Simply move in to the boot/grub directory:

cd /boot/grub

You will find an archive called grub.conf , edit grub.conf with your favorite text editor:

vi grub.conf



As you can see on the image above, there is a setting that says "default=" , and below you will also see your 2 options of kernel, at least in the case above the single user processor kernel, and the smp capable kernel.

If you want your server or computer to boot into the smp capable (multi processor server) then change default to:

default=1

Or if you want the single processor kernel to boot as default, just change it to:

default=0

On your next reboot you will be able to see your changes.

As always ... I do hope this was useful
Felipe