7.5.4. Upgrading your kernel

Most Linux installations are fine if you periodically upgrade your distribution. The upgrade procedure will install a new kernel when needed and make all necessary changes to your system. You should only compile or install a new kernel manually if you need kernel features that are not supported by the default kernel included in your Linux distribution.

Whether compiling your own optimized kernel or using a pre-compiled kernel package, install it in co-existence with the old kernel until you are sure that everything works according to plan.

Then create a dual boot system that will allow you to choose which kernel to boot by updating your boot loader configuration file grub.conf. This is a simple example:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making config changes. 
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, e.g.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/hde8
#          initrd /initrd-version.img
#boot=/dev/hde
default=0
timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title Red Hat Linux new (2.4.9-31)
        root (hd0,0)
        kernel /vmlinuz-2.4.9-31 ro root=/dev/hde8
        initrd /initrd-2.4.9-31.img
title old-kernel
        root (hd0,0)
        kernel /vmlinuz-2.4.9-21 ro root=/dev/hde8
        initrd /initrd-2.4.9-21.img

After the new kernel has proven to work, you may remove the lines for the old one from the GRUB config file, although it is best to wait a couple of days just to be sure.