5a956bb3b1
A user who wants to shrink a btrfs filesystem within some other logical device (like a partition) will likely want to adapt the size of the underlying device, too. This commit adds documentation that describes how the length of the portion that btrfs uses of some device can be found out. Thanks go out to Roman Mamedov <rm@romanrm.net> for hinting `btrfs filesystem show` as alternative command. Note: the granularity is one sectorsize and the input values are silently rounded down to avoid bugs from converted filesystems that would not adhere to the native btrfs constraints. [ci skip] Pull-request: #775 Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name> Signed-off-by: David Sterba <dsterba@suse.com>
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22 KiB
ReStructuredText
504 lines
22 KiB
ReStructuredText
btrfs-filesystem(8)
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===================
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SYNOPSIS
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--------
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**btrfs filesystem** <subcommand> <args>
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DESCRIPTION
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-----------
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:command:`btrfs filesystem` is used to perform several whole filesystem level tasks,
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including all the regular filesystem operations like resizing, space stats,
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label setting/getting, and defragmentation. There are other whole filesystem
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tasks like scrub or balance that are grouped in separate commands.
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SUBCOMMAND
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----------
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df [options] <path>
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Show a terse summary information about allocation of block group types of a given
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mount point. The original purpose of this command was a debugging helper. The
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output needs to be further interpreted and is not suitable for quick overview.
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An example with description:
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* device size: *1.9TiB*, one device, no RAID
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* filesystem size: *1.9TiB*
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* created with: :command:`mkfs.btrfs -d single -m single`
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.. code-block:: none
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$ btrfs filesystem df /path
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Data, single: total=1.15TiB, used=1.13TiB
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System, single: total=32.00MiB, used=144.00KiB
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Metadata, single: total=12.00GiB, used=6.45GiB
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GlobalReserve, single: total=512.00MiB, used=0.00B
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* *Data*, *System* and *Metadata* are separate block group types.
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*GlobalReserve* is an artificial and internal emergency space, see
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below.
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* *single* -- the allocation profile, defined at mkfs time
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* *total* -- sum of space reserved for all allocation profiles of the
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given type, i.e. all Data/single. Note that it's not total size of
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filesystem.
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* *used* -- sum of used space of the above, i.e. file extents, metadata blocks
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*GlobalReserve* is an artificial and internal emergency space. It is used e.g.
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when the filesystem is full. Its *total* size is dynamic based on the
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filesystem size, usually not larger than 512MiB, *used* may fluctuate.
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The GlobalReserve is a portion of Metadata. In case the filesystem metadata is
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exhausted, *GlobalReserve/total + Metadata/used = Metadata/total*. Otherwise
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there appears to be some unused space of Metadata.
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``Options``
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-b|--raw
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raw numbers in bytes, without the *B* suffix
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-h|--human-readable
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print human friendly numbers, base 1024, this is the default
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-H
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print human friendly numbers, base 1000
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--iec
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select the 1024 base for the following options, according to the IEC standard
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--si
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select the 1000 base for the following options, according to the SI standard
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-k|--kbytes
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show sizes in KiB, or kB with --si
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-m|--mbytes
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show sizes in MiB, or MB with --si
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-g|--gbytes
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show sizes in GiB, or GB with --si
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-t|--tbytes
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show sizes in TiB, or TB with --si
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If conflicting options are passed, the last one takes precedence.
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.. _man-filesystem-cmd-defragment:
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defragment [options] <file>|<dir> [<file>|<dir>...]
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Defragment file data on a mounted filesystem. Requires kernel 2.6.33 and newer.
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If *-r* is passed, files in dir will be defragmented recursively (not
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descending to subvolumes, mount points and directory symlinks).
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The start position and the number of bytes to defragment can be specified by
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start and length using *-s* and *-l* options below.
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Extents bigger than value given by *-t* will be skipped, otherwise this value
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is used as a target extent size, but is only advisory and may not be reached
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if the free space is too fragmented.
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Use 0 to take the kernel default, which is 256KiB but may change in the future.
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You can also turn on compression in defragment operations.
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.. warning::
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Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as well as
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with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or ≥ 3.13.4 will break up
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the reflinks of COW data (for example files copied with :command:`cp --reflink`,
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snapshots or de-duplicated data).
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This may cause considerable increase of space usage depending on the broken up
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reflinks.
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.. note::
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Directory arguments without *-r* do not defragment files recursively but will
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defragment certain internal trees (extent tree and the subvolume tree). This has been
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confusing and could be removed in the future.
