fstrim - discard unused blocks on a mounted filesystem

       Lukas Czerner <lczerner@redhat.com>, Karel Zak <kzak@redhat.com>

       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 2.41                                    2025-02-26                                          FSTRIM(8)

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 and is required
       when -A,-a,--fstab,or--allareunspecified.Runningfstrimfrequently,orevenusingmount-odiscard,mightnegativelyaffectthelifetimeofpoor-qualitySSDdevices.Formostdesktopandserversystemsasufficienttrimmingfrequencyisonceaweek.Notethatnotalldevicessupportaqueuedtrim,soeachtrimcommandincursaperformancepenaltyonwhateverelsemightbetryingtousethediskatthetime.

       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).

       fstrim - discard unused blocks on a mounted filesystem

       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,--offsetoffset
           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,--lengthlength
           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-inlist
           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,--minimumminimum-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.

       -t, --typeslist
           Specifies allowed or forbidden filesystem types when used with --all or --fstab. The list is a
           comma-separated list of the filesystem names. The list follows how mount-t evaluates type patterns.
           Only specified filesystem types are allowed. All specified types are forbidden if the list is
           prefixed by "no" or each filesystem prefixed by "no" is forbidden. If the option is not used, then
           all filesystems (except "autofs") are allowed.

       -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 Badfiledescriptor 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
           Display version and exit.

       For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>.

blkdiscard(8), mount(8)

fstrim [-v] [-ooffset] [-llength] [-mminimum-size] -A|-a|mountpoint