Arch manual pages


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

btrfs qgroup <subcommand> <args>









The qgroup hierarchy is built by commands create and assign.






(default since: 4.19) Automatically schedule quota rescan if the new qgroup assignment would lead to quota inconsistency. See QUOTA RESCAN for more information.


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.


destroy <qgroupid> <path>

Destroy a qgroup.









limit space exclusively assigned to this qgroup.

remove <src> <dst> <path>



The same as assign subcommand.

show [options] <path>




print parent qgroup id.


print child qgroup id.


print limit of referenced size of qgroup.


print limit of exclusive size of qgroup.






raw numbers in bytes, without the B suffix.


print human friendly numbers, base 1024, this is the default






show sizes in KiB, or kB with --si.


show sizes in MiB, or MB with --si.


show sizes in GiB, or GB with --si.


show sizes in TiB, or TB with --si.


list qgroups in order of <attr>.






The rescan reads all extent sharing metadata and updates the respective qgoups 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.



12/03/2019 Btrfs v5.4