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1=========2dm-linear3=========4 5Device-Mapper's "linear" target maps a linear range of the Device-Mapper6device onto a linear range of another device. This is the basic building7block of logical volume managers.8 9Parameters: <dev path> <offset>10 <dev path>:11 Full pathname to the underlying block-device, or a12 "major:minor" device-number.13 <offset>:14 Starting sector within the device.15 16 17Example scripts18===============19 20::21 22 #!/bin/sh23 # Create an identity mapping for a device24 echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity25 26::27 28 #!/bin/sh29 # Join 2 devices together30 size1=`blockdev --getsz $1`31 size2=`blockdev --getsz $2`32 echo "0 $size1 linear $1 033 $size1 $size2 linear $2 0" | dmsetup create joined34 35::36 37 #!/usr/bin/perl -w38 # Split a device into 4M chunks and then join them together in reverse order.39 40 my $name = "reverse";41 my $extent_size = 4 * 1024 * 2;42 my $dev = $ARGV[0];43 my $table = "";44 my $count = 0;45 46 if (!defined($dev)) {47 die("Please specify a device.\n");48 }49 50 my $dev_size = `blockdev --getsz $dev`;51 my $extents = int($dev_size / $extent_size) -52 (($dev_size % $extent_size) ? 1 : 0);53 54 while ($extents > 0) {55 my $this_start = $count * $extent_size;56 $extents--;57 $count++;58 my $this_offset = $extents * $extent_size;59 60 $table .= "$this_start $extent_size linear $dev $this_offset\n";61 }62 63 `echo \"$table\" | dmsetup create $name`;64