Manual Reference Pages - FSTRIM (8)
fstrim - discard unused blocks on a mounted filesystem
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
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.
mountpoint argument is the pathname of the directory where the filesystem
The offset, length, and minimum-free-extent arguments may be
followed by binary (2^N) suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is
optional, e.g. "K" has the same meaning as "KiB") or decimal (10^N) suffixes
KB, MB, GB, PB and EB.
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
-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.
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 devices 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
Lukas Czerner <email@example.com>
Karel Zak <firstname.lastname@example.org>
The fstrim command is part of the util-linux-ng package and is available from
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.