alpine-lima: build Alpine based ISO images for lima

Lima launches Linux Virtual Machines on macOS.

This repo contains the scripts and tools to build an ISO image for Lima to be used by Rancher Desktop.

The requirements include:

• Create the smallest image possible because it will be included in the download of the Rancher Desktop application.

• Don't bundle any software that will not be used by Rancher Desktop: beyond keeping the image small, it also avoids having to update the image when one of the packages that isn't even being used has a CVE issued against it.

• Include all the optional packages needed by Lima and Rancher Desktop, so no internet connection is required to start up Rancher Desktop.

Editions

The scripts in this repo can build multiple "editions" of the ISO: "min", "ci", "std", "k3s".

Minimum: min

The "min" edition is just the base image used for everything else. It does configure the network adapters but is otherwise identical to the Alpine "virt" flavour. It can be tested locally with qemu and a console window, but doesn't work with Lima because it doesn't include any cloud-init functionality.

Cloud-Init: ci

The "ci" edition just adds cloud-init on top of "min". It is used for testing Lima support for Alpine, to make sure that all optional packages are installed and configured correctly by the boot scripts.

Standard: std

The "std" edition uses a custom "lima-init" script instead of "cloud-init" to avoid pulling in all the additional dependencies. It includes all optional requirements from Lima.

Right now the "std" edition also installs qemu-aarch64 and configures it via binfmt_misc to be able to run Apple Silicon binaries. This is not the whole qemu-openrc package, but just the minimal subset for this one architecture, plus the configuration script.

Kubernetes: k3s

The "k3s" edition is the same as "ci" plus k3s pre-installed. This is still subject to change.

Architecture

This repo supports the generation of images for different architectures. Only x86_64 and aarch64 have been tested but other architectures can also be generated.

Building and testing

Note that this repo includes the Alpine aports repository as a submodule. If you didn't specify the --recursive option when cloning this repo, then you need to initialize the submodule by running:

git submodule update --init

The examples show the default values for ALPINE_VERSION=3.20.3 EDITION=std, ARCH defaults to the OS architecture uname -m. The options need to be specified only to select non-default setting.

Build the builder

The ISO builder will be created inside a docker image. You can specify the Alpine version used to create it:

make mkimage ALPINE_VERSION=3.20.3

Build the ISO

This docker image can then be used to create ISO images that will be stored under ./iso:

make iso ALPINE_VERSION=3.20.3 EDITION=std

Run the ISO with qemu

make run ALPINE_VERSION=3.20.3 EDITION=std

Run the ISO with Lima

make lima ALPINE_VERSION=3.20.3 EDITION=std