fstrim man page on Mageia

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FSTRIM(8)		     System Administration		     FSTRIM(8)

NAME
       fstrim - discard unused blocks on a mounted filesystem

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

OPTIONS
       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.

       -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).

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/.

util-linux			 November 2010			     FSTRIM(8)
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