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.
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 and read-only
filesystems are silently ignored.
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.
This option does everything apart from actually call
-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:
-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.
Verbose execution. With this option fstrim
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
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).
Suppress error messages if trim operation (ioctl) is
unsupported. This option is meant to be used in systemd service file or in
cron 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
Display version information and exit.
Display help text and exit.