blockdev man page

blockdev — call block device ioctls from the command line

Synopsis

blockdev [-q] [-v] command [command...] device [device...]
blockdev --report [device...]

Description

The utility blockdev allows one to call block device ioctls from the command line.

Options

-V
Print version and exit.
-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.

Commands

It is possible to give multiple devices and multiple commands.

--flushbufs
Flush buffers.
--getalignoff
Get alignment offset.
--getbsz
Print blocksize in bytes.
--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 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 like --setra on 2.6 kernels).
--setra sectors
Set readahead (in 512-byte sectors).
--setro
Set read-only.
--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 ftp://ftp.kernel.org/pub/linux/utils/ut….

Referenced By

guestfish(1), guestfs(3), mount(8), salt(7), scsi_ch_swp(8).

August 2010 util-linux System Administration