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'\" t
.\"     Title: btrfs-filesystem
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 12/05/2018
.\"    Manual: Btrfs Manual
.\"    Source: Btrfs v4.19.1
.\"  Language: English
.\"
.TH "BTRFS\-FILESYSTEM" "8" "12/05/2018" "Btrfs v4\&.19\&.1" "Btrfs Manual"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
btrfs-filesystem \- command group that primarily does work on the whole filesystems
.SH "SYNOPSIS"
.sp
\fBbtrfs filesystem\fR \fI<subcommand>\fR \fI<args>\fR
.SH "DESCRIPTION"
.sp
\fBbtrfs filesystem\fR 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\&.
.SH "SUBCOMMAND"
.PP
\fBdf\fR [options] \fI<path>\fR
.RS 4
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\&.
.sp
An example with description:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
device size:
\fI1\&.9TiB\fR, one device, no RAID
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
filesystem size:
\fI1\&.9TiB\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
created with:
\fImkfs\&.btrfs \-d single \-m single\fR
.RE
.sp
.if n \{\
.RS 4
.\}
.nf
$ 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
.fi
.if n \{\
.RE
.\}
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIData\fR,
\fISystem\fR
and
\fIMetadata\fR
are separate block group types\&.
\fIGlobalReserve\fR
is an artificial and internal emergency space, see below\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIsingle\fR \(em the allocation profile, defined at mkfs time
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fItotal\fR \(em sum of space reserved for all allocation profiles of the given type, ie\&. all Data/single\&. Note that it\(cqs not total size of filesystem\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIused\fR \(em sum of used space of the above, ie\&. file extents, metadata blocks
.RE
.sp
\fIGlobalReserve\fR
is an artificial and internal emergency space\&. It is used eg\&. when the filesystem is full\&. Its
\fItotal\fR
size is dynamic based on the filesystem size, usually not larger than 512MiB,
\fIused\fR
may fluctuate\&.
.sp
The GlobalReserve is a portion of Metadata\&. In case the filesystem metadata is exhausted,
\fIGlobalReserve/total + Metadata/used = Metadata/total\fR\&. Otherwise there appears to be some unused space of Metadata\&.
.sp
\fBOptions\fR
.PP
\-b|\-\-raw
.RS 4
raw numbers in bytes, without the
\fIB\fR
suffix
.RE
.PP
\-h|\-\-human\-readable
.RS 4
print human friendly numbers, base 1024, this is the default
.RE
.PP
\-H
.RS 4
print human friendly numbers, base 1000
.RE
.PP
\-\-iec
.RS 4
select the 1024 base for the following options, according to the IEC standard
.RE
.PP
\-\-si
.RS 4
select the 1000 base for the following options, according to the SI standard
.RE
.PP
\-k|\-\-kbytes
.RS 4
show sizes in KiB, or kB with \-\-si
.RE
.PP
\-m|\-\-mbytes
.RS 4
show sizes in MiB, or MB with \-\-si
.RE
.PP
\-g|\-\-gbytes
.RS 4
show sizes in GiB, or GB with \-\-si
.RE
.PP
\-t|\-\-tbytes
.RS 4
show sizes in TiB, or TB with \-\-si
.sp
If conflicting options are passed, the last one takes precedence\&.
.RE
.RE
.PP
\fBdefragment\fR [options] \fI<file>\fR|\fI<dir>\fR [\fI<file>\fR|\fI<dir>\fR\&...]
.RS 4
Defragment file data on a mounted filesystem\&. Requires kernel 2\&.6\&.33 and newer\&.
.sp
If
\fI\-r\fR
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
\fI\-s\fR
and
\fI\-l\fR
options below\&. Extents bigger than value given by
\fI\-t\fR
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\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBWarning\fR
.ps -1
.br
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
\fBcp \-\-reflink\fR, snapshots or de\-duplicated data)\&. This may cause considerable increase of space usage depending on the broken up reflinks\&.
.sp .5v
.RE
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
Directory arguments without
\fI\-r\fR
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\&.
.sp .5v
.RE
For
\fIstart\fR,
\fIlen\fR,
\fIsize\fR
it is possible to append units designator: \*(AqK\*(Aq, \*(AqM\*(Aq, \*(AqG\*(Aq, \*(AqT\*(Aq, \*(AqP\*(Aq, or \*(AqE\*(Aq, which represent KiB, MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter)\&.
.sp
\fBOptions\fR
.PP
\-v
.RS 4
be verbose, print file names as they\(cqre submitted for defragmentation
.RE
.PP
\-c[\fI<algo>\fR]
.RS 4
compress file contents while defragmenting\&. Optional argument selects the compression algorithm,
\fIzlib\fR
(default),
\fIlzo\fR
or
\fIzstd\fR\&. Currently it\(cqs not possible to select no compression\&. See also section
\fIEXAMPLES\fR\&.
.RE
.PP
\-r
.RS 4
defragment files recursively in given directories
.RE
.PP
\-f
.RS 4
flush data for each file before going to the next file\&.
