[mc] Check writability of /data before chown'ing it

For #104

minecraft-server/Dockerfile

@@ -19,7 +19,8 @@ RUN useradd -s /bin/false --uid 1000 minecraft \
   && mkdir /config \
   && mkdir /mods \
   && mkdir /plugins \
-  && chown minecraft:minecraft /data /config /mods /plugins
+  && mkdir /home/minecraft \
+  && chown minecraft:minecraft /data /config /mods /plugins /home/minecraft
 
 EXPOSE 25565 25575
 

minecraft-server/start.sh

@@ -4,16 +4,17 @@ set -e
 usermod --uid $UID minecraft
 groupmod --gid $GID minecraft
 
-chown -R minecraft:minecraft /data /start-minecraft /home/minecraft
+fix_ownership() {
-chmod -R g+wX /data /start-minecraft
+  dir=$1
+  if ! sudo -u minecraft test -w $dir; then
+    echo "Correcting writability of $dir ..."
+    chown -R minecraft:minecraft $dir
+    chmod -R u+w $dir
+  fi
+}
 
-while lsof -- /start-minecraft; do
+fix_ownership /data
-  echo -n "."
+fix_ownership /home/minecraft
-  sleep 1
-done
-
-mkdir -p /home/minecraft
-chown minecraft: /home/minecraft
 
 echo "Switching to user 'minecraft'"
 exec sudo -E -u minecraft /start-minecraft "$@"