Ubuntu developers release updates of particular packages on a regular basis, those meant for security and bug fixing. It’s recommended to regularly upgrade the system. This is made by the consequence of two commands, united into a single one, for a handier use:
sudo apt-get update && sudo apt-get upgrade -y
This action must be performed by a user with root rights.
In case of import from the OVA-appliance this user is support. Upgrade can take some time, the more time passed from the moment of OVA-image creation or the latest update. In average, update takes a few minutes. It also requires acces to the internet.
When the update is completed the following commands may be run
sudo apt-get autoclean && sudo apt-get autoremove
They help to remove unused packages if any, and to clean the archive of packages.