Crontab not available

[JohanBraeken]

Crontab is used for various scheduled tasks and is currently unavailable.

Ex:
If DNSSEC is configured, you can not use the automatic resigning feature in Webmin.
Enabling it results in the following message:

Failed to save DNSSEC key re-signing : Cron jobs cannot be managed on your system, as the module configuration is not valid : The command crontab for managing user Cron configurations was not found. Maybe Cron is not installed on this system?