dm-linear

Device-Mapper 的“線性（linear）”目標將 Device-Mapper 裝置的一個線性範圍對映到另一個裝置的線性範圍。這是邏輯卷管理器的基本構建塊。

引數: <dev path> <offset>

<dev path>

底層塊裝置的完整路徑名，或“主裝置號:次裝置號”的裝置號。

<offset>

裝置內的起始扇區。

示例指令碼

#!/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`;