如何挂载一个镜像文件(how to mount an image file)

如何挂载一个镜像文件(how to mount an image file)

08/16/2012master 4 Comments
在使用KVM或Xen虚拟化的情况下，经常需要使用镜像文件（image file），我们可以将Guest系统启动起来，然后对镜像文件进行修改，不过这样有时也是比较麻烦，其实也是可以将镜像文件直接进行mount的，可以用如下两种办法。

（本文写的RAW格式镜像文件的挂载；我的另一篇文章写了“如何挂载qcow2格式的镜像文件”）

方法一：找出分区开始的开始位置，使用mount命令的offset参数偏移掉前面不需要的，即可得到真正的分区。其具体步骤如下：

1. 用“fdisk -lu my.img”查询image信息；

2. 计算image内分区开始的地方（计算offset），用从N号sector（扇区）开始，则offset=N*M （M为一个sector的大小，一般为512）

3. 使用mount命令挂载为loop设备即可。 （如LVM分区，则会较复杂，请见本文最后的介绍）

在Linux系统上具体操作演示如下：

[root@jay-linux image]# fdisk -lu rhel6u2.img
You must set cylinders.
You can do this from the extra functions menu.

Disk rhel6u2.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00048b34

Device Boot Start End Blocks Id System
rhel6u2.img1 * 2048 1026047 512000 83 Linux
Partition 1 does not end on cylinder boundary.
rhel6u2.img2 1026048 104857599 51915776 8e Linux LVM
Partition 2 has different physical/logical endings:
phys=(1023, 254, 63) logical=(6527, 21, 22)
[root@jay-linux image]# echo $((2048*512))
1048576
[root@jay-linux image]# mount -o loop,offset=1048576 rhel6u2.img /media/
[root@jay-linux image]# cd /media/
[root@jay-linux media]# ls
config-2.6.32-220.el6.x86_64 initramfs-3.5.0.img System.map-2.6.32-279.el6.x86_64
config-2.6.32-279.el6.x86_64 lost+found System.map-3.5.0
efi symvers-2.6.32-220.el6.x86_64.gz vmlinuz
grub symvers-2.6.32-279.el6.x86_64.gz vmlinuz-2.6.32-220.el6.x86_64
initramfs-2.6.32-220.el6.x86_64.img System.map vmlinuz-2.6.32-279.el6.x86_64
initramfs-2.6.32-279.el6.x86_64.img System.map-2.6.32-220.el6.x86_64 vmlinuz-3.5.0
[root@jay-linux media]# echo $((1026048*512))
525336576
[root@jay-linux media]# umount /media
[root@jay-linux media]# cd /home/image/
[root@jay-linux image]# umount /media
[root@jay-linux image]# mount -o loop,offset=525336576 rhel6u2.img /media/
mount: unknown filesystem type 'LVM2_member'
（镜像文件中的LVM分区mount的问题，本文最后单独说明）

[root@jay-linux image]# fdisk -lu sles11sp2-i386.img
You must set cylinders.
You can do this from the extra functions menu.

Disk sles11sp2-i386.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0002d3be

Device Boot Start End Blocks Id System
sles11sp2-i386.img1 2048 4208639 2103296 82 Linux swap / Solaris
Partition 1 does not end on cylinder boundary.
sles11sp2-i386.img2 * 4208640 41943039 18867200 83 Linux
Partition 2 has different physical/logical endings:
phys=(1023, 254, 63) logical=(2610, 212, 34)
[root@jay-linux image]# echo $((4208640*512))
2154823680
[root@jay-linux image]# mount -o loop,offset=2154823680 sles11sp2-i386.img /media
[root@jay-linux image]# cd /media/
[root@jay-linux media]# ls
bin dev home lost+found mnt proc sbin srv sys usr
boot etc lib media opt root selinux success tmp var
[root@jay-linux image]# umount /media/

