blockdev - call block device ioctls from the command line
blockdev [-q] [-v] command [command...]
blockdev --report [device...]
The utility blockdev allows one to call block device ioctls from the
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
Display help text and exit.
Print version and exit.
It is possible to give multiple devices and multiple commands.
Get alignment offset.
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.
Get discard zeroes support status.
Get filesystem readahead in 512-byte sectors.
Get minimum I/O size.
Get optimal I/O size.
Get max sectors per request.
Get physical block (sector) size.
Print readahead (in 512-byte sectors).
Get read-only. Print 1 if the device is read-only, 0
Print device size in bytes.
Print device size (32-bit!) in sectors. Deprecated in
favor of the --getsz option.
Print logical sector size in bytes - usually 512.
Get size in 512-byte sectors.
Reread partition table
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.
Set filesystem readahead (same as --setra on 2.6
Set readahead (in 512-byte sectors).
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
blockdev was written by Andries E. Brouwer and rewritten by Karel Zak.