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For *start*, *len*, *size* it is possible to append
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units designator: *K*, *M*, *G*, *T*, *P*, or *E*, which represent
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KiB, MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter).
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``Options``
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-c[<algo>]
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compress file contents while defragmenting. Optional argument selects the compression
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algorithm, *zlib* (default), *lzo* or *zstd*. Currently it's not possible to select no
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compression. See also section *EXAMPLES*.
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-r
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defragment files recursively in given directories, does not descend to
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subvolumes or mount points
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-f
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flush data for each file before going to the next file.
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This will limit the amount of dirty data to current file, otherwise the amount
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accumulates from several files and will increase system load. This can also lead
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to ENOSPC if there's too much dirty data to write and it's not possible to make
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the reservations for the new data (i.e. how the COW design works).
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-s <start>[kKmMgGtTpPeE]
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defragmentation will start from the given offset, default is beginning of a file
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-l <len>[kKmMgGtTpPeE]
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defragment only up to *len* bytes, default is the file size
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-t <size>[kKmMgGtTpPeE]
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target extent size, do not touch extents bigger than *size*, default: 32MiB
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The value is only advisory and the final size of the extents may differ,
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depending on the state of the free space and fragmentation or other internal
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logic. Reasonable values are from tens to hundreds of megabytes.
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--step SIZE
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Perform defragmention in the range in SIZE steps and flush (*-f*) after each one.
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The range is default (the whole file) or given by *-s* and *-l*, split into
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the steps or done in one go if the step is larger. Minimum range size is 256KiB.
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-v
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(deprecated) alias for global *-v* option
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du [options] <path> [<path>..]
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Calculate disk usage of the target files using FIEMAP. For individual
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files, it will report a count of total bytes, and exclusive (not
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shared) bytes. We also calculate a 'set shared' value which is
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described below.
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Each argument to :command:`btrfs filesystem du` will have a *set shared* value
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calculated for it. We define each *set* as those files found by a
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recursive search of an argument (recursion descends to subvolumes but not
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mount points). The *set shared* value then is a sum of all shared space
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referenced by the set.
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*set shared* takes into account overlapping shared extents, hence it
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isn't as simple as adding up shared extents.
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``Options``
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-s|--summarize
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display only a total for each argument
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--raw
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raw numbers in bytes, without the *B* suffix.
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--human-readable
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print human friendly numbers, base 1024, this is the default
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--iec
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select the 1024 base for the following options, according to the IEC standard.
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--si
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select the 1000 base for the following options, according to the SI standard.
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--kbytes
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show sizes in KiB, or kB with --si.
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--mbytes
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show sizes in MiB, or MB with --si.
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--gbytes
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show sizes in GiB, or GB with --si.
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--tbytes
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show sizes in TiB, or TB with --si.
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.. _man-filesystem-label:
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label [<device>|<mountpoint>] [<newlabel>]
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Show or update the label of a filesystem. This works on a mounted filesystem or
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a filesystem image.
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The *newlabel* argument is optional. Current label is printed if the argument
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is omitted.
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.. note::
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The maximum allowable length shall be less than 256 chars and must not contain
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a newline. The trailing newline is stripped automatically.
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mkswapfile [-s size] file
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Create a new file that's suitable and formatted as a swapfile. Default
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size is 2GiB, fixed page size 4KiB, minimum size is 40KiB.
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A swapfile must be created in a specific way: NOCOW and preallocated.
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Subvolume containing a swapfile cannot be snapshotted and blocks of an
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activated swapfile cannot be balanced.
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Swapfile creation can be achieved by standalone commands too. Activation
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needs to be done by command :manref:`swapon(8)`. See also command
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:command:`btrfs inspect-internal map-swapfile`
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and the :doc:`Swapfile feature<Swapfile>` description.
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.. note::
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The command is a simplified version of 'mkswap', if you want to set
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label, page size, or other parameters please use 'mkswap' proper.
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``Options``
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-s|--size SIZE
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Create swapfile of a given size SIZE (accepting k/m/g/e/p
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suffix).
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-U|--uuid UUID
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specify UUID to use, or a special value: clear (all zeros), random,
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time (time-based random)
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.. _man-filesystem-resize:
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resize [options] [<devid>:][+/-]<size>[kKmMgGtTpPeE]|[<devid>:]max <path>
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Resize a mounted filesystem identified by *path*. A particular device
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can be resized by specifying a *devid*.
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.. warning::
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If *path* is a file containing a BTRFS image then resize does not work
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as expected and does not resize the image. This would resize the underlying
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filesystem instead.
