Step by Step

~$ cd /lib/systemd/system
~$ touch memory-notify.service
[Unit]
Description=memory-notify

[Service]
ExecStart=/bin/sh /home/ming/Project/Shell/memory-notify.sh
~$ touch memory-notify.timer
[Unit]
Description=Runs memory-notify every second

[Timer]
OnUnitActiveSec=1s
Unit=memory-notify.service

[Install]
WantedBy=multi-user.target
~$ sudo systemctl enable memory-notify.timer

Reference

• Systemd 定时器教程