btrfs-filesystem <root
BTRFS-FILESYSTEM(8)                        Btrfs Manual                       BTRFS-FILESYSTEM(8)

NAME
       btrfs-filesystem - command group of btrfs that usually work on the whole filesystem

SYNOPSIS
       btrfs filesystem  

DESCRIPTION
       btrfs filesystem is used to do the whole filesystem level tasks, including all the regular
       filesystem operations like resizing, space stats, label setting/getting, and
       defragmentation.

SUBCOMMAND
       df [options] 
           Show a terse summary information about allocation of block group types of a given
           mount point. The original purpose of this command was a debugging helper. The output
           needs to be further interpreted and is not suitable for quick overview.

           An example with description:

           ·   device size: 1.9TiB, one device, no RAID

           ·   filesystem size: 1.9TiB

           ·   created with: mkfs.btrfs -d single -m single

               $ btrfs filesystem df /path
               Data, single: total=1.15TiB, used=1.13TiB
               System, single: total=32.00MiB, used=144.00KiB
               Metadata, single: total=12.00GiB, used=6.45GiB
               GlobalReserve, single: total=512.00MiB, used=0.00B

           ·   Data, System and Metadata are separeate block group types.  GlobalReserve is an
               artificial and internal emergency space, see below.

           ·   single — the allocation profile, defined at mkfs time

           ·   total — sum of space reserved for all allocation profiles of the given type, ie.
               all Data/single. Note that it’s not total size of filesystem.

           ·   used — sum of used space of the above, ie. file extents, metadata blocks

           GlobalReserve is an artificial and internal emergency space. It is used eg. when the
           filesystem is full. Its total size is dynamic based on the filesystem size, usually
           not larger than 512MiB, used may fluctuate.

           The global block reserve is accounted within Metadata. In case the filesystem metadata
           are exhausted, GlobalReserve/total + Metadata/used = Metadata/total.

           Options

           -b|--raw
               raw numbers in bytes, without the B suffix

           -h|--human-readable
               print human friendly numbers, base 1024, this is the default

           -H
               print human friendly numbers, base 1000

           --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

           -k|--kbytes
               show sizes in KiB, or kB with --si

           -m|--mbytes
               show sizes in MiB, or MB with --si

           -g|--gbytes
               show sizes in GiB, or GB with --si

           -t|--tbytes
               show sizes in TiB, or TB with --si

               If conflicting options are passed, the last one takes precedence.

       defragment [options] | [|...]
           Defragment file data on a mounted filesytem.

           If -r is passed, files in dir will be defragmented recursively. The start position and
           the number of bytes to defragment can be specified by start and len using -s and -l
           options below. Extents bigger than value given by -t will be skipped, otherwise this
           value is used as a target extent size, but is only advisory and may not be reached if
           the free space is too fragmented. Use 0 to take the kernel default, which is 256kB but
           may change in the future. You can also turn on compression in defragment operations.

               Warning
               Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as well as with Linux
               stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or ≥ 3.13.4 will break up the
               ref-links of COW data (for example files copied with cp --reflink, snapshots or
               de-duplicated data). This may cause considerable increase of space usage depending
               on the broken up ref-links.
           Options

           -v
               be verbose, print file names as they’re submitted for defragmentation

           -c[]
               compress file contents while defragmenting. Optional argument selects the
               compression algorithm, zlib (default) or lzo. Currently it’s not possible to
               select no compression. See also section EXAMPLES.

           -r
               defragment files recursively in given directories

           -f
               flush data for each file before going to the next file. This will limit the amount
               of dirty data to current file, otherwise the amount cumulates from several files
               and may increase system load.

           -s [kKmMgGtTpPeE]
               defragmentation will start from the given offset, default is beginning of a file

           -l [kKmMgGtTpPeE]
               defragment only up to len bytes, default is the file size

           -t [kKmMgGtTpPeE]
               target extent size, do not touch extents bigger than size

               For start, len, size it is possible to append units designator: 'K', 'M', 'G',
               'T', 'P', or 'E', which represent KiB, MiB, GiB, TiB, PiB, or EiB, respectively
               (case does not matter).

                   Note
                   Directory arguments without -r do not defragment files recursively but will
                   defragment certain internal trees (extent tree and the subvolume tree). This
                   has been confusing and could be removed in the future.

       label [|] []
           Show or update the label of a filesystem. This works on a mounted filesystem or a
           filesystem image.

           The newlabel argument is optional. Current label is printed if the the argument is
           omitted.

               Note
               the maximum allowable length shall be less than 256 chars and must not contain a
               newline. The trailing newline is stripped automatically.

       resize [:][+/-][kKmMgGtTpPeE]|[:]max 
           Resize a mounted filesystem identified by path. A particular device can be resized by
           specifying a devid.

               Warning
               If path is a file containing a BTRFS image then resize does not work as expected
               and does not resize the image. This would resize the underlying filesystem
               instead.
           The devid can be found in the output of btrfs filesystem show and defaults to 1 if not
           specified. The size parameter specifies the new size of the filesystem. If the prefix
           + or - is present the size is increased or decreased by the quantity size. If no units
           are specified, bytes are assumed for size. Optionally, the size parameter may be
           suffixed by one of the following units designators: 'K', 'M', 'G', 'T', 'P', or 'E',
           which represent KiB, MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter).

           If max is passed, the filesystem will occupy all available space on the device
           respecting devid (remember, devid 1 by default).

           The resize command does not manipulate the size of underlying partition. If you wish
           to enlarge/reduce a filesystem, you must make sure you can expand the partition before
           enlarging the filesystem and shrink the partition after reducing the size of the
           filesystem. This can done using fdisk(8) or parted(8) to delete the existing partition
           and recreate it with the new desired size. When recreating the partition make sure to
           use the same starting partition offset as before.

           Growing is usually instant as it only updates the size. However, shrinking could take
           a long time if there are data in the device area that’s beyond the new end. Relocation
           of the data takes time.

           See also section EXAMPLES.

       show [options] [|||

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