systemd: start service at boot added

wiki/linux/systemd.md

@@ -0,0 +1,30 @@
+# SystemD
+
+SystemD is a software suit for system components for Linux systems.
+It is mainly used for service configuration.
+
+## Run command on boot
+
+To run a command (in this case `/bin/bash /root/run.sh`) create the following
+file at `/etc/systemd/system/` with a name ending on `.service`.
+In this case it is called `unturned.service`.
+
+```txt
+[Unit]
+Description=Description of the service
+
+[Install]
+WantedBy=multi-user.target
+
+[Service]
+ExecStart=/bin/bash /root/run.sh
+Type=simple
+```
+
+For [Proxmox](./proxmox.md) you can add the following line under the `[Unit]`
+section to make sure the service is started after Proxmox has finished
+initializing.
+
+```txt
+After=pve-guests.service
+```