crontab cheat sheet (Ubuntu)
User crontab editing and examples.
Edit & list
crontab -e
crontab -l
crontab -r
Schedule examples (5 fields)
minute hour day month weekday command
0 3 * * * /usr/local/bin/backup.sh
0 * * * * /path/to/hourly.sh
0 0 * * 0 /path/to/weekly.sh
System cron
ls /etc/cron.d/