scsi_ch_swp(8)

1SCSI_CH_SWP(8)                      SDPARM                      SCSI_CH_SWP(8)
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NAME

6       scsi_ch_swp  - change SCSI Software WRITE Protect and block device set‐
7       tings
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SYNOPSIS

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

13       This bash shell script attempts to read or change  the  Software  Write
14       Protect  (SWP) bit in the SCSI Control mode page using the sdparm util‐
15       ity.  If that change is successful then it uses the blockdev utility to
16       change  BLK_DEVICE's  read-write or read-only setting in sympathy. This
17       script is only available in Linux since the blockdev utility  is  Linux
18       specific.
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20       If  changing  the  SWP  bit  is  supported,  setting  the SWP bit makes
21       BLK_DEVICE read-only at the device (disk) itself. Clearing the SWP  bit
22       makes  BLK_DEVICE  read-write  which  is usually the default setting at
23       device (disk) power up.
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25       If no options are given then the  current  state  of  the  SWP  bit  is
26       printed out (using sdparm) together with blockdev's RO bit. If they are
27       both 1 then BLK_DEVICE is in read-only mode; if they are  both  0  then
28       BLK_DEVICE is in read-write mode.
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OPTIONS

31       Arguments to long options are mandatory for short options as well.
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33       -h, --help
34              print out the usage message then exit.
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36       -s, --set 0|1
37              when  0  is  given  then the SWP bit in the Control mode page is
38              cleared (i.e.  set that bit to 0) using sdparm; and blockdev  is
39              used  to set BLK_DEVICE to read-write mode. When 1 is given then
40              the SWP bit in the Control mode page is set  using  sdparm;  and
41              blockdev  is  used  to  set  BLK_DEVICE  to  read-only mode. The
42              default (i.e. when this option is not  given)  is  to  read  the
43              state  of  the SWP bit and BLK_DEVICE's read-only mode and print
44              those values out.
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46       -v, --verbose
47              increase level or verbosity.
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49       -w, --wr
50              when the BLK_DEVICE is in read-only mode, Linux will  not  typi‐
51              cally allow BLK_DEVICE to be opened read-write by sdparm, so the
52              default action of this script is to use  the  sdparm  --readonly
53              option  when  --set  0  has  been  invoked.  It is possible that
54              BLK_DEVICE could be a generic device (e.g. /dev/sg3) which has a
55              different  interpretation  of  the  read-only  open flag and may
56              fail. For such rare cases the  --wr  option  makes  sdparm  open
57              BLK_DEVICE read-write when --set 0 is invoked.
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EXIT STATUS

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

65       Written by D. Gilbert
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COPYRIGHT

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