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 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 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 applies 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/.