1. 先查看第一个空闲loop设备
代码:
sudo losetup -f
/dev/loop0
2. 使用上一步得到的设备名，第一次创建loop设备
代码:
sudo losetup /dev/loop0 archlinux-2008.06-core-i686.img
3. 查看信息
代码:
sudo fdisk -lu /dev/loop0
Disk /dev/loop0: 322 MB, 322469376 bytes
53 heads, 12 sectors/track, 990 cylinders, total 629823 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/loop0p1 * 63 629822 314880 83 Linux
Partition 1 has different physical/logical beginnings (non-Linux?):
phys=(0, 1, 1) logical=(0, 5, 4)
Partition 1 has different physical/logical endings:
phys=(39, 52, 12) logical=(990, 15, 3)
我们可以看到，该镜像只有一个分区(loop0p1)，从第63扇区开始(Start列)，每扇区512字节(Units = sectors of 1 * 512 = 512 bytes)，我们算出offset，下面mout命令会用到：
4. mout
代码:
sudo losetup -o 32256 /dev/loop1 archlinux-2008.06-core-i686.img
sudo mount -o loop /dev/loop1 /mnt/
ls /mnt/
addons archlive.sqfs boot lost+found
事实上，fdisk可以直接查看img文件(虽然功能不全，下面会说到)，mount可以自动创建loop设备，所以上面步骤可以简化为：
I. 查看信息
代码:
sudo fdisk -lu archlinux-2008.06-core-i686.img
You must set cylinders.
You can do this from the extra functions menu.
Disk archlinux-2008.06-core-i686.img: 0 MB, 0 bytes
53 heads, 12 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
archlinux-2008.06-core-i686.img1 * 63 629822 314880 83 Linux
Partition 1 has different physical/logical beginnings (non-Linux?):
phys=(0, 1, 1) logical=(0, 5, 4)
Partition 1 has different physical/logical endings:
phys=(39, 52, 12) logical=(990, 15, 3)
第一行抱怨不能得到cylinders，原因是普通文件上没有实现ioctl操作，我们可以看到0 cylinders，但这对我们不重要，关键是我们依然可以得到第一个分区（archlinux-2008.06-core-i686.img1）的偏移值
II. 直接mount
代码:
sudo mount -o loop,offset=32256 archlinux-2008.06-core-i686.img /mnt/
ls /mnt/
addons archlive.sqfs boot lost+found
参考
Loop-mounting partitions from a disk image
08-08-08, 19:56
