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SCSI_CH_SWP(8)			    SDPARM			SCSI_CH_SWP(8)

NAME
       scsi_ch_swp  - change SCSI Software WRITE Protect and block device set‐
       tings

SYNOPSIS
       scsi_ch_swp [--help] [--set 0|1] [--verbose] [--wr] BLK_DEVICE

DESCRIPTION
       This bash shell script attempts to read or change  the  Software	 Write
       Protect	(SWP) bit in the SCSI Control mode page using the sdparm util‐
       ity.  If that change is successful then it uses the blockdev utility to
       change  BLK_DEVICE's  read-write or read-only setting in sympathy. This
       script is only available in Linux since the blockdev utility  is	 Linux
       specific.

       If  changing  the  SWP  bit  is	supported,  setting  the SWP bit makes
       BLK_DEVICE read-only at the device (disk) itself. Clearing the SWP  bit
       makes  BLK_DEVICE  read-write  which  is usually the default setting at
       device (disk) power up.

       If no options are given then the	 current  state	 of  the  SWP  bit  is
       printed out (using sdparm) together with blockdev's RO bit. If they are
       both 1 then BLK_DEVICE is in read-only mode; if they are	 both  0  then
       BLK_DEVICE is in read-write mode.

OPTIONS
       Arguments to long options are mandatory for short options as well.

       -h, --help
	      print out the usage message then exit.

       -s, --set 0|1
	      when  0  is  given  then the SWP bit in the Control mode page is
	      cleared (i.e.  set that bit to 0) using sdparm; and blockdev  is
	      used  to set BLK_DEVICE to read-write mode. When 1 is given then
	      the SWP bit in the Control mode page is set  using  sdparm;  and
	      blockdev	is  used  to  set  BLK_DEVICE  to  read-only mode. The
	      default (i.e. when this option is not  given)  is	 to  read  the
	      state  of	 the SWP bit and BLK_DEVICE's read-only mode and print
	      those values out.

       -v, --verbose
	      increase level or verbosity.

       -w, --wr
	      when the BLK_DEVICE is in read-only mode, Linux will  not	 typi‐
	      cally allow BLK_DEVICE to be opened read-write by sdparm, so the
	      default action of this script is to use  the  sdparm  --readonly
	      option  when  --set  0  has  been	 invoked.  It is possible that
	      BLK_DEVICE could be a generic device (e.g. /dev/sg3) which has a
	      different	 interpretation	 of  the  read-only  open flag and may
	      fail. For such rare cases the  --wr  option  makes  sdparm  open
	      BLK_DEVICE read-write when --set 0 is invoked.

EXIT STATUS
       The  exit  status  of this script is 0 when it is successful. Otherwise
       the exit status is that of the sdparm or the blockdev  utility,	which‐
       ever is called last. See the sdparm(8) man page.

AUTHORS
       Written by D. Gilbert

COPYRIGHT
       Copyright © 2013 Douglas Gilbert
       This  software is distributed under a FreeBSD license. There is NO war‐
       ranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PUR‐
       POSE.

SEE ALSO
       sdparm(sdparm), blockdev(8)

sdparm-1.08			   May 2013			SCSI_CH_SWP(8)

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