Kernel developers frequently request bug reporters test on a different kernel. Sometimes this is a full new version. Other times it’s a test build with a patch. This article shows you how to install a kernel someone has built elsewhere.
The kernel build process produces a long list of RPM packages. The most important ones are kernel, kernel-core, and kernel-modules:
- The kernel package doesn’t contain any files; its only purpose is to bring in the other two packages.
- kernel-core contains the files that end up in /boot and a set of kernel modules needed for core functionality.
- kernel-modules contains the rest of the modules that are installed with the system. (There is a kernel-modules-extra package as well which contains drivers for rare hardware.)
A developer who requests testing — such as for a bugfix or other change — typically gives a link to a koji build. Koji is the build system Fedora developers use to build software for inclusion into Fedora.
A build only for testing is called a scratch build. These scratch builds are only retained for a short time. After that, the Koji system collects them as garbage and gets rid of them. A scratch build isn’t signed, so to install it you need to turn off secure boot if it’s turned on. A koji build produces binaries for multiple architectures, as seen below.
A build of the Kernel in Koji
Get and install the kernel
Find the architecture you want to test (typically x86_64) and click the download link next to the kernel, kernel-core, and kernel-modules packages. Once the RPMs are downloaded, you can install them on the command line using dnf with sudo:
sudo dnf install ./path/to/kernel-4.10.8-100.fc24.x86_64.rpm ./path/to/kernel-core-4.10.8-100.fc24.x86_64.rpm ./path/to/kernel-modules-4.10.8-100.fc24.x86_64.rpm
You can then reboot into your new kernel. If you want to remove it after testing, make sure to remove all three packages kernel, kernel-core, and kernel-modules to fully remove the files.
James Hogarth
An easy way to grab all the packages is to do:
koji download-task –arch=x86_64
This grabs all the RPMs for that arch in the task to the current directory, so it’s worth doing it in a quick empty one.
Then you can install all the rpms you need. Don’t forget modules-extra if using something like an XBox controller with drivers in extras!
Paul W. Frields
@James: Correct. You can also do something like:
You need the koji package installed. For scratch builds this won’t work, though. There is a scratch build downloader in the fedora-review package, or download-task works fine as you mentioned. The instructions in the article will cover every case, though, even if they’re just a bit more manual.
Zach Villers
Great Article,
Are scratch-build kernels built for all releases or is that determined by the person submitting the build? Is it possible to mix a kernel built for F26 on an F25 system? (I know I can install any kernel on my system by building it, but are there packages on a F25 system that will update if I install a F26 kernel?
Jiri Kastner
i have kernel.repo with
##########
[kernel]
name=kernel
baseurl=file:///root/kernel
gpgcheck=0
metadata_expire=1s
#################
when downloaded from build to /root/kernel folder i just do createrepo_c /root/kernel && dnf update -c kernel.repo