currently have redhat 7.2 installed and lots of rpms.

When I install a new kernel, will I lose all my current rpms that are installed?
Will the rc.d directory stay the same or get overwritten?
What about drivers- At present the NIC types are automatically recognised - will this be the same after the new kernel is installed or do I have to do something extra to allow this detection process?

In short what data do I lose when I upgrade the kernel?

thanks

In general the kernel is *only* the core of the system. It is similar to the KERNEL32.DLL file on Win32 (to make a bit of an oversimplification).

The kernel is responsible for handling all devices. You will need to ensure that you have enabled support for your network card, sound card, etc., etc. or they will be unavailable with the new kernel.

Other than that though, nothing else will be affected. Your computer should start up the same, your GUI should be unaffected, your data files will be safe.

There are some caveats that you need to be aware of. These potential troubles exist in any operating system, not just Linux.

1- sometimes a new kernel will change an internal structure or otherwise break compatibility with existing tools. Linux is pretty decent about being careful about creating these structures in the first place so breaking compatibility (especially within a stable kernel progression) is very rare. Keep your old kernel around for a while just in case something breaks that you weren't expecting

2- Third-party modules (e.g. NVidia X drivers, HCF/HSF modem drivers, VMWare modules, etc.) will likely not work with a different kernel than what they were compiled with. Most times it's as simple as recompiling the driver but potential problem #1 lurks.

3- It's often best for new kernel upgraders to copy the new kernel to a floppy disk and boot off of that first to see if everything went well. It's no fun if you overwrite your original kernel and realize you for got something like a network driver or filesystem driver. Trust me. :-)

There is also a KERNEL-HOWTO available somewhere on the Linux Documentation Project (the LDP) -- it may be a good thing to look at.

--

These guidelines are for Linux in general. RedHat has, for whatever reasons, deviated from the standard kernel and has custom extensions to the standard kernel. All bets are off if you use a stock kernel with a RedHat system. If you stick to kernels (or patches) from RedHat, you shouldn't get into trouble. And if you stick with RPMs you should be pretty damn safe.

Here's a link I used for my first kernel recompiles:

http://www.linuxorbit.com/modules.ph...icle&artid=494

The only thing I'd add to the above post would be to keep your old kernel and just add the new one to your boot loader menu. That way, if there's a problem with the new one, you can boot to the old one and think things over.

For example, on my Slackware box, the default kernel is:

/boot/vmlinuz

When I compiled kernel 2.4.18, I named it:

/boot/linux-2.4.18

In /etc/lilo.conf, I copied the section for vmlinuz and changed the image and label entries to linux-2.4.18

Now, when I boot, I can choose either kernel to boot. That process may differ from your setup, but you may be able to do something similar.

j.

thanks guys