.sp
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\(cqs too much dirty data to write and it\(cqs not possible to make the reservations for the new data (ie\&. how the COW design works)\&.
.RE
.PP
\-s \fI<start>\fR[kKmMgGtTpPeE]
.RS 4
defragmentation will start from the given offset, default is beginning of a file
.RE
.PP
\-l \fI<len>\fR[kKmMgGtTpPeE]
.RS 4
defragment only up to
\fIlen\fR
bytes, default is the file size
.RE
.PP
\-t \fI<size>\fR[kKmMgGtTpPeE]
.RS 4
target extent size, do not touch extents bigger than
\fIsize\fR, default: 32M
.sp
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\&.
.RE
.RE
.PP
\fBdu\fR [options] \fI<path>\fR [\fI<path>\fR\&.\&.]
.RS 4
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
\fIset shared\fR
value which is described below\&.
.sp
Each argument to
\fIbtrfs filesystem du\fR
will have a
\fIset shared\fR
value calculated for it\&. We define each
\fIset\fR
as those files found by a recursive search of an argument\&. The
\fIset shared\fR
value then is a sum of all shared space referenced by the set\&.
.sp
\fIset shared\fR
takes into account overlapping shared extents, hence it isn\(cqt as simple as adding up shared extents\&.
.sp
\fBOptions\fR
.PP
\-s|\-\-summarize
.RS 4
display only a total for each argument
.RE
.PP
\-\-raw
.RS 4
raw numbers in bytes, without the
\fIB\fR
suffix\&.
.RE
.PP
\-\-human\-readable
.RS 4
print human friendly numbers, base 1024, this is the default
.RE
.PP
\-\-iec
.RS 4
select the 1024 base for the following options, according to the IEC standard\&.
.RE
.PP
\-\-si
.RS 4
select the 1000 base for the following options, according to the SI standard\&.
.RE
.PP
\-\-kbytes
.RS 4
show sizes in KiB, or kB with \-\-si\&.
.RE
.PP
\-\-mbytes
.RS 4
show sizes in MiB, or MB with \-\-si\&.
.RE
.PP
\-\-gbytes
.RS 4
show sizes in GiB, or GB with \-\-si\&.
.RE
.PP
\-\-tbytes
.RS 4
show sizes in TiB, or TB with \-\-si\&.
.RE
.RE
.PP
\fBlabel\fR [\fI<device>\fR|\fI<mountpoint>\fR] [\fI<newlabel>\fR]
.RS 4
Show or update the label of a filesystem\&. This works on a mounted filesystem or a filesystem image\&.
.sp
The
\fInewlabel\fR
argument is optional\&. Current label is printed if the argument is omitted\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
the maximum allowable length shall be less than 256 chars and must not contain a newline\&. The trailing newline is stripped automatically\&.
.sp .5v
.RE
.RE
.PP
\fBresize\fR [\fI<devid>\fR:][+/\-]\fI<size>\fR[kKmMgGtTpPeE]|[\fI<devid>\fR:]max \fI<path>\fR
.RS 4
Resize a mounted filesystem identified by
\fIpath\fR\&. A particular device can be resized by specifying a
\fIdevid\fR\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBWarning\fR
.ps -1
.br
If
\fIpath\fR
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\&.
.sp .5v
.RE
The
\fIdevid\fR
can be found in the output of
\fBbtrfs filesystem show\fR
and defaults to 1 if not specified\&. The
\fIsize\fR
parameter specifies the new size of the filesystem\&. If the prefix
\fI+\fR
or
\fI\-\fR
is present the size is increased or decreased by the quantity
\fIsize\fR\&. If no units are specified, bytes are assumed for
\fIsize\fR\&. Optionally, the size parameter may be suffixed by one of the following unit designators: \*(AqK\*(Aq, \*(AqM\*(Aq, \*(AqG\*(Aq, \*(AqT\*(Aq, \*(AqP\*(Aq, or \*(AqE\*(Aq, which represent KiB, MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter)\&.
.sp
If
\fImax\fR
is passed, the filesystem will occupy all available space on the device respecting
\fIdevid\fR
(remember, devid 1 by default)\&.
.sp
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
\fBfdisk\fR(8) or
\fBparted\fR(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\&.
.sp
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\(cqs beyond the new end\&. Relocation of the data takes time\&.
.sp
See also section
\fIEXAMPLES\fR\&.
.RE
.PP
\fBshow\fR [options] [\fI<path>\fR|\fI<uuid>\fR|\fI<device>\fR|\fI<label>\fR]
.RS 4
Show the btrfs filesystem with some additional info about devices and space allocation\&.
.sp
If no option none of
\fIpath\fR/\fIuuid\fR/\fIdevice\fR/\fIlabel\fR
is passed, information about all the BTRFS filesystems is shown, both mounted and unmounted\&.
.sp
\fBOptions\fR
.PP
\-m|\-\-mounted
.RS 4
probe kernel for mounted BTRFS filesystems
.RE
.PP
\-d|\-\-all\-devices
.RS 4
scan all devices under /dev, otherwise the devices list is extracted from the /proc/partitions file\&. This is a fallback option if there\(cqs no device node manager (like udev) available in the system\&.
