Package post-install notification methods?

[Jani Monoses]

Hello,

I received quite a few helpful suggestions about how one could partially 
solve the problem I describe below so I am more confused than if there 
were only one way to do it :)

For an ARM blueprint [1] concerning updating boot firmware on certain 
boards, one of the requirements is to notify users when a new bootloader 
package is installed. These binary packages (u-boot and/or x-loader) get 
installed on the system but they have no effect on the booting unless 
the files they contain are copied to a boot partition.

This copying is not automatic and not part of the package via a dpkg 
hook because it is a potentially dangerous operation. However users 
should be notified that the possibility exists and that they can flash 
the new firmware using flash-kernel.

The question is how to present this notification to the user so that
* it works both in X and in headless images
* it is simple and involves a minimum number of package and system file 
changes :)

I was suggested motd-update, jockey, update-manager hooks and debconf 
notes so far.

I find the debconf way the least intrusive but I worry that few packages 
use such notes and it is only for important use-cases.

Such firmware updates do not happen frequently, if ever, in a stable 
release, as only bugfixes that cannot otherwise be worked around in 
kernel or userland are targeted.

thank you
Jani

[1] 
https://launchpad.net/ubuntu/+spec/other-arm-n-handle-core-boot-files-update