FSTRIM(8) System Administration FSTRIM(8)
NAME
fstrim - discard unused blocks on a mounted filesystem
SYNOPSIS
fstrim [-o offset] [-l length] [-m minimum-free-extent] [-v] mountpoint
DESCRIPTION
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.
OPTIONS
The offset, length, and minimum-free-extent 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.
-h, --help
Print help and exit.
-o, --offset offset
Byte offset in filesystem from which to begin searching for free blocks to discard. Default value is
zero, starting at the beginning of the filesystem.
-l, --length length
Number of bytes after 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. Default value
extends to the end of the filesystem.
-m, --minimum minimum-free-extent
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. Default value is zero, discard every free block.
-v, --verbose
Verbose execution. When specified 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 sec‐
tors 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).
AUTHOR
Lukas Czerner <[email protected]>
Karel Zak <[email protected]>
Back to main site | Back to man page index