Start service on bootup

/etc/systemd/system/onbootup.service

[Unit]
Description=OnBootup

[Service]
ExecStart=/usr/bin/bash /usr/local/bin/onbootup.sh

[Install]
WantedBy=multi-user.target

/usr/local/bin/onbootup.sh

#!/usr/bin/bash
logger "Hello"

Run service with a timer

[Unit]
Description=My service

[Timer]
OnCalendar=daily
Persistent=true

[Install]
WantedBy=timers.target