We need to set up the volume when the container runs, not when it is built, because mounting a volume over /var/lib/mediawiki will shadow the contents of that directory in the image.

Dockerfile

@@ -5,17 +5,18 @@
 FROM tutum/apache-php:latest
 MAINTAINER John E Arnold <iohannes.eduardus.arnold@gmail.com>
 
+WORKDIR /
+
 # Remove the old hello world app and grab Mediawiki source
+RUN apt-get update && apt-get install -yq git && rm -rf /var/lib/apt/lists/*
 RUN rm -fr /app && git clone https://gerrit.wikimedia.org/r/p/mediawiki/core.git /app
 RUN cd /app && git checkout -b REL1_23 origin/REL1_23
 
 # Create the section for persistent files
 RUN mkdir /var/lib/mediawiki
 
-# Move the files that need to be persistent and create symbolic links to them
+ADD setup.sh /setup.sh
-RUN mv /app/images /var/lib/mediawiki/ && ln -s /var/lib/mediawiki/images /app/images
+RUN chmod +x setup.sh
-RUN mv /app/skins /var/lib/mediawiki/ && ln -s /var/lib/mediawiki/skins /app/skins
-RUN touch /var/lib/mediawiki/LocalSettings.php && ln -s /var/lib/mediawiki/LocalSettings.php /app/LocalSettings.php
 
 EXPOSE 80
-CMD ["/run.sh"]
+CMD ./setup.sh && ./run.sh

setup.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+if [[ ! -d /var/lib/mediawiki/skins ]]; then
+    mv /app/images /var/lib/mediawiki/ && ln -s /var/lib/mediawiki/images /app/images
+    mv /app/skins /var/lib/mediawiki/ && ln -s /var/lib/mediawiki/skins /app/skins
+fi