fstrim man page on Archlinux

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FSTRIM(8)		     System Administration		     FSTRIM(8)

       fstrim - discard unused blocks on a mounted filesystem

       fstrim  [-a]  [-o  offset]  [-l	length]	 [-m minimum-free-extent] [-v]

       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.

       The  offset,  length, and minimum-free-extent 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.

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

       -o, --offset offset
	      Byte offset in filesystem from which to begin searching for free
	      blocks to discard.  Default  value  is  zero,  starting  at  the
	      beginning of the filesystem.

       -l, --length length
	      Number  of  bytes after 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.
	      Default value extends to the end of the filesystem.

       -m, --minimum minimum-free-extent
	      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. When specified 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).

       0      success

       1      failure

       32     all failed

       64     some filesystem discards have succeeded, some failed

       The command fstrim --all returns 0 (all success), 32 (all failed) or 64
       (some failed, some success).

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


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

util-linux			 November 2010			     FSTRIM(8)

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