Linux Kernel Module Programming Guide

For full kernel recompilations (i.e. other options, add-on patches, non-modular code), the source RPM (SRPM) is required. Proceed as follows:

1. Set up your RPM environment to not compile as "root", see for example the RPM tutorial
2. install the source RPM of the kernel version you'd like to modify (take care not to pick an old-and-insecure version), e.g.

rpm -ivh http://linuxsoft.cern.ch/cern/slc4X/updates/SRPMS/kernel-2.6.9-34.0.2.EL.cern.src.rpm

This creates a .tar.gz and lots of patches under ..../SOURCES/ (wherever you have configured RPM, default would be /usr/src/redhat/SOURCES but you are not doing this as "root", right??)

1. run rpmbuild --target i686 -bp ..../SPECS/kernel-2.6-cern.spec (or similar) - this unpacks the .tar.gz and applies the patches, all under ..../BUILD/
2. modify the extracted version, twiddle and compile. Warning: re-running rpmbuild at this stage will happily overwrite any local modifications.
3. optional but really recommended: create a patch from your modifications, add it to ..../SOURCES, add it to the ..../SPEC/kernel-2.6-cern.spec file. And edit the .spec file to change the "Release" string, so that your modified kernel RPM can easily be identified. Then invoke rpmbuild --target i686 -bb ..../SPEC/kernel-2.6-cern.spec to get a nicely-packaged custom kernel RPM that is readily installable.

(substitute i686 in the above with x86_64 or ia64 as required). Please remember that you may have to redo standalone modules (such as OpenAFS) against your new kernel.