CentOS cannot boot

I had couple of times with CentOS cannot boot.

Please read my previous article about how to use Ubuntu LiveCD, and mount CentOS Volume group disk. Then you can change the grub.cfg file.

http://fengweizhang.blogspot.com/2011/02/mount-lvm-partition-from-other-disk.html

But it didn't work for this time.

I cashed CentOS again by adding mem=2000 to the boot argument in grub.cfg. Even I used first method, it cannot find any file in /boot directory.

This time I soved by using CentOS LiveCD. It has an rescue function, and install grub and configure boot flag automatic.