Kernel versions supported by different RHEL versions

[achak01]

Can anyone pls tell me is there any link between the kernel versions and RHEL versions. Means what is the limits on the kernel version we can install on a particular RHEL version

[Matti_Kurkela]

Welcome to the ITRC Forums!

As far as I've understood, the supported kernel version for any particular major release of RHEL is chosen at some point before official release. Bug fixes and update releases ("Update N" or 5.1, 5.2, 5.3...) won't change this kernel version: any new features are back-ported to the release kernel version.

The officially supported kernel versions:
RHEL 3 - 2.4.21.
RHEL 4 - 2.6.9.
RHEL 5 - 2.6.18.

For example, a kernel package for RHEL 5 might be named as "kernel-2.6.18-XX.YY.ZZ.rpm". According to RedHat's policy, the 2.6.18 part will stay the same during the entire lifetime of the RHEL 5. Any bug-fixes and backported features are delivered as new XX.YY.ZZ versions.

If you use a kernel that is not packaged by RedHat, you are using a custom system. I don't think RedHat guarantees anything in such a case, but they may provide best-effort support if they so choose.

If you are asking "what can I technically do if I ignore the support question", then you should read the "linux-x.y.zz/Documentation/Changes" file included in every modern Linux kernel source package. The second chapter in the file is "Current Minimal Requirements" and it lists the software components that communicate directly with the kernel. It even lists the commands you'll need to verify the version numbers.

If your RHEL version can meet or exceed these minimum version requirements, you should be technically able to use that kernel with RHEL.

But if you are using a custom kernel, why are you paying for RHEL at all, instead of using the free CentOS Linux (compiled from the exact same source code as the corresponding RHEL)?

MK