fstrim - discard unused blocks on a mounted filesystem
] [-o offset
] [-l length
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
argument is the pathname of the directory where the
filesystem is mounted.
frequently, or even using mount -o discard
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
, 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, --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 are
- -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.
- -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. 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
- -V, --version
- Display version information and exit.
- -h, --help
- Display help text and exit.
- all failed
- 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@example.com>
Karel Zak <firstname.lastname@example.org>
The fstrim command is part of the util-linux package and is available from