Creating an Arch Linux (ARMv7) Docker Image

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Introduction

This post describes how to create a Docker image for a Raspberry Pi (2/3) based on Arch Linux (ARMv7hf). The example includes Mono but could be adapted as required.

Creating a Base Image

A base Arch Linux (Armv7hf) can be created from the following command. The command creates an untagged image from piped input and STDIN.

   curl -L http://archlinuxarm.org/os/ArchLinuxARM-rpi-2-latest.tar.gz | gunzip | sudo docker import -

The image should be visible using the following command

   docker images

This will return something along the lines of the following. The untagged image can be seen at the top of the list.

   REPOSITORY                  TAG                 IMAGE ID            CREATED             SIZE
   <none>                      <none>              ad615f58544f        1 minutes ago       686MB
   easypi/alpine-arm           <none>              fe637de3f099        4 months ago        5.78MB
   alexellis2/nginx-arm        <none>              f602e1a412d0        17 months ago       109MB

The image can then be tagged as appropriate e.g.

   docker tag ad615f58544f arch-armv7hf-base

This can then be used in a Docker file as shown below.

Building a Working Image

The Docker file used was as follows.

   FROM arch-armv7hf-base
   MAINTAINER John Newcombe
   ENV REFRESHED_AT 2017-10-28
   
   RUN pacman -Suy --noconfirm
   RUN pacman -S --noconfirm mono
   RUM mkdir /opt/gaf

Note: The command to create the folder /opt/gaf was added in this example as it will be used as a bind point later on.

Build the image with the command

   docker build --tag="johnnewcombe/arch-armv7hf" .

Testing the Image

Run the image with the following command

   docker run -it --name myContainer johnnewcombe/arch-armv7hf bash

This should give you a bash shell within the container. To check the version of mono the following command can be used

   mono -V

This should return something like the following

   Mono JIT compiler version 5.0.0 (Stable 5.0.0.100/9667aa6 Wed Jul 12 18:27:31 UTC 2017)
   Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
           TLS:           __thread
           SIGSEGV:       normal
           Notifications: epoll
           Architecture:  armel,vfp+hard
           Disabled:      none
           Misc:          softdebug 
           LLVM:          supported, not enabled.
           GC:            sgen (concurrent by default)


To push this up to the Docker Hub, use the following commands entering your password when requested.

   docker login --username=<USERNAME>
   docker push johnnewcombe/arch-armv7hf