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       sgmodetool  -  display  and  edit  Mode  Pages  for SCSI, Fibre Channel
       devices accessed using the Linux SG subsystem.

       sgmodetool [-D] [-B Byte from Start of Page] [-P Page  No.]   [-F  Ref.
       Field No.]  [-V New Field/Byte Value] [-o Output LogFile] -d Device

       sgmodetool  is an interactive utility for scsi disks accessed using the
       Linux SG driver. It sends a Mode Sense(6) command to the device to  get
       the  modepages,  displays  them in a tabular format, allows the user to
       change various fields in those pages and then sends  a  Mode  Select(6)
       command  to the device to save the changed modepages.  More information
       about the Mode Sense(6) and Mode Select(6) commands can be found in the
       SCSI Primary Commands-2 (SPC-2) reference documents.

       In  the  interactive  mode sgmodetool is invoked with the -d devicename
       option.  A logfile to store modepage modifications should also be spec-
       ified using the -o logfile option. For example :

       sgmodetool -d /dev/sg3 -o target3.log

       If  a  logfile  is not specified, modepage changes are stored in sgmod-
       etool.log in the current working directory of the user.  The logfile is
       intended  to  facilitate  the  user to make the same change on multiple
       devices (all supporting the   modepages  being  edited).   For  example
       (assuming the logfile is target70.log):

       sh target3.log /dev/sg4

       will copy the modepage changes made on /dev/sg3 to /dev/sg4.

       -P  Page No.
              specifies the number of the modepage to be edited.  Both decimal
              and hex values (preceded by 0x) are acceptable.

       -F  Ref. Field No.
              Specifies the Reference no. of the modepage field being  edited.
              Cannot  be used with the -B option.  Both decimal and hex values
              (preceded by 0x) are acceptable.

       -V  Value
              The new value to be placed in the specified  field/byte  of  the
              page.   Both decimal and hex values (preceded by 0x) are accept-

       -B  Byte No.
              Specifies the byte no. from the start of the  page.   Bytes  are
              numbered  starting from 0 and include the bytes forming the page
              header.  This option cannot be used with the  -F  option.   Both
              decimal and hex values (preceded by 0x) are acceptable.

       -D     Load  Default  Values. This option changes the current values in
              the modepage ( specified using -P ) to their default values.

       In the interactive mode an invalid choice results in the default option
       (specified in []) being chosen. For example :

       Do you wish to modify this ModePage (y/n) ?  [n] :

       Any  keystroke  other  than 'y' or 'Y' will result in 'n' being chosen.
       Modepage changes can result in loss of system data  and  this  facility
       ensures that the user is fully aware of the changes being made.

       1) sgmodetool -P 0x1 -F 16 -V 0x1024 -d <device>

       In this example Field 16 (in the tabular representation) of Page 1 gets
       changed to 0x1024.

       2) sgmodetool -P 0x1 -B 16 -V 0x24 -d <device>

       In this example the 16th byte of Page 1 gets changed to 0x24.

       3) sgmodetool -P 0x1 -D -d <device>

       In this example the current values of ModePage 1 are changed  to  their
       default values.

       /dev/sg* - the Linux SG driver device

       sgformat(8), sgdisktest(8).

       This  command  is  normally  usable  only by the superuser, because the
       standard permissions of the devices in /dev restrict  access  to  other

   Enable Write Caching
       sgmodetool  can be used to set the Write Cache Enable (WCE) bit on scsi
       or fibre channel drives. To enable write caching on these  drives,  the
       following command line can typically be used :

       sgmodetool -P 0x8 -F 8 -V 0x1 -d <device>

       This command line assumes that the drive implements Modepage 8 (Caching
       Parameters). The WCE bit is the 8th field (in the  tabular  representa-
       tion) of Page 8.

       If your drive does not implement Modepage 8, please refer to it's docu-
       mentation to find an alternate location for the Write Cache Enable bit.


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