NAME

       fstrim - discard unused blocks on a mounted filesystem

SYNOPSIS

       fstrim [-a] [-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, --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 are silently ignored.

       -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.

       -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.   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).

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

       -h, --help
              Display help text and exit.

RETURN CODES

       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).

AUTHOR

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

SEE ALSO

       blkdiscard(8), mount(8)

AVAILABILITY

       The   fstrim   command   is   part   of    the    util-linux    package    and    is    available    from
       https://www.kernel.org/pub/linux/utils/util-linux/.

util-linux                                          July 2014                                          FSTRIM(8)