Systemd timers are a feature of the systemd init system on Linux that allows to schedule and automate tasks at specific intervals or times.

Query and View Timer Information

• View the active timers systemctl list-timers
• View the timer unit file contents systemctl cat fstrim.timer
• View the associated service unit file contents systemctl cat fstrim.service
• Analyse various timer notations:

	systemd-analyze calendar hourly
	systemd-analyze calendar daily
	systemd-analyze calendar weekly
	systemd-analyze calendar monthly
	systemd-analyze calendar "*-*-* 09..17:00/5"
	systemd-analyze calendar "Mon..Fri *-*-* 09..17:00/5"

Creating Timer event

• Create a timer unit file sudo systemctl edit --full --force [NAME].timer
• Edit the file.
• Create an associated service unit file sudo systemctl edit --full --force [NAME].service
• Edit the file as well.
• Create a script to be called by the service vim [NAME.sh]
• Enable and start the timer sudo systemctl enable [NAME].timer and sudo systemctl start blahwoof.timer
• Troubleshoot any issues. Look in the system journal to see if everything is OK journalctl --follow
• Make script executable chmod a+x ~/journo.sh

Updates by Timer for Debian

• Create service sudo vim /etc/systemd/system/update.service
• The this code inside

  [Unit] Description=Automated OS Update 
  [Service] ExecStart=/usr/bin/apt-get update && /usr/bin/apt-get dist-upgrade -y 
  Type=oneshot
  [Install] WantedBy=multi-user.target
  

• Create timer and reference service sudo vim /etc/systemd/system/update.timer

  [Unit]
   Description=Runs the update service every 5 days 
  [Timer]
  OnBootSec=1min OnUnitActiveSec=5d 
  Unit=update.service 
  [Install] 
   WantedBy=timers.target
  

• Enable and start sudo systemctl enable update.timer %% systemctl start update.timer