Add support for level type and generator settings

minecraft-server/Dockerfile

@@ -2,7 +2,7 @@ FROM itzg/ubuntu-openjdk-7
 
 MAINTAINER itzg
 
-ENV APT_GET_UPDATE 2015-03-28
+ENV APT_GET_UPDATE 2015-10-03
 RUN apt-get update
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y libmozjs-24-bin imagemagick && apt-get clean
@@ -31,4 +31,5 @@ ENV MC_IMAGE=YES
 ENV UID=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
+ENV TYPE=VANILLA VERSION=LATEST FORGEVERSION=RECOMMENDED LEVEL=world PVP=true DIFFICULTY=easy \
+  LEVEL_TYPE=DEFAULT GENERATOR_SETTINGS=

minecraft-server/README.md

@@ -183,11 +183,32 @@ message of the day that contains spaces by putting quotes around the whole thing
 
 ### PVP Mode
 
-By default servers are created with player-vs-player (PVP) mode enabled. You can disable this with the `PVP`
+By default, servers are created with player-vs-player (PVP) mode enabled. You can disable this with the `PVP`
 environment variable set to `false`, such as
 
     docker run -d -e PVP=false ...
 
+### Level Type and Generator Settings
+
+By default, a standard world is generated with hills, valleys, water, etc. A different level type can
+be configured by setting `LEVEL_TYPE` to
+
+* DEFAULT
+* FLAT
+* LARGEBIOMES
+* AMPLIFIED
+* CUSTOMIZED
+
+Descriptions are available at the [gamepedia](http://minecraft.gamepedia.com/Server.properties).
+
+When using a level type of `FLAT` and `CUSTOMIZED`, you can further configure the world generator
+by passing [custom generator settings](http://minecraft.gamepedia.com/Superflat). 
+**Since generator settings usually have ;'s in them, surround the -e value with a single quote, like below.**
+
+For example (just the `-e` bits):
+
+    -e LEVEL_TYPE=flat -e 'GENERATOR_SETTINGS=3;minecraft:bedrock,3*minecraft:stone,52*minecraft:sandstone;2;'
+
 ### World Save Name
 
 You can either switch between world saves or run multiple containers with different saves by using the `LEVEL` option,

minecraft-server/server.properties

@@ -30,4 +30,4 @@ generate-structures=true
 view-distance=10
 spawn-protection=16
 motd=A Minecraft Server powered by Docker
-
+generator-settings=

minecraft-server/start-minecraft.sh

@@ -105,6 +105,25 @@ if [ ! -e server.properties ]; then
     sed -i "/pvp\s*=/ c pvp=$PVP" /data/server.properties
   fi
 
+  if [ -n "$LEVEL_TYPE" ]; then
+    # normalize to uppercase
+    LEVEL_TYPE=${LEVEL_TYPE^^}
+    # check for valid values and only then set
+    case $LEVEL_TYPE in
+      DEFAULT|FLAT|LARGEBIOMES|AMPLIFIED|CUSTOMIZED)
+        sed -i "/level-type\s*=/ c level-type=$LEVEL_TYPE" /data/server.properties
+        ;;
+      *)
+        echo "Invalid LEVEL_TYPE: $LEVEL_TYPE"
+	exit 1
+	;;
+    esac
+  fi
+
+  if [ -n "$GENERATOR_SETTINGS" ]; then
+    sed -i "/generator-settings\s*=/ c generator-settings=$GENERATOR_SETTINGS" /data/server.properties
+  fi
+
   if [ -n "$DIFFICULTY" ]; then
     case $DIFFICULTY in
       peaceful)