[minecraft] Pass GID as docker option

minecraft-server/Dockerfile

@@ -34,7 +34,7 @@ CMD [ "/start" ]
 # Special marker ENV used by MCCY management tool
 ENV MC_IMAGE=YES
 
-ENV UID=1000
+ENV UID=1000 GID=1000
 ENV MOTD A Minecraft Server Powered by Docker
 ENV JVM_OPTS -Xmx1024M -Xms1024M
 ENV TYPE=VANILLA VERSION=LATEST FORGEVERSION=RECOMMENDED LEVEL=world PVP=true DIFFICULTY=easy \

minecraft-server/README.md

@@ -68,15 +68,16 @@ to map a directory on your host machine to the container's `/data` directory, su
 When attached in this way you can stop the server, edit the configuration under your attached `/path/on/host`
 and start the server again with `docker start CONTAINERID` to pick up the new configuration.
 
-**NOTE**: By default, the files in the attached directory will be owned by the host user with UID of 1000.
-You can use an different UID by passing the option:
+**NOTE**: By default, the files in the attached directory will be owned by the host user with UID of 1000 and host group with GID of 1000.
+You can use an different UID and GID by passing the options:
 
-    -e UID=1000
+    -e UID=1000 -e GID=1000
 
-replacing 1000 with a UID that is present on the host.
-Here is one way to find the UID given a username:
+replacing 1000 with a UID and GID that is present on the host.
+Here is one way to find the UID and GID:
 
-    grep some_host_user /etc/passwd|cut -d: -f3
+    id some_host_user
+    getent group some_host_group
 
 ## Versions
 

minecraft-server/start-minecraft.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+umask 002
+
 if [ ! -e /data/eula.txt ]; then
   if [ "$EULA" != "" ]; then
     echo "# Generated via Docker on $(date)" > eula.txt

minecraft-server/start.sh

@@ -2,7 +2,10 @@
 
 set -e
 usermod --uid $UID minecraft
-chown -R minecraft /data /start-minecraft
+groupmod --gid $GID minecraft
+
+chown -R minecraft:minecraft /data /start-minecraft
+chmod -R g+wX /data /start-minecraft
 
 while lsof -- /start-minecraft; do
   echo -n "."