[mc] Added issues link

Document JVM_OPTS
For #176 and #177

minecraft-server/README.md

@@ -1,6 +1,7 @@
 
 [![Docker Pulls](https://img.shields.io/docker/pulls/itzg/minecraft-server.svg)](https://hub.docker.com/r/itzg/minecraft-server/)
 [![Docker Stars](https://img.shields.io/docker/stars/itzg/minecraft-server.svg?maxAge=2592000)](https://hub.docker.com/r/itzg/minecraft-server/)
+[![GitHub Issues](https://img.shields.io/github/issues-raw/itzg/dockerfiles.svg)](https://github.com/itzg/dockerfiles/issues)
 
 This docker image provides a Minecraft Server that will automatically download the latest stable
 version at startup. You can also run/upgrade to any specific version or the
@@ -710,3 +711,9 @@ The values of all three are passed directly to the JVM and support format/units
 ### /data ownership
 
 In order to adapt to differences in `UID` and `GID` settings the entry script will attempt to correct ownership and writability of the `/data` directory. This logic can be disabled by setting `-e SKIP_OWNERSHIP_FIX=TRUE`.
+
+### JVM Options
+
+General JVM options can be passed to the Minecraft Server invocation by passing a `JVM_OPTS`
+environment variable. Options like `-X` that need to proceed general JVM options can be passed
+via a `JVM_XX_OPTS` environment variable.

minecraft-server/start-minecraft.sh

@@ -9,6 +9,10 @@ if [ ! -e /data/eula.txt ]; then
   if [ "$EULA" != "" ]; then
     echo "# Generated via Docker on $(date)" > eula.txt
     echo "eula=$EULA" >> eula.txt
+    if [ $? != 0 ]; then
+      echo "ERROR: unable to write eula to /data. Please make sure attached directory is writable by uid=${UID}"
+      exit 2
+    fi
   else
     echo ""
     echo "Please accept the Minecraft EULA at"
@@ -20,6 +24,11 @@ if [ ! -e /data/eula.txt ]; then
   fi
 fi
 
+if ! touch /data/.verify_access; then
+  echo "ERROR: /data doesn't seem to be writable. Please make sure attached directory is writable by uid=${UID} "
+  exit 2
+fi
+
 SERVER_PROPERTIES=/data/server.properties
 FTB_DIR=/data/FeedTheBeast
 VERSIONS_JSON=https://launchermeta.mojang.com/mc/game/version_manifest.json