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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | AUTHORS | SEE ALSO | AVAILABILITY | COLOPHON |
FSTRIM(8) System Administration FSTRIM(8)
fstrim - discard unused blocks on a mounted filesystem
fstrim [-Aa] [-o offset] [-l length] [-m minimum-size] [-v]
mountpoint
fstrim is used on a mounted filesystem to discard (or "trim") blocks
which are not in use by the filesystem. This is useful for solid-
state drives (SSDs) and thinly-provisioned storage.
By default, fstrim will discard all unused blocks in the filesystem.
Options may be used to modify this behavior based on range or size,
as explained below.
The mountpoint argument is the pathname of the directory where the
filesystem is mounted.
Running fstrim frequently, or even using mount -o discard, might
negatively affect the lifetime of poor-quality SSD devices. For most
desktop and server systems a sufficient trimming frequency is once a
week. Note that not all devices support a queued trim, so each trim
command incurs a performance penalty on whatever else might be trying
to use the disk at the time.
The offset, length, and minimum-size arguments may be followed by the
multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for
GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has
the same meaning as "KiB") or the suffixes KB (=1000), MB
(=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
-A, --fstab
Trim all mounted filesystems mentioned in /etc/fstab on
devices that support the discard operation. The root
filesystem is determined from kernel command line if missing
in the file. The other supplied options, like --offset,
--length and --minimum, are applied to all these devices.
Errors from filesystems that do not support the discard
operation, read-only devices and read-only filesystems are
silently ignored.
-a, --all
Trim all mounted filesystems on devices that support the
discard operation. The other supplied options, like --offset,
--length and --minimum, are applied to all these devices.
Errors from filesystems that do not support the discard
operation, read-only devices and read-only filesystems are
silently ignored.
-n, --dry-run
This option does everything apart from actually call FITRIM
ioctl.
-o, --offset offset
Byte offset in the filesystem from which to begin searching
for free blocks to discard. The default value is zero,
starting at the beginning of the filesystem.
-l, --length length
The number of bytes (after the starting point) to search for
free blocks to discard. If the specified value extends past
the end of the filesystem, fstrim will stop at the filesystem
size boundary. The default value extends to the end of the
filesystem.
-I, --listed-in list
Specifies a colon-separated list of files in fstab or kernel
mountinfo format. All missing or empty files are silently
ignored. The evaluation of the list stops after first non-
empty file. For example: --listed-in
/etc/fstab:/proc/self/mountinfo.
-m, --minimum minimum-size
Minimum contiguous free range to discard, in bytes. (This
value is internally rounded up to a multiple of the filesystem
block size.) Free ranges smaller than this will be ignored
and fstrim will adjust the minimum if it's smaller than the
device's minimum, and report that (fstrim_range.minlen) back
to userspace. By increasing this value, the fstrim operation
will complete more quickly for filesystems with badly
fragmented freespace, although not all blocks will be
discarded. The default value is zero, discarding every free
block.
-v, --verbose
Verbose execution. With this option fstrim will output the
number of bytes passed from the filesystem down the block
stack to the device for potential discard. This number is a
maximum discard amount from the storage device's perspective,
because FITRIM ioctl called repeated will keep sending the
same sectors for discard repeatedly.
fstrim will report the same potential discard bytes each time,
but only sectors which had been written to between the
discards would actually be discarded by the storage device.
Further, the kernel block layer reserves the right to adjust
the discard ranges to fit raid stripe geometry, non-trim
capable devices in a LVM setup, etc. These reductions would
not be reflected in fstrim_range.len (the --length option).
--quiet-unsupported
Suppress error messages if trim operation (ioctl) is
unsupported. This option is meant to be used in systemd
service file or in cron scripts to hide warnings that are
result of known problems, such as NTFS driver reporting Bad
file descriptor when device is mounted read-only, or lack of
file system support for ioctl FITRIM call.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
0 success
1 failure
32 all failed
64 some filesystem discards have succeeded, some failed
The command fstrim --all returns 0 (all succeeded), 32 (all failed)
or 64 (some failed, some succeeded).
Lukas Czerner <lczerner@redhat.com>
Karel Zak <kzak@redhat.com>
blkdiscard(8), mount(8)
The fstrim command is part of the util-linux package and is available
from https://www.kernel.org/pub/linux/utils/util-linux/.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-08-12.) 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
util-linux May 2019 FSTRIM(8)
Pages that refer to this page: blkdiscard(8)