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/.