用xen-create-image创建映像和cfg文件后，用xm create -c vm.cfg启动虚拟机实例，过程中找不到root fs，报错如下：
Gave up waiting for root device. Common problems:
- Boot args (cat /proc/cmdline)
- Check rootdelay= (did the system wait long enough?)
- Check root= (did the system wait for the right device?)
- Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/xvda2 does not exist. Dropping to a shell!
BusyBox v1.17.1 (Debian 1:1.17.1-8) built-in shell (ash)
Enter 'help' for a list of built-in commands.
/bin/sh: can't access tty; job control turned off
(initramfs)
主要原因在于所使用的内核缺block device driver，所以要安装带有block device driver的内核，解决方法如下：
1.# apt-get install -y linux-image-3.0.0-12-virtual
2.# vi /etc/xen/vm.cfg
=======================vm.cfg========================
[...]
kernel = '/boot/vmlinuz-3.0.0-13-virtual'
ramdisk = '/boot/initrd.img-3.0.0-13-virtual'
[...]
3.问题解决
