Update the Dockerfile for readability

- Make the download/verify section more readable
- Add JVM_OPTS to CMD
- Use ARG EULA during the build
- Update build instructions in README

Dockerfile

@@ -1,9 +1,9 @@
 FROM debian:stable
 
-ENV DEBIAN_FRONTEND=noninteractive
 ENV VERSION=1.20.1
 ENV JVM_OPTS="-Xmx2G -Xms1G"
-ENV EULA=false
+ENV DEBIAN_FRONTEND=noninteractive
+ARG EULA=false
 
 # Install dependencies
 RUN apt-get update && \
@@ -21,17 +21,21 @@ RUN mkdir /app && \
 
 # Download and verify sha1sum for server.jar
 WORKDIR /app
-RUN curl -s https://launchermeta.mojang.com/mc/game/version_manifest.json \
-  | jq -r --arg id "$VERSION" '.versions[] | select(.id == $id) | .url' | xargs curl -s \
-  | jq -r '.downloads.server' | tee "/tmp/dl.json" | jq -r '.url' | xargs curl -s -o server.jar \
-  && sha1sum server.jar | awk '{print $1}' | xargs -I{} sh -c '[ "{}" = "$(jq -r .sha1 /tmp/dl.json)" ] && \
-  (echo "Checksum matches" && rm /tmp/dl.json) || (echo "Checksum failed" && exit 1)' \
-  && chown minecraft:minecraft server.jar
-
 USER minecraft
+RUN set -ux; \
+  # Get server.jar based on $VERSION
+  curl -s https://launchermeta.mojang.com/mc/game/version_manifest.json \
+  | jq -r --arg id "$VERSION" '.versions[] | select(.id == $id) | .url' | xargs curl -s \
+  | jq -r '.downloads.server' | tee "/tmp/dl.json" | jq -r '.url' | xargs curl -s -o server.jar && \
+  java -jar server.jar --initSettings --nogui && \
+  sed -i "s/^eula=.*\$/eula=$EULA/" eula.txt && \
+  # Get SHA1 hash of server.jar and compare
+  SHA1="$(sha1sum server.jar | awk '{print $1}')" && \
+  EXPECTED="$(jq -r .sha1 /tmp/dl.json)"; rm /tmp/dl.json && \
+  if [ ! "$SHA1" = "$EXPECTED" ]; then \
+    echo "[ERROR] SHA1=\"$SHA1\" expected \"$EXPECTED\""; \
+    exit 1; \
+  fi
+
 EXPOSE 25565
-
+CMD ["java", "-jar", "server.jar", "$JVM_OPTS", "--nogui"]
-# temp
-RUN echo 'eula=true' > eula.txt
-
-CMD ["java", "-jar", "server.jar", "nogui"]

README.md

@@ -4,7 +4,9 @@ This Dockerfile sets up a Minecraft server based on Debian stable. WIP.
 
 To test image creation, run:
 ```
-docker build . -t minecraft:vanilla; docker run -d minecraft:vanilla
+docker build --build-arg EULA=true -t minecraft . && \
+docker run -d --name minecraft --rm minecraft && \
+docker logs -f minecraft
 ```
 
 ## Copyright and License