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.

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),

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