While working with my Ubunu JeOS 8.04 appliance I found out that crontab was missing and not included with default installation . Crontab is linux scheduler to run things on specific times you define.

Cron is a daemon used for scheduling tasks to be executed at a certain time. Each user has a crontab file, allowing them to specify actions and times that they should be executed. There is also a system crontab, allowing tasks such as log rotation and locate database updating to be done regularly.  Read more here.

-bash: crontab: command not found Oeps seems it is missing on my vm. 

To install it run:

• sudo apt-get install cron