blockdev(8) - man - phpman

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⚡ TLDR: blockdev (tldr-pages)

Manage, query, and manipulate block devices.

Print a report for all devices
sudo blockdev --report
Print a report for a specific device
sudo blockdev --report {{/dev/sdXY}}
Get the size of a device in 512-byte sectors
sudo blockdev --getsz {{/dev/sdXY}}
Set read-only
sudo blockdev --setro {{/dev/sdXY}}
Set read-write
sudo blockdev --setrw {{/dev/sdXY}}
Flush buffers
sudo blockdev --flushbufs {{/dev/sdXY}}
Get the physical block size
sudo blockdev --getpbsz {{/dev/sdXY}}
Set the read-ahead value to 128 sectors
sudo blockdev --setra 128 {{/dev/sdXY}}

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 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.

--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 at https://github.com/karelzak/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 2.37.2 2021-06-02 BLOCKDEV(8)