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

[root@jay-linux image]# fdisk -lu rhel6u2.img You must set cylinders. You can do this from the extra functions menu. Disk rhel6u2.img: 0 MB, 0 bytes 255 heads, 63 sectors/track, 0 cylinders, total 0 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00048b34 Device Boot Start End Blocks Id System rhel6u2.img1 * 2048 1026047 512000 83 Linux Partition 1 does not end on cylinder boundary. rhel6u2.img2 1026048 104857599 51915776 8e Linux LVM Partition 2 has different physical/logical endings: phys=(1023, 254, 63) logical=(6527, 21, 22) [root@jay-linux image]# echo $((2048*512)) 1048576 [root@jay-linux image]# mount -o loop,offset=1048576 rhel6u2.img /media/ [root@jay-linux image]# cd /media/ [root@jay-linux media]# ls config-2.6.32-220.el6.x86_64 initramfs-3.5.0.img System.map-2.6.32-279.el6.x86_64 config-2.6.32-279.el6.x86_64 lost+found System.map-3.5.0 efi symvers-2.6.32-220.el6.x86_64.gz vmlinuz grub symvers-2.6.32-279.el6.x86_64.gz vmlinuz-2.6.32-220.el6.x86_64 initramfs-2.6.32-220.el6.x86_64.img System.map vmlinuz-2.6.32-279.el6.x86_64 initramfs-2.6.32-279.el6.x86_64.img System.map-2.6.32-220.el6.x86_64 vmlinuz-3.5.0 [root@jay-linux media]# echo $((1026048*512)) 525336576 [root@jay-linux media]# umount /media [root@jay-linux media]# cd /home/image/ [root@jay-linux image]# umount /media [root@jay-linux image]# mount -o loop,offset=525336576 rhel6u2.img /media/ mount: unknown filesystem type 'LVM2_member' （镜像文件中的LVM分区mount的问题，本文最后单独说明） [root@jay-linux image]# fdisk -lu sles11sp2-i386.img You must set cylinders. You can do this from the extra functions menu. Disk sles11sp2-i386.img: 0 MB, 0 bytes 255 heads, 63 sectors/track, 0 cylinders, total 0 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0002d3be Device Boot Start End Blocks Id System sles11sp2-i386.img1 2048 4208639 2103296 82 Linux swap / Solaris Partition 1 does not end on cylinder boundary. sles11sp2-i386.img2 * 4208640 41943039 18867200 83 Linux Partition 2 has different physical/logical endings: phys=(1023, 254, 63) logical=(2610, 212, 34) [root@jay-linux image]# echo $((4208640*512)) 2154823680 [root@jay-linux image]# mount -o loop,offset=2154823680 sles11sp2-i386.img /media [root@jay-linux image]# cd /media/ [root@jay-linux media]# ls bin dev home lost+found mnt proc sbin srv sys usr boot etc lib media opt root selinux success tmp var [root@jay-linux image]# umount /media/

方法二：用kpartx建立分区映射后，再mount映射后的设备即可，操作实例如下：

[root@jay-linux image]# kpartx -av sles11sp2-i386.img
add map loop3p1 (253:2): 0 4206592 linear /dev/loop3 2048
add map loop3p2 (253:3): 0 37734400 linear /dev/loop3 4208640

[root@jay-linux image]# mount /dev/mapper/loop3p2 /media/

[root@jay-linux image]# ls /media/
bin dev home lost+found mnt proc sbin srv sys usr
boot etc lib media opt root selinux success tmp var
[root@jay-linux image]# umount /media/
[root@jay-linux image]# mount /dev/mapper/loop3p1 /media/
/dev/mapper/loop3p1 looks like swapspace - not mounted
mount: you must specify the filesystem type
（其中的交换分区，我也还不知道是否可以mount；其实mount交换分区也没意义）

（使用完成后，卸载挂载点、删除映射关系即可）
[root@jay-linux image]# umount /media/
[root@jay-linux image]# kpartx -d sles11sp2-i386.img
loop deleted : /dev/loop3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

[root@jay-linux image]# kpartx -av sles11sp2-i386.img add map loop3p1 (253:2): 0 4206592 linear /dev/loop3 2048 add map loop3p2 (253:3): 0 37734400 linear /dev/loop3 4208640 [root@jay-linux image]# mount /dev/mapper/loop3p2 /media/ [root@jay-linux image]# ls /media/ bin dev home lost+found mnt proc sbin srv sys usr boot etc lib media opt root selinux success tmp var [root@jay-linux image]# umount /media/ [root@jay-linux image]# mount /dev/mapper/loop3p1 /media/ /dev/mapper/loop3p1 looks like swapspace - not mounted mount: you must specify the filesystem type （其中的交换分区，我也还不知道是否可以mount；其实mount交换分区也没意义） （使用完成后，卸载挂载点、删除映射关系即可） [root@jay-linux image]# umount /media/ [root@jay-linux image]# kpartx -d sles11sp2-i386.img loop deleted : /dev/loop3

关于LVM的mount，可以参考文末参考资料中的vpsee的文章（我也是试多次没做成功，才偶然看到这篇文章的），我对镜像文件中LVM分区的mount操作如下供参考。

[root@jay-linux image]# fdisk -lu rhel6u2.img
You must set cylinders.
You can do this from the extra functions menu.

