The uncertainty of "did this edit to the crontab file get seen by the daemon". The distinction between original Unix cron, anacron, and the at function. What

The uncertainty of "did this edit to the crontab file get seen by the daemon". The distinction between original Unix cron, anacron, and the at function. What PATH applies. Which POSIX are you on? Linux or BSD or SysV derived Unix differs in cron Is cron even running by default? Containerised Unix may not do what you think One syntax for /etc/cron.d (user to run as) and another for crontab -u <user> -e The variation in which file it logs to in /var/log Systemd and launchd and systemctl and launchctl and journalctl... (persisting daemons which run things according to the clock) Daylight savings and ritualised habits about cronojbs at midnight (Yes, I read the article. It's a great practical introduction to cron on most Linux situations people will find themselves in for the first time)