BTRFS-FILESYSTEM(8)                     Btrfs Manual                     BTRFS-FILESYSTEM(8)

NAME
       btrfs-filesystem - command group that primarily does work on the whole filesystems

SYNOPSIS
       btrfs filesystem <subcommand> <args>

DESCRIPTION
       btrfs filesystem is used to perform several whole filesystem level tasks, including
       all the regular filesystem operations like resizing, space stats, label
       setting/getting, and defragmentation. There are other whole filesystem tasks like
       scrub or balance that are grouped in separate commands.

SUBCOMMAND
       df [options] <path>
           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 separate 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 GlobalReserve is a portion of Metadata. In case the filesystem metadata is
           exhausted, GlobalReserve/total + Metadata/used = Metadata/total. Otherwise there
           appears to be some unused space of Metadata.

           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] <file>|<dir> [<file>|<dir>...]
           Defragment file data on a mounted filesystem. Requires kernel 2.6.33 and newer.

           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
           length 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 reflinks 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 reflinks.

               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.
           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).

           Options

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

           -c[<algo>]
               compress file contents while defragmenting. Optional argument selects the
               compression algorithm, zlib (default), lzo or zstd. 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 accumulates from several files and will increase system load. This can
               also lead to ENOSPC if there’s too much dirty data to write and it’s not
               possible to make the reservations for the new data (ie. how the COW design
               works).

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

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

           -t <size>[kKmMgGtTpPeE]
               target extent size, do not touch extents bigger than size, default: 32M

               The value is only advisory and the final size of the extents may differ,
               depending on the state of the free space and fragmentation or other internal
               logic. Reasonable values are from tens to hundreds of megabytes.

       du [options] <path> [<path>..]
           Calculate disk usage of the target files using FIEMAP. For individual files, it
           will report a count of total bytes, and exclusive (not shared) bytes. We also
           calculate a set shared value which is described below.

           Each argument to btrfs filesystem du will have a set shared value calculated for
           it. We define each set as those files found by a recursive search of an argument.
           The set shared value then is a sum of all shared space referenced by the set.

           set shared takes into account overlapping shared extents, hence it isn’t as
           simple as adding up shared extents.

           Options

           -s|--summarize
               display only a total for each argument

           --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.

       label [<device>|<mountpoint>] [<newlabel>]
           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 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 [<devid>:][+/-]<size>[kKmMgGtTpPeE]|[<devid>:]max <path>
           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 unit 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] [<path>|<uuid>|<device>|<label>]
           Show the btrfs filesystem with some additional info about devices and space
           allocation.

           If no option none of path/uuid/device/label is passed, information about all the
           BTRFS filesystems is shown, both mounted and unmounted.

           Options

           -m|--mounted
               probe kernel for mounted BTRFS filesystems

           -d|--all-devices
               scan all devices under /dev, otherwise the devices list is extracted from the
               /proc/partitions file. This is a fallback option if there’s no device node
               manager (like udev) available in the system.

           --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

       sync <path>
           Force a sync of the filesystem at path. This is done via a special ioctl and will
           also trigger cleaning of deleted subvolumes. Besides that it’s equivalent to the
           sync(1) command.

       usage [options] <path> [<path>...]
           Show detailed information about internal filesystem usage. This is supposed to
           replace the btrfs filesystem df command in the long run.

           The level of detail can differ if the command is run under a regular or the root
           user (due to use of restricted ioctl). For both there’s a summary section with
           information about space usage:

               $ btrfs filesystem usage /path
               WARNING: cannot read detailed chunk info, RAID5/6 numbers will be incorrect, run as root
               Overall:
                   Device size:                   1.82TiB
                   Device allocated:              1.17TiB
                   Device unallocated:          669.99GiB
                   Device missing:                  0.00B
                   Used:                          1.14TiB
                   Free (estimated):            692.57GiB      (min: 692.57GiB)
                   Data ratio:                       1.00
                   Metadata ratio:                   1.00
                   Global reserve:              512.00MiB      (used: 0.00B)

           The root user will also see stats broken down by block group types:

               Data,single: Size:1.15TiB, Used:1.13TiB
                  /dev/sdb        1.15TiB

               Metadata,single: Size:12.00GiB, Used:6.45GiB
                  /dev/sdb       12.00GiB

               System,single: Size:32.00MiB, Used:144.00KiB
                  /dev/sdb       32.00MiB

               Unallocated:
                  /dev/sdb      669.99GiB

           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

           -T
               show data in tabular format

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

EXAMPLES
       $ btrfs filesystem defrag -v -r dir/

       Recursively defragment files under dir/, print files as they are processed. The file
       names will be printed in batches, similarly the amount of data triggered by
       defragmentation will be proportional to last N printed files. The system dirty memory
       throttling will slow down the defragmentation but there can still be a lot of IO load
       and the system may stall for a moment.

       $ btrfs filesystem defrag -v -r -f dir/

       Recursively defragment files under dir/, be verbose and wait until all blocks are
       flushed before processing next file. You can note slower progress of the output and
       lower IO load (proportional to currently defragmented file).

       $ btrfs filesystem defrag -v -r -f -clzo dir/

       Recursively defragment files under dir/, be verbose, wait until all blocks are
       flushed and force file compression.

       $ btrfs filesystem defrag -v -r -t 64M dir/

       Recursively defragment files under dir/, be verbose and try to merge extents to be
       about 64MiB. As stated above, the success rate depends on actual free space
       fragmentation and the final result is not guaranteed to meet the target even if run
       repeatedly.

       $ btrfs filesystem resize -1G /path

       $ btrfs filesystem resize 1:-1G /path

       Shrink size of the filesystem’s device id 1 by 1GiB. The first syntax expects a
       device with id 1 to exist, otherwise fails. The second is equivalent and more
       explicit. For a single-device filesystem it’s typically not necessary to specify the
       devid though.

       $ btrfs filesystem resize max /path

       $ btrfs filesystem resize 1:max /path

       Let’s assume that devid 1 exists and the filesystem does not occupy the whole block
       device, eg. it has been enlarged and we want to grow the filesystem. By simply using
       max as size we will achieve that.

           Note
           There are two ways to minimize the filesystem on a given device. The btrfs
           inspect-internal min-dev-size command, or iteratively shrink in steps.

EXIT STATUS
       btrfs filesystem 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 v4.20.1                            01/23/2019                      BTRFS-FILESYSTEM(8)

usage: btrfs filesystem [<group>] <command> [<args>]

    btrfs filesystem df [options] <path>
        Show space usage information for a mount point
    btrfs filesystem du [options] <path> [<path>..]
        Summarize disk usage of each file.
    btrfs filesystem show [options] [<path>|<uuid>|<device>|label]
        Show the structure of a filesystem
    btrfs filesystem sync <path>
        Force a sync on a filesystem
    btrfs filesystem defragment [options] <file>|<dir> [<file>|<dir>...]
        Defragment a file or a directory
    btrfs filesystem resize [devid:][+/-]<newsize>[kKmMgGtTpPeE]|[devid:]max <path>
        Resize a filesystem
    btrfs filesystem label [<device>|<mount_point>] [<newlabel>]
        Get or change the label of a filesystem
    btrfs filesystem usage [options] <path> [<path>..]
        Show detailed information about internal filesystem usage .

overall filesystem tasks and information