sudo apt install openjdk-8-jre-headless screen xinetd
sudo adduser --system --group --home /opt/minecraft minecraft
Download Minecraft Server to /opt/minecraft and rename server JAR as server.jar
Set server-port=25555 in server.properties
Copy start.sh and stop.sh to /opt/minecraft and make them executable
sudo -u minecraft /usr/bin/java -Xms1024M -Xmx1536M -jar server.jar nogui
The Minecraft server should start and then stop saying the EULA needs to be accepted.
Set eula=true in /opt/minecraft/eula.txt
Copy minecraft to /etc/xinetd.d
sudo systemctl restart xinetd
Add */5 * * * * /opt/minecraft/stop.sh to crontab for user minecraft (sudo crontab -u minecraft -e)
xinetd daemon is listening on the default Minecraft Server port (25565). When a client connects, xinetd runs /opt/minecraft/start.sh, which, on the first connection, spawns the Minecraft Server (configured to listen on port 25555) using screen and then executes netcat to send/receive traffic from the client on port 25565 to the Minecraft Server on port 25555 via the loopback interface.
The cron job runs every five minutes, checks whether the Minecraft server is running and if so issues the list server command to check whether there are any active users. If not, then after waiting two minutes and checking again, the server is stopped. If there are active users, the script prints a random comedy message (this can be commented out if not needed).