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The *devid* can be found in the output of :command:`btrfs filesystem show` and
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defaults to 1 if not specified.
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The *size* parameter specifies the new size of the filesystem.
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If the prefix *+* or *-* is present the size is increased or decreased
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by the quantity *size*.
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If no units are specified, bytes are assumed for *size*.
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Optionally, the size parameter may be suffixed by one of the following
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unit designators: *K*, *M*, *G*, *T*, *P*, or *E*, which represent
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KiB, MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter).
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If *max* is passed, the filesystem will occupy all available space on the
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device respecting *devid* (remember, devid 1 by default).
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The resize command does not manipulate the size of underlying
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partition. If you wish to enlarge/reduce a filesystem, you must make sure you
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expand the partition before enlarging the filesystem and shrink the
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partition after reducing the size of the filesystem. This can be done using
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:manref:`fdisk(8)` or :manref:`parted(8)` to delete the existing partition and recreate
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it with the new desired size. When recreating the partition make sure to use
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the same starting partition offset as before.
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The size of the portion that the filesystem uses of an underlying device can be
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determined via the :command:`btrfs filesystem show --raw` command on the
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filesystem’s mount point (where it’s given for each *devid* after the string
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`size` or via the :command:`btrfs inspect-internal dump-super` command on the
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specific device (where it’s given as the value of `dev_item.total_bytes`, which
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is not to be confused with `total_bytes`).
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The value is also the address of the first byte not used by the
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filesystem.
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Growing is usually instant as it only updates the size. However, shrinking could
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take a long time if there are data in the device area that's beyond the new
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end. Relocation of the data takes time.
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See also section *EXAMPLES*.
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``Options``
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--enqueue
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wait if there's another exclusive operation running, otherwise continue
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show [options] [<path>|<uuid>|<device>|<label>]
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Show the btrfs filesystem with some additional info about devices and space
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allocation.
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If no option none of *path*/*uuid*/*device*/*label* is passed, information
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about all the BTRFS filesystems is shown, both mounted and unmounted.
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``Options``
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-m|--mounted
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probe kernel for mounted BTRFS filesystems
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-d|--all-devices
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scan all devices under :file:`/dev`, otherwise the devices list is extracted from the
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:file:`/proc/partitions` file. This is a fallback option if there's no device node
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manager (like udev) available in the system.
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--raw
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raw numbers in bytes, without the *B* suffix
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--human-readable
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print human friendly numbers, base 1024, this is the default
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--iec
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select the 1024 base for the following options, according to the IEC standard
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--si
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select the 1000 base for the following options, according to the SI standard
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--kbytes
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show sizes in KiB, or kB with --si
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--mbytes
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show sizes in MiB, or MB with --si
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--gbytes
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show sizes in GiB, or GB with --si
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--tbytes
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show sizes in TiB, or TB with --si
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sync <path>
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Force a sync of the filesystem at *path*, similar to the :manref:`sync(1)` command. In
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addition, it starts cleaning of deleted subvolumes. To wait for the subvolume
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deletion to complete use the :command:`btrfs subvolume sync` command.
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usage [options] <path> [<path>...]
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Show detailed information about internal filesystem usage. This is supposed to
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replace the :command:`btrfs filesystem df` command in the long run.
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The level of detail can differ if the command is run under a regular or the
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root user (due to use of restricted ioctl). For both there's a summary section
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with information about space usage:
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.. code-block:: none
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$ btrfs filesystem usage /path
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WARNING: cannot read detailed chunk info, RAID5/6 numbers will be incorrect, run as root
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Overall:
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Device size: 1.82TiB
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Device allocated: 1.17TiB
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Device unallocated: 669.99GiB
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Device missing: 0.00B
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Device slack: 1.00GiB
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Used: 1.14TiB
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Free (estimated): 692.57GiB (min: 692.57GiB)
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Free (statfs, df) 692.57GiB
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Data ratio: 1.00
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Metadata ratio: 1.00
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Global reserve: 512.00MiB (used: 0.00B)
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Multiple profiles: no
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* *Device size* -- sum of raw device capacity available to the
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filesystem, note that this may not be the same as the total device
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size (the difference is accounted as slack)
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* *Device allocated* -- sum of total space allocated for
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data/metadata/system profiles, this also accounts space reserved but
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not yet used for extents
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* *Device unallocated* -- the remaining unallocated space for future
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allocations (difference of the above two numbers)
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* *Device missing* -- sum of capacity of all missing devices
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* *Device slack* -- sum of slack space on all devices (difference
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between entire device size and the space occupied by filesystem)
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* *Used* -- sum of the used space of data/metadata/system profiles, not
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including the reserved space
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* *Free (estimated)* -- approximate size of the remaining free space
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usable for data, including currently allocated space and estimating
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the usage of the unallocated space based on the block group profiles,
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the *min* is the lower bound of the estimate in case multiple
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profiles are present
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* *Free (statfs, df)* -- the amount of space available for data as
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reported by the **statfs/statvfs** syscall, also returned as *Avail* in the
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output of **df**. The value is calculated in a different way and may
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not match the estimate in some cases (e.g. multiple profiles).
