fstrim man page on ElementaryOS

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FSTRIM(8)		     System Administration		     FSTRIM(8)

       fstrim - discard unused blocks on a mounted filesystem

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

       The offset, length, and minimum-free-extent arguments may  be  followed
       by  binary  (2^N) suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is
       optional, e.g. "K" has the same meaning as  "KiB")  or  decimal	(10^N)
       suffixes KB, MB, GB, PB and EB.

       -h, --help
	      Print help 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).

       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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