About the volume header: one solution

[Shoshana Abrass]

Dave Olsen (olson at anchor.esd.sgi.com) writes:

>> |   I'm writing my own version of 'hinv'. Having the disk serial #'s appear 
>> |   in the listing would be VERY useful.
>> 
>> You can certainly do this, but if you call it hinv, you may break
>> SGI programs that use it and expect known output.  If you must
>> call it hinv, put it in /usr/local/bin, or something like that.

  I was speaking euphemistically. The program I'm writing has the basic 
  functionality of hinv but will not be used the same way, and certainly
  won't have the same name. I guess I sounded stupider than I like to 
  think :).

>> The sgilabel file has the serial number in it for some disks, and
>> the input is pretty free form. 

  I looked at the sgilabel once (using dvhtool to get it into a file) and
  all I know is that it wasn't an ascii file, and I rated my chances of
  getting the file format out of the Hotline to be close to nil.

>> ... the volhdr only has room for 16 files, so make sure you
>> don't put too many files there.  In particular, inst puts a temporary
>> file there during miniroot installs.

  This is good to know, though we're not anywhere close to 15 files yet.
  I'll leave room for inst.

>> You could simply get the file out with 'dvhtool -v g vhfile file'
>> if you are doing a shell script.  Otherwise look at sys/dkio.h
>> and sys/dvh.h.  

  I am *not* writing a shell script. I must have sounded *really* stupid.
  Why would I write a shell script to replace hinv?  Anyway, I will
  (hopefully) make up for the shortcomings of my question by posting
  the answer. By the way, I understand that this was discussed a few
  months ago - sorry to repeat a recent topic, but I was off the list
  for a while.

  This is a fragment from a program that uses the volume header to read 
  the partition table. Finding all the necessary include files is left
  as an exercise to the reader :). I do not guarantee that this is the
  best way to tackle this problem.


read_partition_table(char* file)               <=== "file" is a disk path
{                                                   e.g., /dev/rdsk/dks0d1vh
   
    int      fd;
    struct   volume_header  *buf;

    buf = (struct volume_header *)malloc(512);<===  Seems like there should be
                                                    some explanation of how
                                                    this number was calculated
    if ( (fd = open(file, O_RDONLY)) == -1 ) {
        perror(file);
        return(0);
    }

    if ( (ioctl(fd, DIOCGETVH, buf)) == -1 ) {
        perror(file);
        return(0);
    }

    /* buf is now a pointer to the volume header data */
    /* Do whatever you want with the volume header here... */
}

-------------
  -shoshana
   shoshana at pdi.com