fstrim - discard unused blocks on a mounted filesystem
fstrim [-Aa] [-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, --fstab
- 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.
- -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,
read-only devices and read-only filesystems are silently ignored.
- -n, --dry-run
- This option does everything apart from actually call FITRIM ioctl.
- -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:
--listed-in /etc/fstab:/proc/self/mountinfo.
- -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.
- -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 option).
- --quiet-unsupported
- 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.
- -V, --version
- Display version information and exit.
- -h, --help
- Display help text and exit.
- 0
- success
- 1
- failure
- 32
- all failed
- 64
- 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 <lczerner@redhat.com>
Karel Zak <kzak@redhat.com>
The fstrim command is part of the util-linux package and is
available from https://www.kernel.org/pub/linux/utils/util-linux/.