Open crontab with nano

How to edit crontab or check the cron jobs in crontab :

To verify crontab :

sudo crontab -l

To backup crontab :

sudo crontab -l > crontab.bak

To edit crontab :

crontab -e

Or

nano /etc/crontab

You have also :

nano /etc/cron.daily
nano /etc/cron.weekly
nano /etc/cron.monthly