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
Print version and exit.
COMMANDS
It is possible to give multiple devices and multiple commands.
--flushbufs
Flush buffers.
--getalignoff
Get alignment offset.
--getbsz
Print blocksize in bytes. This size does not describe device
topology. It's size used internally by kernel and it maybe mod-
ified (for example) by filesystem driver on mount.
--getdiscardzeroes
Get discard zeroes support status.
--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 cur-
rent 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 like --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 filesystem already
mounted in read-write mode will not be affected. The change ap-
plies after remount.
--setrw
Set read-write.
AUTHOR
blockdev was written by Andries E. Brouwer and rewritten by Karel Zak.
AVAILABILITY
The blockdev command is part of the util-linux package and is available
from https://www.kernel.org/pub/linux/utils/util-linux/.
util-linux August 2010 BLOCKDEV(8)