Notify more than three kernel images installed to prevent full boot partition

[Pander]

The boot partition could fill up when more and more kernels are automatically being installed. In order to notify the administrator of a system, provide an option to notify when more than three kernel images are installed.

One option should be added to activate this behavior. The threshold for when this notification is being send should be overridden by a second parameter that has a default of three. The content of the notification should be very short.

If it could be a security hazard, do not list the installed kernel image versions and do not list the amount of free disk space on the boot partition. Simply notify the number of kernels that are installed and report the threshold and the risk that no new kernels cannot be installed unattended when boot partition runs out of disk space.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Pander (pander)]

In another form also reported upstream for package unattended-upgrades

[Pander (pander)]

Notification could be:
- email
- in Ububtu upgrade dialogue that appears when user has to initiate updrades