blkdiscard <root
BLKDISCARD(8)                         System Administration                         BLKDISCARD(8)

NAME
       blkdiscard - discard sectors on a device

SYNOPSIS
       blkdiscard [-o offset] [-l length] [-s] [-v] 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 mod‐
       ify 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 col‐
              lection must also be erased.  This requires support from the device.

       -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@redhat.com⟩

SEE ALSO
       fstrim(8)

AVAILABILITY
       The  blkdiscard  command  is  part of the util-linux package and is available Linux Kernel
       Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-linux/⟩.

util-linux                                  July 2014                               BLKDISCARD(8)

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