Crontab - a quick glance
crontab is a powerful tool for automation. One of the most common usages nowadays is certification renewal, no matter using certbot or acme.sh.
Edit task
Edit crontab for current user
crontab -eEdit crontab for root user
sudo crontab -eEdit crontab for specific user
crontab -u <username> -eList task
crontab -l is used for this purpose
Test crontab rules
crontab.guru could be used for this purpose, which provides a nice visualized interface for either beginners or advanced users.
Crontab.guru - The cron schedule expression editor
An easy to use editor for crontab schedules.
The following examples can also be used for quick reference
Cron examples - Crontab.guru
Check if tasks are executed correctly
grep -i cron /var/log/syslog