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 https://www.kernel.org/pub/linux/utils/util-linux/.

Referenced By

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

August 2010 util-linux System Administration