we upgrade ubuntu kernal ,sometimes it may be not adapt to hardware.we can reboot into the start menu, select advance mode and enter into old kernal.But if the old kernal was broken or uninstalled. it has troubles to be resolved.
The First step.let the system enter from LiveCD.Copy two files from the original iso,which include named vmlinuz and initrd.lz in casper document.at last. we move the two file into /boot document and reboot.we press "e" to edit the gurb at the start menu.
Entry following text,Take care editing the pink colour word adapt your actual enviroment.
set root=(hd0,msdos9)
linux /boot/vmlinuz root=UUID=xxx ro locale=zh_CN quiet splash
initrd /boot/initrd.lz
boot
root=UUID=xxx，The xxx is your boot partion's ID，you can get it from input sudo blkid command.it's like a sting of efffc2c1-30ae-42c6-b287-ea297cc7b1c2
Now we have already enter into normal system.Then we need install a new kernal substitute for old one。In terminal.excute the following command
apt-cache search header #find the new kernal in result
apt-get install linux-headers-x.x.x-xx #install kernal
apt-get install linux-p_w_picpath-x.x.x-xx
