How to upgrade kernel in RHEL, Suse, Ubuntu Linux

Step by step procedure to upgrade kernel in RHEL, Suse and Ubuntu Linux along with sample outputs of all the commands.

How to check current kernel & patch level in Linux

You can confirm current kernel version & patch level using uname -r and uname -v command.

-r switch gives you your current kernel version. -v gives you your current patch level. You can see in above output our RHEL6 system has 2014 (almost 4 years old) patched kernel. We will patch it to latest one in this article.

How to upgrade the kernel in RHEL

Patching kernel is Linux is same as upgrading to the latest kernel. Make sure you have yum configured properly to receive latest packages from trusted repositories. If you do not have/want yum configurations, you can download the latest kernel and its dependencies from Red Hat portal and keep it ready on the server for installation.

Never replace existing kernel by updating package. Always install new kernel package so that your old kernel still resides on server and you can boot it if your server/application is not behaving good with new kernel.

To install the latest kernel, use rpm -ivh <rpm names> or yum install kernel command.

If you are on test system and dont mind wiping out old kernel then you can directly use yum update kernel or rpm -Uvh <rpms> command and update kernel.

If you observe, yum resolved dependencies too. If you are opting to install from rpm you need to download all dependencies as well. Here is the list of dependencies depending on your RHEL version :

RHEL4 kernel package upgrade dependencies:kernel-smp, kernel-largesmp, kernel-hugemem
RHEL5 kernel package upgrade dependencies:kernel-PAE, kernel-xen
RHEL6 kernel package upgrade dependencies: kernel-firmware
RHEL7 kernel package upgrade dependencies:dracut, dracut-network, dracut-config-rescue

Now, if you observe,/boot/grub/grub.conf your newly installed kernel entry is added before your old kernel entry. This gives new kernel priority to boot when you reboot the system. parameter default=0 says the system needs to be booted from very first kernel defined below. Kernel entries numbering starts from 0. Make sure this parameter value points to your newly installed kernel and reboot the system.

After rebooting, you can see your system is running with new updated kernel!

You can see kernel is upgraded from 2.6.32-431.29.2.el6.x86_64 to 2.6.32-696.20.1.el6.x86_64. And patch level from July 2014 to Jan 2018.

How to upgrade the kernel in Suse Linux

Let’s start with checking current kernel version and patch info.

Perform kernel upgrade with zypper or if you have kernel rpm package with you, you can use rpm -ivh <kernel_rpm_path> to perform multi-kernel install (not update)

You have an option to perform distribution upgrade using zypper dup as well which includes updating all packages to available updates. But most of the cases its not recommended.

Reboot the system and then check new kernel version.

You can see kernel is upgraded from 3.0.101-108.21-default to 3.0.101-108.35-default. And patch date from Dec 2017 to Feb 2018!

How to upgrade the kernel in Ubuntu Linux

Start with checking your current kernel version and patching date

Now visit Ubuntu Kernel page and download kernel of your choice which is matching with your server arch using wget. We chose to upgrade to 4.10 kernel. Since we have generic kernel we downloaded generic kernel files from 4.10 directory.

Now install these kernel packages using dpkg command with -i switch.

After a successful install, reboot the system and check new kernel version.

You can see kernel is upgraded to 4.10.1-041001-generic from 4.9.0-15-generic. And patch date from Jan 2017 to Feb 2017.