FSTRIM(8) System Administration FSTRIM(8)
NAME
fstrim - discard unused blocks on a mounted filesystem
SYNOPSIS
fstrim [-Aa] [-o offset] [-l length] [-m minimum-size] [-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.
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.
OPTIONS
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, autofs and
read-only filesystems are silently ignored. Filesystems with
"X-fstrim.notrim" mount option are skipped.
-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.
Filesystems with "X-fstrim.notrim" mount option in fstab are
skipped.
-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(8) 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 line.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
EXIT STATUS
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).
AUTHORS
Lukas Czerner <lczerner@redhat.com>, Karel Zak <kzak@redhat.com>
SEE ALSO
blkdiscard(8), mount(8)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
The fstrim command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>.
util-linux 2.38.1 2022-05-11 FSTRIM(8)
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