RHEL5 Kernel HOWTO

1. Downgrade udev to a version compatible with kernels previous than 2.6.27:

echo ">=sys-fs/udev-147" >> /etc/portage/package.mask
emerge -u udev

2. Mask any openvz-sources version equal or newer than 2.6.27:

echo ">=sys-kernel/openvz-sources-2.6.27" >> /etc/portage/package.mask

3. openvz-sources-2.6.18* needs gcc-4.1*, so you must install it prior build your future downgraded kernel. If you have newer versions than gcc-4.1* then you must install this one. Also check your CFLAGS if you are using gcc-4.3* or later *AND* your make.conf CFLAGS has -march=native, due previous GCC versions doesn't allow it. Check [1] and put a correct -march directive in your CFLAGS. You also need to change CXXFLAGS in the same way, ie:

CFLAGS="-march=amd64" CXXFLAGS="-march=amd64" emerge =sys-devel/gcc-4.1.2

That may take a while, take a cup of your favourite beverage and wait until finish.

[1] http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/i386-and-x86_002d64-Options.html#i386-and-x86_002d64-Options

4. Switch to gcc-4.1* on your system:

localhost ~ # gcc-config -l
 [1] x86_64-pc-linux-gnu-4.1.2
 [2] x86_64-pc-linux-gnu-4.4.3 *
localhost ~ # gcc-config 1
* Switching native-compiler to x86_64-pc-linux-gnu-4.1.2...
>>> Regenerating /etc/ld.so.cache...                                                                                                                                                                                                     [ok]

* If you intend to use the gcc from the new profile in an already
* running shell, please remember to do:

*   # source /etc/profile

localhost ~ # source /etc/profile
localhost ~ # gcc --version
gcc (GCC) 4.1.2 (Gentoo 4.1.2 p1.3)
gcc (GCC) 4.1.2 (Gentoo 4.1.2 p1.3)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

localhost ~ #

5. Rebuild your sources:

cd /usr/src/linux
make menuconfig
[do your work]
make
cp arch/x86/boot/bzImage /boot/linux-2.6.18-openvz-028.068.9

6. Update /etc/boot.conf to point to your new kernel, ie:

vi /etc/boot.conf
[inside /etc/boot.conf now]
"Funtoo Linux" {
        kernel linux-2.6.18-openvz-028.068.9
        params root=/dev/sda3
}

7. Reboot your computer and enjoy

reboot