ARM SERVER 虚拟机挂载多块磁盘问题的解决方法

今天在ARM-SERVER上启动虚拟机发现总是mount不上根目录，报告错误为

Begin: Loading essential drivers ... done.

Begin: Running /scripts/init-premount ... done.

Begin: Mounting root file system ... Begin: Running /scripts/local-top ... done.

Begin: Loading essential drivers ... done.

Begin: Running /scripts/init-premount ... done.

Begin: Mounting root file system ... Begin: Running /scripts/local-top ... done.

Begin: Running /scripts/local-premount ... done.

mount: mounting /dev/vda on /root failed: Invalid argument

Begin: Running /scripts/local-bottom ... done.

done.

Begin: Running /scripts/init-bottom ... mount: mounting /dev on /root/dev failed: No such file or directory

done.

mount: mounting /sys on /root/sys failed: No such file or directory

mount: mounting /proc on /root/proc failed: No such file or directory

Target filesystem doesn't have requested /sbin/init.

No init found. Try passing init= bootarg.

虚拟机配置如下

....

    <disk type='file' device='disk'>

      <driver name='qemu' type='raw' cache='none'/>

      <source file='/home/liufeng/vm/disk/ubuntu-core-14.04.1-core-arm64.img'/>

      <target dev='vda' bus='virtio'/>

      <alias name='virtio-disk0'/>

      <address type='virtio-mmio'/>

    </disk>

    <disk type='file' device='disk'>

      <driver name='qemu' type='qcow2'  cache='none'/>

      <source file='/mnt/data.qcow2'/>

      <target dev='vdb' bus='virtio'/>

      <alias name='virtio-disk1'/>

      <address type='virtio-mmio'/>

    </disk>

....

其实是虚拟机的一个问题，将加入的空闲磁盘识别为vda了，本来应该将ubuntu-core-14.04.1-core-arm64.img识别为vda，结果被识别为vdb了（可以在(initramfs)下面mount /dev/vdb 看到）

解决问题思路如下

1. 找到vdb的UUID

(initramfs) blkid /dev/vdb

/dev/vdb: UUID="004802c8-b09c-4bf6-b2d9-6722bfcd851b" TYPE="ext4" 

2. 修改虚拟机启动参数，用UUID就和识别的盘符没有关系了，使用UUID永远是唯一的，vda也好，vdb也罢，都没有关系

  <os>

    <type arch='aarch64' machine='virt'>hvm</type>

    <kernel>/home/liufeng/vm/disk/vmlinuz-3.13.0-57-generic</kernel>

    <initrd>/home/liufeng/vm/disk/initrd.img-3.13.0-57-generic</initrd>

    <cmdline>console=ttyAMA0 root=UUID=004802c8-b09c-4bf6-b2d9-6722bfcd851b</cmdline>

    <boot dev='hd'/>

  </os>

3. 启动虚拟机，OK，注意这里新的磁盘变成了/dev/vda,后面别mount错了

虚拟机里面执行：

root@localhost:~# mkfs.ext2 /dev/vda

root@localhost:~# mount /dev/vda /mnt/