DISKSIM(8)                                             DISKSIM(8)

          disksim - disk simulator

          aux/disksim [ -r ] [ -f file ] [ -s srvname ] [ -m mtpt ] [
          diskname ]

          Disksim presents an in-memory disk in the manner of the
          sd(3) device on mtpt/diskname (default /dev/sdXX).  The disk
          is initialized to zeros; non-zeroed blocks written to the
          disk are kept in memory.

          When setting disk geometry with the geometry control mes-
          sage, the arguments are sectors, sector size, cylinders,
          heads, and sectors per track.  The last three may be zero
          for LBA disk simulations, but must be present.

          The -f option causes disksim to use file as the initial con-
          tents of the disk rather than a zeroed image.  Changes made
          to the disk are written back to file unless the -r option is

          The -s option causes disksim to post its 9P service at

          Disksim can be used to test programs such as fdisk and
          prep(8) that expect sd(3) disks:

               echo geometry 40000 512 0 0 0 >/dev/sdXX/ctl # 20MB
               disk/mbr /dev/sdXX/data
               disk/fdisk -baw /dev/sdXX/data
               disk/prep /dev/sdXX/plan9

          Disksim is useful for creating very large but mostly zeroed
          files for testing other programs.  Test tar(1)'s handling of
          large files:

               for(i in sdXX sdYY sdZZ) aux/disksim $i
               echo geometry 40000000 512 0 0 0 >/dev/sdXX/ctl # 20GB
               echo geometry 10000000 512 0 0 0 >/dev/sdYY/ctl # 5GB
               echo geometry 20000000 512 0 0 0 >/dev/sdZZ/ctl # 10GB
               tar cf /dev/sdXX/data /dev/sdYY/data /dev/sdZZ/data
               tar tvf /dev/sdXX/data


     DISKSIM(8)                                             DISKSIM(8)

          sd(3), prep(8)