ARM support notes (#12)

* Add note about available packages for Debian on ARM.
* Mention multi-CPU architecture support for Docker.

source/docker.rst

@@ -17,11 +17,15 @@ platforms" documentation
 Fetching and Running Krill
 --------------------------
 
-The :command:`docker run` command will automatically fetch the Krill image the
-first time you use it, and so there is no installation step in the traditional
-sense. The :command:`docker run` command can take `many arguments
-<https://docs.docker.com/engine/reference/run/>`_ and can be a bit overwhelming
-at first.
+The :command:`docker run` command will automatically fetch the Krill image for
+your CPU architecture the first time you use it, and so there is no installation
+step in the traditional sense. The :command:`docker run` command can take `many
+arguments <https://docs.docker.com/engine/reference/run/>`_ and can be a bit
+overwhelming at first.
+
+.. Note:: The CPU architectures supported by the Krill Docker image are shown
+   on the `Docker Hub Krill page <https://hub.docker.com/r/nlnetlabs/krill/tags>`
+   per Krill version (aka Docker "tag") in the `OS/ARCH` column.
 
 The command below runs Krill in the background and shows how to configure a few
 extra things like log level and volume mounts (more on this below).

source/install-and-run.rst

@@ -30,7 +30,12 @@ public rsyncd and HTTPS web server available.
 
        If you have a machine with an amd64/x86_64 architecture running Debian 9,
        10 or 11, you can install Krill from our `software package
-       repository <https://packages.nlnetlabs.nl>`_. 
+       repository <https://packages.nlnetlabs.nl>`_.
+
+       If your machine uses an ARM architecture we also provide (via the same
+       repository) ARMv6 & ARM64 packages for Debian 10 and an ARMv7 package for
+       Debian 11, intended to support Raspberry Pi 1b, Rock64 and Raspberry Pi 4b
+       respectively.
 
        First update the ``apt`` package index: