NAME

       fstrim - discard unused blocks on a mounted filesystem

SYNOPSIS

       fstrim [-Aa] [-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, --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.

       -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).

       --quiet
              Suppress error messages.  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.

       -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/.