fstrim — discard unused blocks on a mounted filesystem
fstrim [−a] [ −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,
−−allTrim 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 silently
ignored.
−o,
−−offset offsetByte 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 lengthThe 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-sizeMinimum 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,
−−verboseVerbose 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).
−V,
−−versionDisplay version information and exit.
−h,
−−helpDisplay help text and exit.