Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.
1 dm-linear 2 ========= 3 4 Device-Mapper's "linear" target maps a linear range of the Device-Mapper 5 device onto a linear range of another device. This is the basic building 6 block of logical volume managers. 7 8 Parameters: <dev path> <offset> 9 <dev path>: Full pathname to the underlying block-device, or a 10 "major:minor" device-number. 11 <offset>: Starting sector within the device. 12 13 14 Example scripts 15 =============== 16 [[ 17 #!/bin/sh 18 # Create an identity mapping for a device 19 echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity 20 ]] 21 22 23 [[ 24 #!/bin/sh 25 # Join 2 devices together 26 size1=`blockdev --getsz $1` 27 size2=`blockdev --getsz $2` 28 echo "0 $size1 linear $1 0 29 $size1 $size2 linear $2 0" | dmsetup create joined 30 ]] 31 32 33 [[ 34 #!/usr/bin/perl -w 35 # Split a device into 4M chunks and then join them together in reverse order. 36 37 my $name = "reverse"; 38 my $extent_size = 4 * 1024 * 2; 39 my $dev = $ARGV[0]; 40 my $table = ""; 41 my $count = 0; 42 43 if (!defined($dev)) { 44 die("Please specify a device.\n"); 45 } 46 47 my $dev_size = `blockdev --getsz $dev`; 48 my $extents = int($dev_size / $extent_size) - 49 (($dev_size % $extent_size) ? 1 : 0); 50 51 while ($extents > 0) { 52 my $this_start = $count * $extent_size; 53 $extents--; 54 $count++; 55 my $this_offset = $extents * $extent_size; 56 57 $table .= "$this_start $extent_size linear $dev $this_offset\n"; 58 } 59 60 `echo \"$table\" | dmsetup create $name`; 61 ]]