1*4882a593Smuzhiyun========= 2*4882a593Smuzhiyundm-linear 3*4882a593Smuzhiyun========= 4*4882a593Smuzhiyun 5*4882a593SmuzhiyunDevice-Mapper's "linear" target maps a linear range of the Device-Mapper 6*4882a593Smuzhiyundevice onto a linear range of another device. This is the basic building 7*4882a593Smuzhiyunblock of logical volume managers. 8*4882a593Smuzhiyun 9*4882a593SmuzhiyunParameters: <dev path> <offset> 10*4882a593Smuzhiyun <dev path>: 11*4882a593Smuzhiyun Full pathname to the underlying block-device, or a 12*4882a593Smuzhiyun "major:minor" device-number. 13*4882a593Smuzhiyun <offset>: 14*4882a593Smuzhiyun Starting sector within the device. 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun 17*4882a593SmuzhiyunExample scripts 18*4882a593Smuzhiyun=============== 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun:: 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun #!/bin/sh 23*4882a593Smuzhiyun # Create an identity mapping for a device 24*4882a593Smuzhiyun echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity 25*4882a593Smuzhiyun 26*4882a593Smuzhiyun:: 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun #!/bin/sh 29*4882a593Smuzhiyun # Join 2 devices together 30*4882a593Smuzhiyun size1=`blockdev --getsz $1` 31*4882a593Smuzhiyun size2=`blockdev --getsz $2` 32*4882a593Smuzhiyun echo "0 $size1 linear $1 0 33*4882a593Smuzhiyun $size1 $size2 linear $2 0" | dmsetup create joined 34*4882a593Smuzhiyun 35*4882a593Smuzhiyun:: 36*4882a593Smuzhiyun 37*4882a593Smuzhiyun #!/usr/bin/perl -w 38*4882a593Smuzhiyun # Split a device into 4M chunks and then join them together in reverse order. 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun my $name = "reverse"; 41*4882a593Smuzhiyun my $extent_size = 4 * 1024 * 2; 42*4882a593Smuzhiyun my $dev = $ARGV[0]; 43*4882a593Smuzhiyun my $table = ""; 44*4882a593Smuzhiyun my $count = 0; 45*4882a593Smuzhiyun 46*4882a593Smuzhiyun if (!defined($dev)) { 47*4882a593Smuzhiyun die("Please specify a device.\n"); 48*4882a593Smuzhiyun } 49*4882a593Smuzhiyun 50*4882a593Smuzhiyun my $dev_size = `blockdev --getsz $dev`; 51*4882a593Smuzhiyun my $extents = int($dev_size / $extent_size) - 52*4882a593Smuzhiyun (($dev_size % $extent_size) ? 1 : 0); 53*4882a593Smuzhiyun 54*4882a593Smuzhiyun while ($extents > 0) { 55*4882a593Smuzhiyun my $this_start = $count * $extent_size; 56*4882a593Smuzhiyun $extents--; 57*4882a593Smuzhiyun $count++; 58*4882a593Smuzhiyun my $this_offset = $extents * $extent_size; 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun $table .= "$this_start $extent_size linear $dev $this_offset\n"; 61*4882a593Smuzhiyun } 62*4882a593Smuzhiyun 63*4882a593Smuzhiyun `echo \"$table\" | dmsetup create $name`; 64