RHEL 6: Compile stock-kernel

peter_b · Post by **peter_b** » Thu Feb 20, 2014 9:24 pm

NOTE: This is work in progress and not finished. Might even be complete nonsense, but I keep my notes here until I've completed this task.

I've compiled a kernel hundreds of times already in the past, but this time, it's not just the kernel, but building proper packages. It's a bit trickier.

I want to do it clean, and stick to the RHEL-way-of-doing-it as good as possible. Unfortunately, I couldn't find proper documentation about re-compiling the stock kernel (not plain-vanilla source) in any Redhat articles. I guess it's due to support reasons.

The information I found is for Fedora or CentOS, but seems to work fine.
Here are 2 good sources for getting started:

*) Install build-dependencies:
Some of the packages required for building the kernel are not in the default RHEL repositories. You must enable the "rhel-6-server-optional-beta-rpms" in "/etc/yum.repos.d/redhat.repo".

Search for a block like this:

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[rhel-6-server-optional-beta-rpms]
name = Red Hat Enterprise Linux 6 Server - Optional Beta (RPMs)
baseurl = https://cdn.redhat.com/content/beta/rhel/server/6/$releasever/$basearch/optional/os
enabled = 1
gpgcheck = 1
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-beta,file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
sslverify = 1
sslcacert = /etc/rhsm/ca/redhat-uep.pem
sslclientkey = /etc/pki/entitlement/4207967858922431493-key.pem
sslclientcert = /etc/pki/entitlement/4207967858922431493.pem
metadata_expire = 86400
ui_repoid_vars = releasever basearch

By default, it will have "enabled = 0". Change this to "enabled = 1".

Then run:

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$ sudo yum-builddep kernel

Which should find and install the required packages for building your kernel.

*) Prepare kernel build:
The build process generated gpg keys for signing kernel modules. Install "rng-tools", to feed the random number generator with enough entropy.
Then use "rngd" to feed /dev/urandom:

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$ sudo rngd -r /dev/urandom

If you don't do this, your rpmbuild will sit and wait for hours while generating the keys.

*) Rpmbuild kernel:
This builds only the base kernel (no xen, etc) without debuginfo:

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$ rpmbuild -bb --target=`uname -m` kernel.spec

You also have to compile again for "noarch", because otherwise you will run into the following dependency error when trying to install:

error: Failed dependencies:
kernel-firmware >= 2.6.32-431.5.1.el6.sil3826 is needed by kernel-2.6.32-431.5.1.el6.sil3826.x86_64

In order to avoid this, build "noarch" too, so the "kernel-firmware" package is also built:

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$ rpmbuild -bb --target=noarch kernel.spec

When the build process finished successfully, you will find the generated RPMs in "$HOME/rpmbuild/RPMS/", under their folders named after the built kernel package's architecture.

In my case (64bits), for example, the following files were created:
noarch:

.:
noarch
x86_64

./noarch:
kernel-abi-whitelists-2.6.32-431.5.1.el6.sil3826.noarch.rpm
kernel-doc-2.6.32-431.5.1.el6.sil3826.noarch.rpm
kernel-firmware-2.6.32-431.5.1.el6.sil3826.noarch.rpm

./x86_64:
kernel-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-debug-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-debug-debuginfo-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-debug-devel-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-debuginfo-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-devel-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
kernel-headers-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
perf-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
perf-debuginfo-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
python-perf-2.6.32-431.5.1.el6.sil3826.x86_64.rpm
python-perf-debuginfo-2.6.32-431.5.1.el6.sil3826.x86_64.rpm

*) Install the kernel:
Since the RPMs outside of a repository cannot install depending packages themselves, you must install the "kernel-firmware" manually before:

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$ sudo rpm -ivh $HOME/rpmbuild/RPMS/noarch/kernel-<version>.<arch>.rpm
$ sudo rpm -ivh $HOME/rpmbuild/RPMS/<arch>/kernel-<version>.<arch>.rpm

(Replace "<version>" with your kernel version name, and "<arch>" with your CPU architecture, such as "x86_64" for example)

In my case, the installation looked like this:

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[pb@bb2 RPMS]$ sudo rpm -ivh noarch/kernel-firmware-2.6.32-431.5.1.el6.sil3826.noarch.rpm 
Preparing...                ########################################### [100%]
   1:kernel-firmware        ########################################### [100%]
[pb@bb2 RPMS]$ sudo rpm -ivh x86_64/kernel-2.6.32-431.5.1.el6.sil3826.x86_64.rpm 
Preparing...                ########################################### [100%]
   1:kernel                 ########################################### [100%]

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