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BLKDISCARD(8)		     System Administration		 BLKDISCARD(8)

NAME
       blkdiscard - discard sectors on a device

SYNOPSIS
       blkdiscard [options] [-o offset] [-l length] device

DESCRIPTION
       blkdiscard  is  used  to	 discard  device  sectors.  This is useful for
       solid-state drivers  (SSDs)  and	 thinly-provisioned  storage.	Unlike
       fstrim(8), this command is used directly on the block device.

       By  default, blkdiscard will discard all blocks on the device.  Options
       may be used to  modify  this  behavior  based  on  range	 or  size,  as
       explained below.

       The device argument is the pathname of the block device.

       WARNING: All data in the discarded region on the device will be lost!

OPTIONS
       The  offset  and length 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.

       -o, --offset offset
	      Byte offset into the device from which to start discarding.  The
	      provided value will be aligned to the device sector  size.   The
	      default value is zero.

       -l, --length length
	      The  number  of  bytes  to  discard  (counting from the starting
	      point).  The provided value will be aligned to the device sector
	      size.   If  the  specified  value	 extends  past	the end of the
	      device, blkdiscard will stop at the device size  boundary.   The
	      default value extends to the end of the device.

       -p, --step length
	      The number of bytes to discard within one iteration. The default
	      is to discard all by one ioctl call.

       -s, --secure
	      Perform a secure discard.	 A secure discard is  the  same	 as  a
	      regular  discard	except that all copies of the discarded blocks
	      that were possibly created by garbage collection	must  also  be
	      erased.  This requires support from the device.

       -z, --zeroout
	      Zero-fill rather than discard.

       -v, --verbose
	      Display  the aligned values of offset and length.	 If the --step
	      option is specified, it prints the discard progress  every  sec‐
	      ond.

       -V, --version
	      Display version information and exit.

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

AUTHOR
       Lukas Czerner ⟨lczerner@redhat.com⟩

SEE ALSO
       fstrim(8)

AVAILABILITY
       The  blkdiscard command is part of the util-linux package and is avail‐
       able Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
       linux/⟩.

util-linux			   July 2014			 BLKDISCARD(8)

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