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* *Data ratio* -- ratio of total space for data including redundancy or
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parity to the effectively usable data space, e.g. single is 1.0, RAID1
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is 2.0 and for RAID5/6 it depends on the number of devices
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* *Metadata ratio* -- ditto, for metadata
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* *Global reserve* -- portion of metadata currently used for global
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block reserve, used for emergency purposes (like deletion on a full
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filesystem)
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* *Multiple profiles* -- what block group types (data, metadata) have
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more than one profile (single, raid1, ...), see :doc:`btrfs-man5` section
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:ref:`FILESYSTEMS WITH MULTIPLE PROFILES<man-btrfs5-filesystem-with-multiple-profiles>`.
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And on a zoned filesystem there are two more lines in the *Device* section:
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.. code-block:: none
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Device zone unusable: 5.13GiB
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Device zone size: 256.00MiB
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* *Device zone unusable* -- sum of of space that's been used in the
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past but now is not due to COW and not referenced anymore, the chunks
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have to be reclaimed and zones reset to make it usable again
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* *Device zone size* -- the reported zone size of the host-managed
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device, same for all devices
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The root user will also see stats broken down by block group types:
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.. code-block:: none
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Data,single: Size:1.15TiB, Used:1.13TiB (98.26%)
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/dev/sdb 1.15TiB
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Metadata,single: Size:12.00GiB, Used:6.45GiB (53.75%)
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/dev/sdb 12.00GiB
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System,single: Size:32.00MiB, Used:144.00KiB (0.44%)
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/dev/sdb 32.00MiB
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Unallocated:
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/dev/sdb 669.99GiB
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*Data* is block group type, *single* is block group profile, *Size* is total
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size occupied by this type, *Used* is the actually used space, the percent is
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ratio of *Used/Size*. The *Unallocated* is remaining space.
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``Options``
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-b|--raw
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raw numbers in bytes, without the *B* suffix
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-h|--human-readable
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print human friendly numbers, base 1024, this is the default
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-H
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print human friendly numbers, base 1000
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--iec
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select the 1024 base for the following options, according to the IEC standard
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--si
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select the 1000 base for the following options, according to the SI standard
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-k|--kbytes
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show sizes in KiB, or kB with --si
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-m|--mbytes
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show sizes in MiB, or MB with --si
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-g|--gbytes
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show sizes in GiB, or GB with --si
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-t|--tbytes
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show sizes in TiB, or TB with --si
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-T
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show data in tabular format
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If conflicting options are passed, the last one takes precedence.
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EXAMPLES
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--------
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**$ btrfs filesystem defrag -v -r dir/**
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Recursively defragment files under :file:`dir/`, print files as they are processed.
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The file names will be printed in batches, similarly the amount of data triggered
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by defragmentation will be proportional to last N printed files. The system dirty
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memory throttling will slow down the defragmentation but there can still be a lot
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of IO load and the system may stall for a moment.
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**$ btrfs filesystem defrag -v -r -f dir/**
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Recursively defragment files under :file:`dir/`, be verbose and wait until all blocks
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are flushed before processing next file. You can note slower progress of the
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output and lower IO load (proportional to currently defragmented file).
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**$ btrfs filesystem defrag -v -r -f -clzo dir/**
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Recursively defragment files under :file:`dir/`, be verbose, wait until all blocks are
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flushed and force file compression.
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**$ btrfs filesystem defrag -v -r -t 64M dir/**
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Recursively defragment files under :file:`dir/`, be verbose and try to merge extents
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to be about 64MiB. As stated above, the success rate depends on actual free
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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, e.g. 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
|
||
:command:`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 documentation at
|
||
`https://btrfs.readthedocs.io <https://btrfs.readthedocs.io>`_.
|
||
|
||
SEE ALSO
|
||
--------
|
||
|
||
:doc:`btrfs-subvolume`,
|
||
:doc:`mkfs.btrfs`
|