Provided by: util-linux_2.37.2-4ubuntu3.4_amd64 bug


       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

       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).

           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.




           all failed

           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 <>, Karel Zak <>


       blkdiscard(8), mount(8)


       For bug reports, use the issue tracker at


       The fstrim command is part of the util-linux package which can be downloaded from Linux
       Kernel Archive <>.