Section: System Administration (8)
Updated: July 2014
blkdiscard - discard sectors on a device
is used to discard device sectors. This is useful for solid-state
drivers (SSDs) and thinly-provisioned storage. Unlike
this command is used directly on the block device.
will discard all blocks on the device. Options may be used to modify
this behavior based on range or size, as explained below.
argument is the pathname of the block device.
WARNING: All data in the discarded region on the device will be lost!
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,
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
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.
The blkdiscard command is part of the util-linux package and is available
Linux Kernel Archive