View source for User:Anthumchris:How to build the Alpine Linux kernel

== How to build the Alpine Linux kernel ==
This [[Tutorials and Howtos|Howto]] quickly demonstrates building/compiling the default Alpine Linux [[Kernels|kernels]]. Kernel customizations (not covered here) allow you to experiment by adding/removing kernel modules/features. For example, Alpine releases multiple [[Kernels|kernels]] that vary in features and file sizes.  Alpine kernels extend the standard [https://www.kernel.org/linux.html Linux kernel] and build within a few minutes to a few hours (depending on the speed of your system) using <code>[[abuild]]</code>, [https://gitlab.alpinelinux.org/alpine/aports aports], and [https://pkgs.alpinelinux.org/package/edge/main/x86_64/alpine-sdk alpine-sdk].

== Before you start ==
A running instance of Alpine Linux and a non-root user with [https://pkgs.alpinelinux.org/package/edge/main/x86_64/doas doas] privileges (i.e. sudo, wheel group) are required to use <code>[[abuild]]</code>.

== Build & install the kernel ==

=== Build ===
<pre>
doas apk add alpine-sdk
doas addgroup USERNAME abuild         # your non-root user

git clone --depth 1 https://gitlab.alpinelinux.org/alpine/aports.git
abuild-keygen --append --install
doas chmod a+r /etc/apk/keys/*        # ensure new keys are readable

cd aports/main/linux-lts/
time abuild -crK
</pre>

=== Identify backup ===

Identify the package name of your current kernel (e.g. linux-lts, linux-virt). This example shows that '''linux-lts''' is the current package that we would revert to as a backup.

<pre>
echo "kernel: $(uname -r)"
apk list --installed linux-*
</pre>

[[File:Alpine-kernel-package2.png|600px]]

=== Install ===
Find the newly-built kernel file to install. This example shows how to install a newly-built x86_64 LTS kernel:

<pre>
ls -r ~/packages/main/*
doas apk add FILENAME
doas reboot
</pre>

[[File:Alpine-kernel-install.png|600px]]

After rebooting, verify the newly-installed kernel version:
<pre>
echo "kernel: $(uname -r)"
</pre>

[[File:Alpine-kernel-new.png|320px]]

=== Revert ===
If needed, revert to the previous backup kernel package we identified earlier. This example shows how to revert to the previous "alpine-lts" package after removing the newly-installed "alpine-lts" (both are named "alpine-lts" yet refer to different versions/locations):
<pre>
apk list linux-lts            # newly-compiled kernel installed
doas apk del linux-lts        # newly-compiled kernel from file
doas apk add linux-lts        # previous kernel from Alpine repo
apk list linux-lts            # previous kernel installed
doas reboot
</pre>

[[File:Alpine-kernel-revert.png|465px]]

== See Also ==

* [[Kernels]]
* [[Custom Kernel|Custom Kernel (2018-present)]]