fstrim

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 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.
           This option also cleans exit status when unsupported filesystem
           specified on fstrim command line.

       -V, --version
           Display version information and exit.

       -h, --help
           Display help text 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/karelzak/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 2.37.2                 2021-07-20                         FSTRIM(8)