hi all, I use RHEL3U3, and I want to upgrade the kernel from 2.4.21-20 to 2.4.25.
I downloaded the kernel from kernel.org, but after I compiled and installed it, it can't startup with the new kernel.
my question is:

1. must I get kernel from Redhat?
2. what is the right way to upgrade my kernel?

thanks.

There are a variety of reasons why your new kernel will not boot. One of these is that you may not have told your boot loader about the new kernel. The kernel image should be in the /boot directory, & the boot loader config file (which will be in /etc) needs to have an entry for that kernel image. I don't know whether RHEL3U3 uses lilo or grub as the boot loader. In the case of lilo you not only have to alter the configuration file, but also you have to run lilo _before_ restarting the machine. When you run lilo it reports back about what kernel images it has found and whether they seem acceptable. In the case of grub this is not necessary, you only have to alter the config file and then restart.

A word of advice - always back up the config file before making alterations.

The other problem is that if you have compiled the kernel from source (which I understand you have done) you may not have got the right kernel configuration settings. An example of a particularly silly mismatch would be to configure for a pentium 4 when you are using an athlon processor. Your kernel needs a decent set of configuration options, matched to the PC hardware, to get a successful boot.

If you can find the configurations settings for the previous kernel then it is usually possible to build the kernel against the old configuration file using something like make oldconfig. You have to provide for missing configuration options, but at least that will make the majority of them match the hardware, which may in turn be sufficient to boot successfully so that you can move on to fine tuning of the kernel afterwards.

Normally the documentation that comes with the kernel is pretty clear about how to do an install. If you are having boot problems you should read it carefully, because its likely that there will be suggestions there about overcoming the particular problems that you are experiencing.

Incidentally once you have upgraded your kernel 2.4 you might consider the 2.6 series, which could run on your machine quite happily. I have an old redhat setup (7.3, I think) running with kernel 2.6.11, and a variety of modifications.

One other thing to be careful about is not to modify your kernel header files. The kernel header files should always correspond with the version of glibc that you are running. In practice this typically means that you should not use the kernel header files that go with your kernel. You should use the kernel header files that go with your glibc. That sounds a bit odd but Linus has explained it elsewhere. In practice this doesn't mean that you have to do something special for building your new kernel. It will be fine as it comes. What it means is that you should not start to reconfigure your machine subsequently on the grounds that you are running a new kernel - that can be a mistake. Any new packages need to be built using the same kernel headers that your glibc was built against.

thanks for kindly help.
so I will try to make oldconfig first, and then make new kernel with the structions in the new version release.
I will try it again.

Be careful to try with kernel 2.4 first before looking at 2.6. Once you have got used to the basics of kernel upgrading you can look at 2.6 with realistic hopes for success. Installing 2.6 needs a few utility upgrades and installs to work properly.

By the way, even for 2.4 you may need to upgrade your modutils. You should check in the kernel documentation about that. The point is that your kernel may need to install modules at runtime, in which case it needs certain utilities to manage the loading of those modules.

There are some articles on line about kernel upgrades.