Knowing systemd is useful for automating many tasks in Linux.
Running Services as User
Running services as a user instead of root is beneficial in many cases.
For example, we may want to run Music Player Daemon (mpd) on startup as a user in order to use user configuration files instead of the global ones. In this case, we must first disable the default service, and re-enable it as user:
systemctl stop mpd.service
systemctl disable mpd.service
systemctl --user enable mpd.service
Creating Systemd Services
User services are stored under: ~/.config/systemd/user/. Place any custom scripts that you write in this folder.
Here is an example change-GTK-theme.service, which changes my computer’s GTK theme to dark mode:
[Unit]
Description=Change the GTK theme to dark mode.
After=graphical.target
[Service]
Type=oneshot
ExecStart=/bin/sh -c 'gsettings set org.gnome.desktop.interface gtk-theme Adwaita-dark && gsettings set org.gnome.gedit.preferences.editor scheme builder-dark'
[Install]
WantedBy=default.target
Scheduling Systemd Tasks
Systemd can be used as a more powerful alternative to cron jobs.
To do this, you need to create two files: my-service.service, and a my-service.timer, both files must have the same root name.
Example timer file:
[Unit]
Description=Change the GTK theme daily at a given time.
[Timer]
OnCalendar=*-*-* 16:00:00
Persistent=true
[Install]
WantedBy=timers.target
This timer runs the change-GTK.service shown previously every day at 16:00 hrs.
For more on timers: https://wiki.archlinux.org/index.php/Systemd/Timers