Merge #985

985: Permit raspberry pi (and other architectures) builds r=mergify[bot] a=abondis

## What type of PR?

Enhancement

## What does this PR do?

Add an option to select base images and permit building for different CPU architectures.

### Related issue(s)
N/A

## Prerequistes

- [X] documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.


Co-authored-by: Aurélien Bondis <aurelien.bondis@gmail.com>
Co-authored-by: Aurelien <aurelien.bondis@gmail.com>

docs/Dockerfile

@@ -1,12 +1,13 @@
-FROM python:3-alpine
+ARG DISTRO=alpine:3.8
+FROM $DISTRO
 
 COPY requirements.txt /requirements.txt
 
 ARG version=master
 ENV VERSION=$version
 
-RUN pip install -r /requirements.txt \
- && apk add --no-cache nginx curl \
+RUN apk add --no-cache nginx curl python3 \
+ && pip3 install -r /requirements.txt \
  && mkdir /run/nginx
 
 COPY ./nginx.conf /etc/nginx/conf.d/default.conf

docs/rpi_build.rst

@@ -0,0 +1,25 @@
+.. _rpi_build:
+
+Building for a Raspberry Pi
+===========================
+
+The build does not need to be done on the Pi.
+
+To do so, go to ``tests/`` and call ``./build_arm.sh``, it will build all
+necessary images for arm.
+
+To push the locally built images to a remote server, run ``./deploy_to_pi.sh``.
+Docker 18.09+ is needed to use ``-H ssh://<user>@<host>``.
+
+Adjustments
+-----------
+
+``build_arm.sh`` uses some variables passed as ``build-arg`` to docker-compose:
+
+- ``ALPINE_VER``: version of ALPINE to use
+- ``DISTRO``: is the main distro used. Dockerfiles are set on Alpine 3.10, and
+  build script overrides for ``balenalib/rpi-alpine:3.10``
+- ``QEMU``: Used by webmails dockerfiles. It will add ``qemu-arm-static`` only
+  if ``QEMU`` is set to ``arm``
+- ``ARCH``: Architecture to use for ``admin``, and ``webmails`` as their images
+  are available for those architectures.

docs/setup.rst

@@ -19,9 +19,7 @@ Prepare the environment
 
 Mailu images are designed to work on x86 or equivalent hardware, so it
 should run on pretty much any cloud server as long as enough power is
-provided. If you find yourself running Mailu on small hardware, e.g.
-Raspberry Pi or other platforms based on ARM, you will probably find
-some support from `MFAshby's fork`_.
+provided. For non x86 machines, see :ref:`rpi_build`
 
 You are free to choose any operating system that runs Docker (>= 1.11),
 then chose between various flavors including Docker Compose, Kubernetes
@@ -34,7 +32,6 @@ You should also have at least a DNS hostname and a DNS name for receiving
 emails. Some instructions are provided on the matter in the article
 :ref:`dns_setup`.
 
-.. _`MFAshby's fork`: https://github.com/MFAshby/Mailu
 
 Pick a Mailu version
 --------------------