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170 lines
4 KiB
Text
170 lines
4 KiB
Text
[[ch-build-custom-kernel]]
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= Building a Custom Kernel
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[NOTE]
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====
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This document provides instructions for advanced users who want to rebuild the kernel from source.
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Any issues with a custom kernel build are *not supported* by the Fedora kernel team.
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====
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[[sect-why-build-a-custom-kernel]]
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== Why Build a Custom Kernel?
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Some common reasons to build a custom kernel are to:
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.. Change configuration options
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.. Troubleshoot issues
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.. Add patches
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[[sect-preparing-to-build-a-custom-kernel]]
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== Preparing to build a custom kernel
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The Fedora kernel is just another package in Fedora and can be compiled like any other application.
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The easiest way to compile the kernel is to use the tools provided by the `fedora-packager` package.
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This will install basic tools like `fedpkg` which is used to download the kernel source code onto your computer.
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To install `fedora-packager` from the command-line, enter:
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[source,bash]
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----
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sudo dnf install fedora-packager
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----
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`fedpkg` will make a clone of the Fedora kernel from link:++http://pkgs.fedoraproject.org/cgit/rpms/kernel.git/++[pkg-git] into a directory called ‘kernel’.
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By default, the source that is "checked out" will be the link:++https://fedoraproject.org/wiki/Releases/Rawhide++[Rawhide] kernel.
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Each Fedora release has its own branch and you can change branches using `git` commands.
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For example, to "check out" the source for Fedora 27, we would run the following commands:
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[source,bash]
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----
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fedpkg co -a kernel
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cd kernel
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git checkout -b my_kernel origin/f27
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----
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This creates a git branch named 'my_kernel' containing the kernel source for Fedora 27.
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[NOTE]
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====
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Be sure to change the version number to whatever version of Fedora you are using.
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====
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[[sect-building-the-kernel]]
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== Building the kernel
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The kernel has a number of build dependencies that can be installed with:
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[source,bash]
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----
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sudo dnf builddep kernel.spec
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----
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Changes to kernel configuration options can be added to the file `config-local`.
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When building a kernel for testing, it is best to use an identifiable name.
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This makes it easy to distinguish your custom kernel from the official Fedora kernel builds.
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Find the line in the `kernel.spec` file that says:
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`# define buildid .local`
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and change it to:
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`%define buildid .my_kernel`
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This will add _my_kernel_ to the the RPM package file names and will look something like this:
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`kernel-4.15.3-300.my_kernel.fc27.src.rpm`
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To build the packages enter:
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[source,bash]
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----
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fedpkg local
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----
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This will create all the kernel packages in the `x86_64` directory (or the name of the architecture you are building for).
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This will take a long time as it is creating all the kernel, module and debug packages.
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Also, it will require over 12 GB of disk space.
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If you want to create only the kernel and modules packages, you can use the `fast-build.sh` script.
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First enter:
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[source,bash]
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----
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fedpkg srpm
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----
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The result should look something like this:
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`Wrote /current/path/kernel-4.15.3-300.my_kernel.fc27.src.rpm`
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Now enter:
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[source,bash]
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----
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./scripts/fast-build.sh x86_64 kernel-4.15.3-300.my_kernel.fc27.src.rpm
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----
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If you need to add patches use the script `newpatch.sh` like this:
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[source,bash]
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----
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./scripts/newpatch.sh my-patch.patch
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----
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(where `my-patch.patch` is the file name of the patch.)
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Once it is complete, you can install/update your system with your custom kernel build.
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`cd` into the directory created in the kernel build process (`x86_64`, `x86`, etc.) and type:
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[source,bash]
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----
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sudo dnf update kernel*.rpm
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----
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It will update any kernel packages you currently have installed on your computer.
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[[sect-additional-resources]]
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== Additional Resources:
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For more information on building a custom kernel refer to the link:++https://fedoraproject.org/wiki/Building_a_custom_kernel++[Fedora Wiki: Building a Custom Kernel].
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[[sect-credit]]
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== Credits:
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This document is an updated and edited version of the article link:++https://fedoramagazine.org/building-fedora-kernel/++[Building the Fedora Kernel] from the link:++https://fedoramagazine.org++[Fedora Magazine].
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