pin FROM to use 8-jdk-bullseye

Dockerfile

@@ -1,10 +1,14 @@
-FROM openjdk:latest
+FROM openjdk:8-jdk-bullseye
+
+RUN apt update && apt install -y unzip
 
 RUN groupadd -r minecraft -g 2000
 RUN useradd --no-log-init minecraft -u 2000 -g 2000 -m
 WORKDIR /mc_data
 RUN chown -R minecraft:minecraft .
 
+# Copy the modpack
+COPY the-1122-pack/the-1122-pack_1.3.7.zip /the-1122-pack/the-1122-pack_1.3.7.zip
+RUN chown -R minecraft:minecraft /the-1122-pack
+
 USER minecraft
-# Copy files only if they don't yet exist (server.jar, server.properties, etc) and start the server
-CMD java -Xmx"$MAX_RAM"G -Xms"$MIN_RAM"G -jar ./server.jar nogui