Adding a Custom systemd Service¶

How to define, install, enable, and debug a custom systemd service.

This English edition keeps the original illustrations and reproducible command or configuration examples.

Reference diagram 1

Reference diagram 2

Reference diagram 3

Commands and configuration¶

#!/bin/sh
echo "Hello, I am Hywelstar, This is a demo!"

chmod +x /home/root/hywelstar_script.sh

sudo vi /etc/systemd/system/hywelstar_service.service

[Unit]
Description=Hywelstar Demo Service
After=network.target

[Service]
ExecStart=/home/root/hywelstar_script.sh
Restart=on-failure

[Install]
WantedBy=multi-user.target

sudo systemctl daemon-reload

sudo systemctl enable hywelstar_service.service

sudo systemctl start hywelstar_service.service

sudo systemctl status hywelstar_service.service

● hywelstar_service.service - Hywelstar Demo Service
   Loaded: loaded (/etc/systemd/system/hywelstar_service.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Fri 2021-09-24 01:40:47 UTC; 1min 8s ago
  Process: 9820 ExecStart=/home/root/hywelstar_script.sh (code=exited, status=0/SUCCESS)
 Main PID: 9820 (code=exited, status=0/SUCCESS)

Sep 24 01:40:47 UserDevice systemd[1]: Started Hywelstar Demo Service.
Sep 24 01:40:47 UserDevice hywelstar_script.sh[9820]: Hello, I am Hywelstar, This is a demo!

sudo systemctl stop hywelstar_service.service
sudo systemctl disable hywelstar_service.service

sudo journalctl -u hywelstar_service.service

Practical notes¶

Test each change on a recoverable target, keep logs from the boot or failure path, and record the exact kernel and userspace versions used in the result.