BLOCKDEV(8) System Administration BLOCKDEV(8)
NAME
blockdev - call block device ioctls from the command line
SYNOPSIS
blockdev [-q] [-v] command [command...] device [device...]
blockdev --report [device...]
blockdev -h|-V
DESCRIPTION
The utility blockdev allows one to call block device ioctls from the
command line.
OPTIONS
-q
Be quiet.
-v
Be verbose.
--report
Print a report for the specified device. It is possible to give
multiple devices. If none is given, all devices which appear in
/proc/partitions are shown. Note that the partition StartSec is in
512-byte sectors.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
COMMANDS
It is possible to give multiple devices and multiple commands.
--flushbufs
Flush buffers.
--getalignoff
Get alignment offset.
--getbsz
Print the blocksize in bytes. This size does not describe device
topology. It’s the size used internally by the kernel and it may be
modified (for example) by filesystem driver on mount.
--getdiscardzeroes
Get discard zeroes support status.
--getdiskseq
Get disk sequence number.
--getzonesz
Get zone size in 512-byte sectors.
--getfra
Get filesystem readahead in 512-byte sectors.
--getiomin
Get minimum I/O size.
--getioopt
Get optimal I/O size.
--getmaxsect
Get max sectors per request.
--getpbsz
Get physical block (sector) size.
--getra
Print readahead (in 512-byte sectors).
--getro
Get read-only. Print 1 if the device is read-only, 0 otherwise.
--getsize64
Print device size in bytes.
--getsize
Print device size (32-bit!) in sectors. Deprecated in favor of the
--getsz option.
--getss
Print logical sector size in bytes - usually 512.
--getsz
Get size in 512-byte sectors.
--rereadpt
Reread partition table.
--setbsz bytes
Set blocksize. Note that the block size is specific to the current
file descriptor opening the block device, so the change of block
size only persists for as long as blockdev has the device open, and
is lost once blockdev exits.
--setfra sectors
Set filesystem readahead (same as --setra on 2.6 kernels).
--setra sectors
Set readahead (in 512-byte sectors).
--setro
Set read-only. The currently active access to the device may not be
affected by the change. For example, a filesystem already mounted in
read-write mode will not be affected. The change applies after
remount.
--setrw
Set read-write.
AUTHORS
blockdev was written by Andries E. Brouwer and rewritten by Karel Zak.
REPORTING BUGS
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
AVAILABILITY
The blockdev 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/>.
util-linux 2.41 2025-02-26 BLOCKDEV(8)
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