.TH SCSI_CH_SWP "8" "May 2013" "sdparm\-1.08" SDPARM
.SH NAME
scsi_ch_swp \- change SCSI Software WRITE Protect and block device settings
.SH SYNOPSIS
.B scsi_ch_swp
[\fI\-\-help\fR] [\fI\-\-set 0|1\fR] [\fI\-\-verbose\fR] [\fI\-\-wr\fR]
\fIBLK_DEVICE\fR 
.SH DESCRIPTION
.\" Add any additional description here
.PP
This bash shell script attempts to read or change the Software Write
Protect (SWP) bit in the SCSI Control mode page using the sdparm utility.
If that change is successful then it uses the blockdev utility to change
\fIBLK_DEVICE\fR's read\-write or read\-only setting in sympathy. This
script is only available in Linux since the blockdev utility is Linux
specific.
.PP
If changing the SWP bit is supported, setting the SWP bit makes
\fIBLK_DEVICE\fR read\-only at the device (disk) itself. Clearing the SWP
bit makes \fIBLK_DEVICE\fR read\-write which is usually the default
setting at device (disk) power up.
.PP
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 \fIBLK_DEVICE\fR is in read\-only mode; if they are both 0 then
\fIBLK_DEVICE\fR is in read\-write mode.
.SH OPTIONS
Arguments to long options are mandatory for short options as well.
.TP
\fB\-h\fR, \fB\-\-help\fR
print out the usage message then exit.
.TP
\fB\-s\fR, \fB\-\-set\fR \fI0|1\fR
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 \fIBLK_DEVICE\fR
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 \fIBLK_DEVICE\fR to
read\-only mode. The default (i.e. when this option is not given) is to read
the state of the SWP bit and \fIBLK_DEVICE\fR's read\-only mode and print
those values out.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
increase level or verbosity.
.TP
\fB\-w\fR, \fB\-\-wr\fR
when the \fIBLK_DEVICE\fR is in read\-only mode, Linux will not typically
allow \fIBLK_DEVICE\fR to be opened read\-write by sdparm, so the default
action of this script is to use the sdparm \fI\-\-readonly\fR option when
\fI\-\-set 0\fR has been invoked. It is possible that \fIBLK_DEVICE\fR 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 \fI\-\-wr\fR
option makes sdparm open \fIBLK_DEVICE\fR read\-write when \fI\-\-set 0\fR
is invoked. 
.SH 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, whichever is called
last. See the sdparm(8) man page.
.SH AUTHORS
Written by D. Gilbert
.SH COPYRIGHT
Copyright \(co 2013 Douglas Gilbert
.br
This software is distributed under a FreeBSD license. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
.B sdparm(sdparm), blockdev(8)