fstrim - discard unused blocks on a mounted filesystem


   fstrim [-a] [-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 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.


   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

   -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.


   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).


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


   mount(8), blkdiscard(8)


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


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