|
|
|
|
The information consists of bytes owned exclusively (*excl*) or shared/referred
|
|
to (*rfer*). There's no explicit information about which extents are shared or
|
|
owned exclusively. This means when qgroup relationship changes, extent owners
|
|
change and qgroup numbers are no longer consistent unless we do a full rescan.
|
|
|
|
However there are cases where we can avoid a full rescan, if a subvolume whose
|
|
*rfer* number equals its *excl* number, which means all bytes are exclusively
|
|
owned, then assigning/removing this subvolume only needs to add/subtract *rfer*
|
|
number from its parent qgroup. This can speed up the rescan.
|
|
|
|
EXAMPLES
|
|
--------
|
|
|
|
Make a parent group that has two quota group children
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Given the following filesystem mounted at `/mnt/my-vault`
|
|
|
|
.. code-block:: none
|
|
|
|
Label: none uuid: 60d2ab3b-941a-4f22-8d1a-315f329797b2
|
|
Total devices 1 FS bytes used 128.00KiB
|
|
devid 1 size 5.00GiB used 536.00MiB path /dev/vdb
|
|
|
|
Enable quota and create subvolumes. Check subvolume ids.
|
|
|
|
.. code-block:: bash
|
|
|
|
$ cd /mnt/my-vault
|
|
$ btrfs quota enable .
|
|
$ btrfs subvolume create a
|
|
$ btrfs subvolume create b
|
|
$ btrfs subvolume list .
|
|
|
|
ID 261 gen 61 top level 5 path a
|
|
ID 262 gen 62 top level 5 path b
|
|
|
|
Create qgroup and set limit to 10MiB.
|
|
|
|
.. code-block:: bash
|
|
|
|
$ btrfs qgroup create 1/100 .
|
|
$ btrfs qgroup limit 10M 1/100 .
|
|
$ btrfs qgroup assign 0/261 1/100 .
|
|
$ btrfs qgroup assign 0/262 1/100 .
|
|
|
|
And check qgroups.
|
|
|
|
.. code-block:: bash
|
|
|
|
$ btrfs qgroup show .
|
|
|
|
qgroupid rfer excl
|
|
-------- ---- ----
|
|
0/5 16.00KiB 16.00KiB
|
|
0/261 16.00KiB 16.00KiB
|
|
0/262 16.00KiB 16.00KiB
|
|
1/100 32.00KiB 32.00KiB
|
|
|
|
|
|
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 documentation at
|
|
`https://btrfs.readthedocs.io <https://btrfs.readthedocs.io>`_.
|
|
|
|
SEE ALSO
|
|
--------
|
|
|
|
:doc:`btrfs-quota(8)<btrfs-quota>`,
|
|
:doc:`btrfs-subvolume(8)<btrfs-subvolume>`,
|
|
:doc:`mkfs.btrfs(8)<mkfs.btrfs>`,
|