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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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FSTRIM(8) System Administration FSTRIM(8)
fstrim - discard unused blocks on a mounted filesystem
fstrim [-v] [-o offset] [-l length] [-m minimum-size]
-A|-a|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 and is required when -A, -a, --fstab, or
--all are unspecified.
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, autofs and read-only filesystems
are silently ignored. Filesystems with "X-fstrim.notrim" mount
option are skipped.
-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.
Filesystems with "X-fstrim.notrim" mount option in fstab are
skipped.
-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.
-t, --types list
Specifies allowed or forbidden filesystem types when used with
--all or --fstab. The list is a comma-separated list of the
filesystem names. The list follows how mount -t evaluates type
patterns. Only specified filesystem types are allowed. All
specified types are forbidden if the list is prefixed by "no"
or each filesystem prefixed by "no" is forbidden. If the
option is not used, then all filesystems (except "autofs") are
allowed.
-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(8) 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. This option also
cleans exit status when unsupported filesystem specified on
fstrim command line.
-h, --help
Display help text and exit.
-V, --version
Display version 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 <[email protected]>, Karel Zak <[email protected]>
blkdiscard(8), mount(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The fstrim command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) 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 [email protected]
util-linux 2.42-start-521-ec46 2025-01-16 FSTRIM(8)
Pages that refer to this page: blkdiscard(8), dmeventd(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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