.RE
.PP
\-\-raw
.RS 4
raw numbers in bytes, without the
\fIB\fR
suffix
.RE
.PP
\-\-human\-readable
.RS 4
print human friendly numbers, base 1024, this is the default
.RE
.PP
\-\-iec
.RS 4
select the 1024 base for the following options, according to the IEC standard
.RE
.PP
\-\-si
.RS 4
select the 1000 base for the following options, according to the SI standard
.RE
.PP
\-\-kbytes
.RS 4
show sizes in KiB, or kB with \-\-si
.RE
.PP
\-\-mbytes
.RS 4
show sizes in MiB, or MB with \-\-si
.RE
.PP
\-\-gbytes
.RS 4
show sizes in GiB, or GB with \-\-si
.RE
.PP
\-\-tbytes
.RS 4
show sizes in TiB, or TB with \-\-si
.RE
.RE
.PP
\fBsync\fR \fI<path>\fR
.RS 4
Force a sync of the filesystem at
\fIpath\fR\&. This is done via a special ioctl and will also trigger cleaning of deleted subvolumes\&. Besides that it\(cqs equivalent to the
\fBsync\fR(1) command\&.
.RE
.PP
\fBusage\fR [options] \fI<path>\fR [\fI<path>\fR\&...]
.RS 4
Show detailed information about internal filesystem usage\&. This is supposed to replace the
\fBbtrfs filesystem df\fR
command in the long run\&.
.sp
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\(cqs a summary section with information about space usage:
.sp
.if n \{\
.RS 4
.\}
.nf
$ 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)
.fi
.if n \{\
.RE
.\}
.sp
The root user will also see stats broken down by block group types:
.sp
.if n \{\
.RS 4
.\}
.nf
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
.fi
.if n \{\
.RE
.\}
.sp
\fBOptions\fR
.PP
\-b|\-\-raw
.RS 4
raw numbers in bytes, without the
\fIB\fR
suffix
.RE
.PP
\-h|\-\-human\-readable
.RS 4
print human friendly numbers, base 1024, this is the default
.RE
.PP
\-H
.RS 4
print human friendly numbers, base 1000
.RE
.PP
\-\-iec
.RS 4
select the 1024 base for the following options, according to the IEC standard
.RE
.PP
\-\-si
.RS 4
select the 1000 base for the following options, according to the SI standard
.RE
.PP
\-k|\-\-kbytes
.RS 4
show sizes in KiB, or kB with \-\-si
.RE
.PP
\-m|\-\-mbytes
.RS 4
show sizes in MiB, or MB with \-\-si
.RE
.PP
\-g|\-\-gbytes
.RS 4
show sizes in GiB, or GB with \-\-si
.RE
.PP
\-t|\-\-tbytes
.RS 4
show sizes in TiB, or TB with \-\-si
.RE
.PP
\-T
.RS 4
show data in tabular format
.sp
If conflicting options are passed, the last one takes precedence\&.
.RE
.RE
.SH "EXAMPLES"
.sp
\fB$ btrfs filesystem defrag \-v \-r dir/\fR
.sp
Recursively defragment files under \fIdir/\fR, 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\&.
.sp
\fB$ btrfs filesystem defrag \-v \-r \-f dir/\fR
.sp
Recursively defragment files under \fIdir/\fR, 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)\&.
.sp
\fB$ btrfs filesystem defrag \-v \-r \-f \-clzo dir/\fR
.sp
Recursively defragment files under \fIdir/\fR, be verbose, wait until all blocks are flushed and force file compression\&.
.sp
\fB$ btrfs filesystem defrag \-v \-r \-t 64M dir/\fR
.sp
Recursively defragment files under \fIdir/\fR, 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\&.
.sp
\fB$ btrfs filesystem resize \-1G /path\fR
.sp
\fB$ btrfs filesystem resize 1:\-1G /path\fR
.sp
Shrink size of the filesystem\(cqs 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\(cqs typically not necessary to specify the devid though\&.
.sp
\fB$ btrfs filesystem resize max /path\fR
.sp
\fB$ btrfs filesystem resize 1:max /path\fR
.sp
Let\(cqs 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 \fImax\fR as size we will achieve that\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
.sp
There are two ways to minimize the filesystem on a given device\&. The \fBbtrfs inspect\-internal min\-dev\-size\fR command, or iteratively shrink in steps\&.
.sp .5v
.RE
.SH "EXIT STATUS"
.sp
\fBbtrfs filesystem\fR returns a zero exit status if it succeeds\&. Non zero is returned in case of failure\&.
.SH "AVAILABILITY"
.sp
\fBbtrfs\fR is part of btrfs\-progs\&. Please refer to the btrfs wiki \m[blue]\fBhttp://btrfs\&.wiki\&.kernel\&.org\fR\m[] for further details\&.
.SH "SEE ALSO"
.sp
\fBmkfs\&.btrfs\fR(8),