0001 =========
0002 dm-linear
0003 =========
0004
0005 Device-Mapper's "linear" target maps a linear range of the Device-Mapper
0006 device onto a linear range of another device. This is the basic building
0007 block of logical volume managers.
0008
0009 Parameters: <dev path> <offset>
0010 <dev path>:
0011 Full pathname to the underlying block-device, or a
0012 "major:minor" device-number.
0013 <offset>:
0014 Starting sector within the device.
0015
0016
0017 Example scripts
0018 ===============
0019
0020 ::
0021
0022 #!/bin/sh
0023 # Create an identity mapping for a device
0024 echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity
0025
0026 ::
0027
0028 #!/bin/sh
0029 # Join 2 devices together
0030 size1=`blockdev --getsz $1`
0031 size2=`blockdev --getsz $2`
0032 echo "0 $size1 linear $1 0
0033 $size1 $size2 linear $2 0" | dmsetup create joined
0034
0035 ::
0036
0037 #!/usr/bin/perl -w
0038 # Split a device into 4M chunks and then join them together in reverse order.
0039
0040 my $name = "reverse";
0041 my $extent_size = 4 * 1024 * 2;
0042 my $dev = $ARGV[0];
0043 my $table = "";
0044 my $count = 0;
0045
0046 if (!defined($dev)) {
0047 die("Please specify a device.\n");
0048 }
0049
0050 my $dev_size = `blockdev --getsz $dev`;
0051 my $extents = int($dev_size / $extent_size) -
0052 (($dev_size % $extent_size) ? 1 : 0);
0053
0054 while ($extents > 0) {
0055 my $this_start = $count * $extent_size;
0056 $extents--;
0057 $count++;
0058 my $this_offset = $extents * $extent_size;
0059
0060 $table .= "$this_start $extent_size linear $dev $this_offset\n";
0061 }
0062
0063 `echo \"$table\" | dmsetup create $name`;
