blkdiscard(8) — Linux manual page


BLKDISCARD(8)               System Administration              BLKDISCARD(8)

NAME         top

       blkdiscard - discard sectors on a device

SYNOPSIS         top

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

DESCRIPTION         top

       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         top

       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.

       -f, --force
              Disable all checking.  Since v2.36 the block device is open in
              exclusive mode (O_EXCL) by default to avoid collision with
              mounted filesystem or another kernel subsystem.  The force
              option disables the exclusive access mode.

       -o, --offset offset
              Byte offset into the device from which to start discarding.
              The provided value must 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 must 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 second.

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

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

AUTHORS         top

       Lukas Czerner ⟨⟩

SEE ALSO         top


AVAILABILITY         top

       The blkdiscard command is part of the util-linux package and is
       available Linux Kernel Archive 

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found at 
       ⟨⟩.  If you have a
       bug report for this manual page, send it to  This page was obtained from the
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       ⟨git://⟩ on
       2020-06-09.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-06-08.)  If you discover any
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       (which is not part of the original manual page), send a mail to

util-linux                        July 2014                    BLKDISCARD(8)

Pages that refer to this page: fstrim(8)