btrfs-qgroup <root
BTRFS-QGROUP(8)                            Btrfs Manual                           BTRFS-QGROUP(8)

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

SYNOPSIS
       btrfs qgroup  

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/ is created again.

SUBCOMMAND
       assign [options]   
           Assign qgroup  as the child qgroup of  in the btrfs filesystem identified by
           .

           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  
           Create a subvolume quota group.

           For the 0/ qgroup, a qgroup can be created even before the subvolume
           created.

       destroy  
           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] |none [] 
           Limit the size of a qgroup to  or no limit in the btrfs filesystem identified by
           .

           If  is not given, qgroup of the subvolume identified by  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   
           Remove the relationship between child qgroup  and parent qgroup  in the
           btrfs filesystem identified by .

       show [options] 
           Show all qgroups in the btrfs filesystem identified by .

           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=[+/-][,[+/-]]...
               list qgroups in order of .

                can be one or more of qgroupid,rfer,excl,max_rfer,max_excl.

               Prefix '+' means ascending order and '-' means descending order of . If no
               prefix is given, use ascending order by default.

               If multiple 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),

Btrfs v4.4                                  01/19/2016                            BTRFS-QGROUP(8)

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