dm-linear

设备映射器的“线性”目标将设备映射器设备的线性范围映射到另一个设备的线性范围。这是逻辑卷管理器的基本构建块。

参数：<dev path> <offset>

<dev path>

底层块设备的完整路径名，或“主:次”设备号。

<offset>

设备内的起始扇区。

示例脚本

#!/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`;