Changing kernel in grub 2

[Joe Zeff]

On 02/03/2012 11:19 AM, don fisher wrote:
>
> If the current kernel does not work as desired, how does one choose the
> previous kernel? The only choices I see are:
>
> 1. edit the script that says do not edit
> 2. remove the bad kernel from /boot and run grub2-mkconfig
>
> Please advise. Once boot is broken, it is really bad!

Currently, I have to select an old 2.x kernel on my laptop because all 
of the 3.x kernels hang.  It's safe to edit /boot/grub2/grub.cfg if 
you're careful, but the next time it's generated your changes will go 
away.  One thing that's safe to change is the timeout period, because 
all that does is decide how long you have before grub2 starts booting 
your default kernel.  Setting it to 5 gives you five seconds, and that 
should be ample because once you press the ANY key, the timer stops; if 
you have good reflexes, or quick boot times are important, three's 
probably ample.