Provided by: util-linux_2.27.1-6ubuntu2_i386 bug

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 the 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.   Default  value  is
              zero, discard 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

       mount(8)

AVAILABILITY

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