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/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/>.