How to build the Alpine Linux kernel

This Howto quickly demonstrates building/compiling the default Alpine Linux kernels "LTS" and "virt". Alpine kernels extend the standard Linux kernel and build within a few minutes to a few hours (depending on the speed of your system) using abuild, aports, and alpine-sdk.

Kernel customizations (not covered here) allow you to experiment by adding/removing kernel modules/features. Alpine releases multiple downloads which contain kernels that vary in features and file sizes.

Before you start

A running instance of Alpine Linux and a non-root user with doas privileges (i.e. sudo, wheel group) are required to use abuild.

Build & install the kernel

Build

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

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.

echo "kernel: $(uname -r)"
apk list --installed linux-*

Install

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

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

After rebooting, verify the newly-installed kernel version:

echo "kernel: $(uname -r)"

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):

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