HELP: FC6 kernel on CentOS 4.4 breaks things

[me at mattgillen.net (Matthew Gillen)]

Kristian Hermansen wrote:
> I have been desperately awaiting the official release of RHEL5 so that
> CentOS-5 can be released and utilized.  So far, it has been delayed
> almost a week now.  I am attempting to create a semi-supported server
> with a 2.6.18 kernel, which has the new libata subsystem (since
> 2.6.15) and native command queueing (NCQ), but I get stuck at every
> juncture.  I'm looking for suggestions on where I might go from here.
> Following are relevant fact and details for the ongoing problem.
> 
> * RHEL4 (CentOS 4.4) is supported by VMware Server 1.0.2
> * VMware Server 1.0.2 is known to be semi-broken on kernels >= 2.6.19
> * SATA performance on 2.6.9 is horrendous, compared to kernel 2.6.17+
>  * Thus, we need at least this kernel level.
>  * 2.6.18 adds NCQ, so we want that
> * Building a Vanilla kernel is not useful, since all the distro
> patches for CentOS will be unapplied, and applying all of them myself
> is asking for trouble according to the devs @ #centos
> * Using the Fedora Core 6 kernel with PAE extensions for > 4GB
> (kernel-PAE-2.6.18-1.2798.fc6) on CentOS 4.4 with --nodeps works for
> the most part, but breaks hal/hotplug
> * Trying to reconfigure VMware Server insitially resulted in a warning
> that gcc3 (CentOS) should not be used to compile modules for my kernel
> that built with gcc4 (FC6).  So, I installed gcc4 from source, since
> gcc4.1.1 package requires libc upgrade and I don't want to do that!
> <snip>

If you *really* want to burn some time with something that may not work,
then here's my suggestion:
  Grab the kernel-source packages for both the CentOS kernel and the FC6
kernel.  (you'll be using CentOS's native version to build the kernel, so if
you don't want to pollute your system you can get rid of gcc4)
  Follow the directions in section 8.6 of Fedora's release notes on how to
build a custom kernel (
http://fedora.redhat.com/docs/release-notes/fc6/en_US/sn-Kernel.html ),
except that the kernel .config you'll be using will the the one swiped from
the CentOS kernel-sources.
  Go through the steps and do the 'make oldconfig'

  Then finish the build of the FC6 kernel sources:
 rpmbuild --short-circuit -bc --target $(uname -m) kernel-2.6.spec
or something like that (I haven't built rpms from source with custom changes
to the source in a while, so I can't remember the exact next steps, but you
might need to repeat the last command and replace the '-bc' with '-bi' as
well...).  Eventually you'll get an RPM for your new FC6-based kernel.

If you really want to do some things that are highly not recommended by
anyone, and might melt your monitor or over-heat your hard-drive (which, by
the way, I would bear no responsibility for): when you install the source
rpms of the kernel source, you can compare patches of the different kernels
and see if there are any in the CentOS one that look like they might be
needed (the SOURCES directory of your rpmbuild environment contains both the
upstream pristine source .tar.gz, and all the distro-specific patches, and
the 'prep' stage of the rpmbuild command applies those patches after
untarring the source into the BUILD directory).

That should keep you busy for a while ;-)
HTH,
Matt

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