# blockdev

## 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**
               Display 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.
    
           **--getdiskseq**
               Get disk sequence number.
    
           **--getzonesz**
               Get zone size in 512-byte sectors.
    
           **--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.
    


## 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/>. This page is
           part of the _util-linux_ (a random collection of Linux utilities)
           project. Information about the project can be found at 
           ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
           bug report for this manual page, send it to
           util-linux@vger.kernel.org. This page was obtained from the
           project's upstream Git repository
           ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
           2025-08-11. (At that time, the date of the most recent commit that
           was found in the repository was 2025-08-05.) If you discover any
           rendering problems in this HTML version of the page, or you
           believe there is a better or more up-to-date source for the page,
           or you have corrections or improvements to the information in this
           COLOPHON (which is _not_ part of the original manual page), send a
           mail to man-pages@man7.org
    
    util-linux 2.42-start-521-ec46  2025-08-09                    _BLOCKDEV_(8)
    


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