Kernel Upgrade process

1)To check which kernels are installed, run the following command:

$ rpm -qa grep kernel

2)To check which kernel is currently running, execute the following command:

$ uname -r

3)For example, to install the 2.4.21-32.0.1.ELhugemem kernel, download the kernel-hugemem RPM and execute the following command:

# rpm -ivh kernel-hugemem-2.4.21-32.0.1.EL.i686.rpm

4) Never upgrade the kernel using the RPM option '-U'.

The previous kernel should always be available if the newer kernel does not boot or work properly.

5)To make sure the right kernel is booted, check the /etc/grub.conf file if you use GRUB and change the "default" attribute if necessary.

Here is an example:

default=0
timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title Red Hat Enterprise Linux AS (2.4.21-32.0.1.ELhugemem)

root (hd0,0)
kernel /vmlinuz-2.4.21-32.0.1.ELhugemem ro root=/dev/sda2
initrd /initrd-2.4.21-32.0.1.ELhugemem.img
title Red Hat Enterprise Linux AS (2.4.21-32.0.1.ELsmp)

root (hd0,0)
kernel /vmlinuz-2.4.21-32.0.1.ELsmp ro root=/dev/sda2
initrd /initrd-2.4.21-32.0.1.ELsmp.img

In this example, the "default" attribute is set to "0" which means that the 2.4.21-32.0.1.ELhugemem kernel will be booted.

If the "default" attribute would be set to "1", then 2.4.21-32.0.1.ELsmp would be booted.

6)After you installed the newer kernel reboot the system.

7)Once you are sure that you don't need the old kernel anymore, you can remove the old kernel by running:

# rpm -e

When you remove a kernel, you don't need to update /etc/grub.conf.