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 ex-
plained 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 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 de-
vice, blkdiscard will stop at the device size boundary. The de-
fault 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)