Refactor image, Java sourcing, and add entrypoint

- Moved to debian-slim base image to minimize size
- Transitioned to Adoptium APT repos for flexibility in Java versions
- Added an entrypoint script that configures EULA and server settings
- Run server in resumable screen for console access in the container

Dockerfile

@@ -1,34 +1,62 @@
-FROM debian:stable
+FROM debian:stable-slim
 
-ENV VERSION=1.20.1
-ENV JVM_OPTS="-Xmx2G -Xms1G"
+ARG VERSION=latest
+ARG JAVA_VERSION=latest
 ENV DEBIAN_FRONTEND=noninteractive
-ARG EULA=false
-
-# Install dependencies
-RUN apt-get update && \
-    apt-get install -y curl default-jre jq && \
-    apt-get clean && \
-    rm -rf /var/lib/apt/lists/*
 
 # Create minecraft user
 RUN groupadd -g 1000 minecraft && \
-    useradd -m -u 1000 -g 1000 -d /home/minecraft minecraft
+    useradd -m -u 1000 -g 1000 -d /app minecraft
 
-# Create directory
-RUN mkdir /app && \
-    chown minecraft:minecraft /app
+# Install scripting dependencies
+RUN apt-get update && \
+    apt-get install -y curl gpg jq screen && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+# Eclipse Adoptium DEB installer package
+RUN set -ux && \
+  # Download the Eclipse Adoptium GPG key
+  curl -s https://packages.adoptium.net/artifactory/api/gpg/key/public \
+    | gpg --dearmor | tee /etc/apt/trusted.gpg.d/adoptium.gpg > /dev/null && \
+  # Configure the Eclipse Adoptium apt repository
+  VERSION_CODENAME="$(awk -F= '/^VERSION_CODENAME/{print $2}' /etc/os-release)" && \
+  echo "deb https://packages.adoptium.net/artifactory/deb $VERSION_CODENAME main" \
+    | tee /etc/apt/sources.list.d/adoptium.list
+
+# Install Adoptium Temurin (OpenJDK Distribution)
+RUN set -ux && \
+  # Grab latest LTS version if not specified
+  if [ "$JAVA_VERSION" = "latest" ]; then \
+    JAVA_VERSION="$( \
+      curl -s https://api.adoptium.net/v3/info/available_releases \
+        | jq '.most_recent_lts' \
+    )"; \
+  fi && \
+  # Install the Temurin version
+  apt-get update && \
+  apt-get install -y "temurin-${JAVA_VERSION}-jre" && \
+  apt-get clean && \
+  rm -rf /var/lib/apt/lists/*
+
+# Download files and run as user
+USER minecraft
+WORKDIR /app
 
 # Download and verify sha1sum for server.jar
-WORKDIR /app
-USER minecraft
-RUN set -ux; \
+RUN set -ux && \
+  # Grab latest version if not specified
+  if [ "$VERSION" = "latest" ]; then \
+    VERSION="$( \
+      curl -s https://launchermeta.mojang.com/mc/game/version_manifest.json \
+        | jq -r '.latest.release' \
+    )"; \
+  fi && \
   # 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 && \
+    | jq -r --arg id "$VERSION" '.versions[] | select(.id == $id) | .url' \
+    | xargs curl -s | jq -r '.downloads.server' | tee "/tmp/dl.json" \
+    | jq -r '.url' | xargs curl -s -o server.jar && \
   # Get SHA1 hash of server.jar and compare
   SHA1="$(sha1sum server.jar | awk '{print $1}')" && \
   EXPECTED="$(jq -r .sha1 /tmp/dl.json)"; rm /tmp/dl.json && \
@@ -37,5 +65,21 @@ RUN set -ux; \
     exit 1; \
   fi
 
+# Generate initial settings
+RUN java -jar server.jar --initSettings --nogui
+
+# Back to root to copy the entrypoint in
+USER root
+WORKDIR /app
+
+# Copy in entrypoint script
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+
+# Run app as minecraft user
+USER minecraft
+WORKDIR /app
+
+# Expose port and run entrypoint script
 EXPOSE 25565
-CMD ["java", "-jar", "server.jar", "$JVM_OPTS", "--nogui"]
+ENTRYPOINT ["entrypoint.sh"]