=========dm-linear========= Device-Mapper's "linear" target maps a linear range of the Device-Mapperdevice onto a linear range of another device.  This is the basic buildingblock of logical volume managers. Parameters: <dev path> <offset>    <dev path>:	Full pathname to the underlying block-device, or a        "major:minor" device-number.    <offset>:	Starting sector within the device.  Example scripts=============== ::   #!/bin/sh  # Create an identity mapping for a device  echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity ::   #!/bin/sh  # Join 2 devices together  size1=`blockdev --getsz $1`  size2=`blockdev --getsz $2`  echo "0 $size1 linear $1 0  $size1 $size2 linear $2 0" | dmsetup create joined ::   #!/usr/bin/perl -w  # Split a device into 4M chunks and then join them together in reverse order.   my $name = "reverse";  my $extent_size = 4 * 1024 * 2;  my $dev = $ARGV[0];  my $table = "";  my $count = 0;   if (!defined($dev)) {          die("Please specify a device.\n");  }   my $dev_size = `blockdev --getsz $dev`;  my $extents = int($dev_size / $extent_size) -                (($dev_size % $extent_size) ? 1 : 0);   while ($extents > 0) {          my $this_start = $count * $extent_size;          $extents--;          $count++;          my $this_offset = $extents * $extent_size;           $table .= "$this_start $extent_size linear $dev $this_offset\n";  }   `echo \"$table\" | dmsetup create $name`;