383 lines
14 KiB
Plaintext
383 lines
14 KiB
Plaintext
btrfs-filesystem(8)
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===================
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NAME
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----
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btrfs-filesystem - command group of btrfs that usually work on the whole filesystem
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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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*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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taks 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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+
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--
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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: 'mkfs.btrfs -d single -m single'
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--
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------------------------------
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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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------------------------------
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+
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--
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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 below.
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* 'single' -- the allocation profile, defined at mkfs time
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* 'total' -- sum of space reserved for
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all allocation profiles of the given type, ie. all Data/single. Note that it's
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not total size of filesystem.
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* 'used' -- sum of used space of the above, ie. file extents, metadata blocks
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--
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+
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'GlobalReserve' is an artificial and internal emergency space. It is used eg.
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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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+
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The global block reserve is accounted within Metadata. In case the filesystem
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metadata are exhausted, 'GlobalReserve/total + Metadata/used = Metadata/total'.
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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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*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.
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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 256kB but may change in the future.
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You can also turn on compression in defragment operations.
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+
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WARNING: 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 ref-links of COW data (for example files copied with `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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ref-links.
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+
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NOTE: 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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+
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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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-v::::
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be verbose, print file names as they're submitted for defragmentation
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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) or 'lzo'. 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
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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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cumulates 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 (ie. how the COW design works).
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+
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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: 32M
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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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*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 'btrfs fi 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. The 'set shared' value
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then is a sum of all shared space 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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*label* [<dev>|<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 the argument
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is omitted.
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NOTE: 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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// Some wording are extracted by the resize2fs man page
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*resize* [<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: 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 *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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units 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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can expand the partition before enlarging the filesystem and shrink the
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partition after reducing the size of the filesystem. This can done using
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`fdisk`(8) or `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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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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*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 /dev, otherwise the devices list is extracted from the
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/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'. This is done via a special ioctl and
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will also trigger cleaning of deleted subvolumes. Besides that it's equivalent
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to the `sync`(1) 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 *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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-------------------------
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$ btrfs fi 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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Used: 1.14TiB
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Free (estimated): 692.57GiB (min: 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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-------------------------
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The root user will also see stats broken down by block group types:
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-------------------------
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Data,single: Size:1.15TiB, Used:1.13TiB
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/dev/sdb 1.15TiB
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Metadata,single: Size:12.00GiB, Used:6.45GiB
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/dev/sdb 12.00GiB
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System,single: Size:32.00MiB, Used:144.00KiB
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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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-------------------------
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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 '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 '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 '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 '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
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even if run repeatedly.
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*$ btrfs filesystem resize -1G /path*
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*$ btrfs filesystem resize 1:-1G /path*
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Shrink size of the filesystem's device id 1 by 1GiB. The first syntax expects a
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device with id 1 to exist, otherwise fails. The second is equivalent and more
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explicit. For a single-device filesystem it's typically not necessary to
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specify the devid though.
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*$ btrfs filesystem resize max /path*
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*$ btrfs filesystem resize 1:max /path*
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Let's assume that devid 1 exists, the filesystem does not occupy the whole block
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device, eg. it has been enlarged and we wan the grow the filesystem. Simply using
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'max' as size we will achieve that.
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NOTE: There are two ways to minimize the filesystem on a given device. The
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*btrfs inspect-internal min-dev-size* command, or iteratively shrink in steps.
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EXIT STATUS
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-----------
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*btrfs filesystem* returns a zero exit status if it succeeds. Non zero is
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returned in case of failure.
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AVAILABILITY
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------------
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*btrfs* is part of btrfs-progs.
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Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
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further details.
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SEE ALSO
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--------
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`mkfs.btrfs`(8),
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