x86 Systems
All x86 systems (including all AMD64 systems) use GRUB as the boot loader.
Confirm that the file If a separate Notice that the default is not set to the new kernel. To configure GRUB to boot the new kernel by default, change the value of the Begin testing the new kernel by rebooting the computer and watching the messages to ensure that the hardware is detected properly.
GRUB
/boot/grub/grub.conf contains a title section with the same version as the kernel package just installed
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/hda2
# initrd /initrd-version.img
#boot=/dev/hda
default=1 timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title Community Enterprise Linux (2.6.9-5.EL)
root (hd0,0)
kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/
initrd /initrd-2.6.9-5.EL.img
title Community Enterprise Linux (2.6.9-1.906_EL)
root (hd0,0)
kernel /vmlinuz-2.6.9-1.906_EL ro root=LABEL=/
initrd /initrd-2.6.9-1.906_EL.img
/boot/ partition was created, the paths to the kernel and initrd image are relative to /boot/.
default variable to the title section number for the title section that contains the new kernel. The count starts with 0. For example, if the new kernel is the first title section, set default to 0.