NAME | SYNOPSIS | DESCRIPTION | SUBCOMMAND | EXAMPLES | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON

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

NAME         top

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

SYNOPSIS         top

       btrfs filesystem <subcommand> <args>

DESCRIPTION         top

       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         top

       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 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] <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 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.

               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 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         top

       $ 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, the filesystem does not occupy the
       whole block device, eg. it has been enlarged and we wan the grow the
       filesystem. 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         top

       btrfs filesystem returns a zero exit status if it succeeds. Non zero
       is returned in case of failure.

AVAILABILITY         top

       btrfs is part of btrfs-progs. Please refer to the btrfs wiki
       http://btrfs.wiki.kernel.org for further details.

SEE ALSO         top

       mkfs.btrfs(8),

COLOPHON         top

       This page is part of the btrfs-progs (btrfs filesystem tools)
       project.  Information about the project can be found at 
       ⟨https://btrfs.wiki.kernel.org/index.php/Btrfs_source_repositories⟩.
       If you have a bug report for this manual page, see
       ⟨https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#How_do_I_report_bugs_and_issues.3F⟩.
       This page was obtained from the project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git⟩
       on 2017-11-25.  (At that time, the date of the most recent commit
       that was found in the repository was 2017-11-20.)  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

Btrfs v4.6.1                     11/23/2017              BTRFS-FILESYSTEM(8)

Pages that refer to this page: btrfs(8)