Disk rhel6u2.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00048b34

Device Boot Start End Blocks Id System
rhel6u2.img1 * 2048 1026047 512000 83 Linux
Partition 1 does not end on cylinder boundary.
rhel6u2.img2 1026048 104857599 51915776 8e Linux LVM
Partition 2 has different physical/logical endings:
phys=(1023, 254, 63) logical=(6527, 21, 22)
[root@jay-linux image]# echo $((1026048*512))
525336576
[root@jay-linux image]# losetup /dev/loop0 rhel6u2.img -o 525336576
[root@jay-linux image]# pvscan
PV /dev/loop0 VG VolGroup lvm2 [49.51 GiB / 0 free]
Total: 1 [49.51 GiB] / in use: 1 [49.51 GiB] / in no VG: 0 [0 ]
[root@jay-linux image]# vgchange -ay VolGroup
2 logical volume(s) in volume group "VolGroup" now active
[root@jay-linux image]# lvs
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert
lv_root VolGroup -wi-a--- 45.57g
lv_swap VolGroup -wi-a--- 3.94g
[root@jay-linux image]# mount /dev/VolGroup/lv_root /media/
[root@jay-linux image]# ls /media/
bin cgroup etc lib lost+found misc net proc sbin srv tmp var
boot dev home lib64 media mnt opt root selinux sys usr

（使用完后的卸载操作，如下）
[root@jay-linux image]# umount /media/
[root@jay-linux image]# vgchange -an VolGroup
0 logical volume(s) in volume group "VolGroup" now active
[root@jay-linux image]# losetup -d /dev/loop0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

[root@jay-linux image]# fdisk -lu rhel6u2.img You must set cylinders. You can do this from the extra functions menu. Disk rhel6u2.img: 0 MB, 0 bytes 255 heads, 63 sectors/track, 0 cylinders, total 0 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00048b34 Device Boot Start End Blocks Id System rhel6u2.img1 * 2048 1026047 512000 83 Linux Partition 1 does not end on cylinder boundary. rhel6u2.img2 1026048 104857599 51915776 8e Linux LVM Partition 2 has different physical/logical endings: phys=(1023, 254, 63) logical=(6527, 21, 22) [root@jay-linux image]# echo $((1026048*512)) 525336576 [root@jay-linux image]# losetup /dev/loop0 rhel6u2.img -o 525336576 [root@jay-linux image]# pvscan PV /dev/loop0 VG VolGroup lvm2 [49.51 GiB / 0 free] Total: 1 [49.51 GiB] / in use: 1 [49.51 GiB] / in no VG: 0 [0 ] [root@jay-linux image]# vgchange -ay VolGroup 2 logical volume(s) in volume group "VolGroup" now active [root@jay-linux image]# lvs LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert lv_root VolGroup -wi-a--- 45.57g lv_swap VolGroup -wi-a--- 3.94g [root@jay-linux image]# mount /dev/VolGroup/lv_root /media/ [root@jay-linux image]# ls /media/ bin cgroup etc lib lost+found misc net proc sbin srv tmp var boot dev home lib64 media mnt opt root selinux sys usr （使用完后的卸载操作，如下） [root@jay-linux image]# umount /media/ [root@jay-linux image]# vgchange -an VolGroup 0 logical volume(s) in volume group "VolGroup" now active [root@jay-linux image]# losetup -d /dev/loop0

mount LVM 分区的 参考资料：

Related posts:

如何挂载qcow2格式的镜像文件（how to mount a qcow2 image)

Linux挂载NTFS分区：mount unknown filesystem type ‘ntfs’

Ubuntu上的android sdk: ./emulator: No such file or directory

“mount: could not find any free loop device”解决方案