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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 option
              --step specified than it prints discard progress every second.
       -V, --version
              Display version information and exit.
       -h, --help
              Display help text and exit.
AUTHOR
       Lukas Czerner <lczerner AT redhat.com>
SEE ALSO
       fstrim(8)
AVAILABILITY
       The blkdiscard command is part of the util-linux package and is  avail-
       able  Linux  Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux                         July 2014                     BLKDISCARD(8)