Add minecraft systemd article

content/tech/minecraft-systemd-start-script/index.md

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+---
+date: "2024-12-19"
+tags:
+- tech
+- minecraft
+- systemd
+---
+# Simple Minecraft systemd startup script
+
+Sometimes you just want to run a Minecraft server on your server, but you don't want to run it in a screen session, or you want to run it as a different user. This is where systemd comes in.
+
+## Goals
+
+* Run the Minecraft server as a different user
+* Be able to stop the server
+* Be able to start the server
+* Be able to see the server logs
+* Enable the server to start on boot
+* Properly shutdown the server on system shutdown without corruption
+
+Bash itself is not flexible enough to create a safe wrapper script. You can do things with unconnected pipes, but minecraft does not like unconnected pipes. If you try to connect a pipe, you either will be unable to capture the exit code, or make the script needlessly complicated
+
+I came up with the following solution using a python wrapper script instead (my server is stored in `/home/minecraft/server` and the server jar is `server.jar`)
+
+## Files
+
+`/etc/systemd/system/minecraft.service`
+
+```ini
+[Unit]
+Description=Run minecraft server
+After=network.target
+
+[Service]
+Restart=always
+RestartSec=5
+KillMode=mixed
+ExecStart=/root/server/minecraft-via-systemd
+WorkingDirectory=/home/minecraft/server
+User=minecraft
+
+[Install]
+WantedBy=multi-user.target
+```
+
+`/root/server/minecraft-via-systemd`
+
+```python
+#!/usr/bin/env python3
+import signal
+import subprocess
+
+java_process = subprocess.Popen(["./start.sh"], stdin=subprocess.PIPE)
+# java_process.stdin.write(b"op <your user name>\n")
+
+def handle_signal(signum, frame):
+  java_process.stdin.write(b"stop\n")
+  java_process.stdin.flush()
+
+signal.signal(signal.SIGTERM, handle_signal)
+signal.signal(signal.SIGINT, handle_signal)
+
+status_code = java_process.wait()
+exit(status_code)
+```
+
+We now need to define the start script for the server, in this case, I am using a simple shell script that starts the server with 1GB of memory
+
+`/home/minecraft/server/start.sh`
+
+```sh
+#!/bin/sh -ex
+exec java -Xmx1024M -Xms1024M -jar server.jar
+```
+After we created all these files, the last step is to enable the service, do not forge tto place your server jar in the server directory, together with a file to accept the EULA
+
+```sh
+systemctl daemon-reload # This is needed to load the new service file
+systemctl enable minecraft # This will enable the service to start on boot
+systemctl start minecraft # This will start the service now
+journalctl -fu minecraft # This will show the logs of the server in real time, so we can see the server starting
+```
+
+## Commands
+
+Since you might not been familiar with systemd, here are some commands to help you manage the server:
+
+* Check the status of the server: `systemctl status minecraft`
+* Start the server: `systemctl start minecraft`
+* Stop the server: `systemctl stop minecraft`
+* Restart the server: `systemctl restart minecraft`
+* See the logs: `journalctl -u minecraft`
+* See a live view of the logs: `journalctl -fu minecraft`
+* Enable the server to start on boot: `systemctl enable minecraft`
+* Disable the server to start on boot: `systemctl disable minecraft`