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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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BLKDISCARD(8) System Administration BLKDISCARD(8)
blkdiscard - discard sectors on a device
blkdiscard [options] [-o offset] [-l length] device
blkdiscard is used to discard device sectors. This is useful for
solid-state drives (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!
Since util-linux v2.41, fdisk has the ability to discard sectors
on both partitions and unpartitioned areas using the 'T' command.
Additionally, sfdisk has the option --discard-free to discard
unpartitioned areas.
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.
-q, --quiet
Suppress warning messages.
-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.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
blkdiscard has the following exit status values:
0
success
1
failure; incorrect invocation, permissions or any other
generic error
2
failure; since v2.39, the device does not support discard
operation
Lukas Czerner <lczerner@redhat.com>, Karel Zak <kzak@redhat.com>
fstrim(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The blkdiscard command is part of the util-linux package which can
be downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
util-linux 2.42-start-521-ec46 2025-08-09 BLKDISCARD(8)
Pages that refer to this page: fstrim(8), sfdisk(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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