Cron jobs are specific tasks that you can schedule in crobtab. Crontabs is useful for executing jobs automatically in backend.
crontab is a command used to manage cron jobs for all users. To manually edit a crontab you can use either crontab -e or edit /etc/crontab
The cron jobs for specific users are located in /var/spool/cron/username. You can also schedule your cron jobs by hourly,daily,weekly, and monthly by directing them to:
/etc/cron.hourly /etc/cron.daily /etc/cron.weekly /etc/cron.monthly
As mentioned earlier, you can access crontabs by crontab -e or edit /etc/crontab
run-parts will run every script within that directory. In this case it will run /etc/cron.hourly, /etc/cron.daily ,/etc/cron.weekly,/etc/cron.monthly
As you can see that syntax for each line:
minutes hour day of month month day of week username command
Lets take the fist example:
37 Minutes, Every Hour, Every Day of month , every month, every day of week, username: root, command run-parts /etc/cron.hourly
-e Edit your crontab file, or create one if it doesn't already exist.
-l Display your crontab file.
-r Remove your crontab file.
-u user Used in conjunction with other options, this option allows you to modify or view the crontab file of user. When available, only administrators can use this option.
1. Edit your cron tab
crontab -e
2. Display your crontab
crontab -l
3. Remove your crontab
crontab -r
5. Edit user1 crontab file
crontab -eu user1
6. List user1 crontab file
crontab -lu user1
7. Remove user1 crontab file
crontab -ru user1
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