At mini-Debconf Cambridge:
Much unintentional chaos and hilarity and world class problem solving yesterday.
A routine upgrade from Wheezy - Jessie died horribly on my laptop when UEFI variable space filled, leaving No Operating System on screen.
Cue much running around: Chris Boot, Colin Walters, Steve dug around, booted the system usng rescue CD and so on. Lots more digging, including helpful posts by mjg59 - a BIOS update may solve the problem.
Flashing BIOS did clear the variables and variable space and it all worked perfectly thereafter. This had the potential for turning the laptop into a brick under UEFI (but still working under legacy boot).
As it is, it all worked perfectly - but where else would you get _the_ Grub maintainer, 2 x UEFI experts and a broken laptop all in the same room ?
If it hadn't happened yesterday, it would have happened at home and I'd have been left with nothing. As it is, we all learnt/remembered stuff and had a useful time fixing it.