Tonight I was updating an Ubuntu server to 12.04LTS using
do-release-upgrade.
It failed, because of a problem with my locale. Normally I use LANG=C to avoid some unpleasantness for a programming environment, but it was set to en_GB.UTF-8, which confused the libc update, aborting the upgrade and leaving the system in a highly inconsistent state. Wonderful.
A quick Google found a way round it:
apt-get -o APT::Immediate-Configure=0 -f install
which was fine (no, I've no idea either), and I'd set LANG=C just in case, but because I was using 9term, the apt-get initially failed with:
Unknown terminal: 9term
Check the TERM environment variable.
Also make sure that the terminal is defined in the terminfo database.
Alternatively, set the TERMCAP environment variable to the desired termcap entry.
debconf: whiptail output the above errors, giving up!
I wasn't quite sure how to "whiptail" output (sounds a bit saucy, frankly) but guessed correctly that I could simply set TERM=dumb. After that, the upgrade completed.
If it had a terminal it didn't understand, why didn't it do that itself?
Even then, it ends up moaning:
debconf: unable to initialize frontend: Dialog
debconf: (Dialog frontend will not work on a dumb terminal, an emacs shell buffer, or without a controlling terminal.)
debconf: falling back to frontend: Readline
It's surely bad enough that TERM and TERMCAP still exist: they are choosing between different emulations of devices that are more than 30 years old! You'd think we could have one emulated archaic device and be done with it. Even sillier we've apparently got applications that act as if you've taken away their Zimmer frames if you don't give them the right emulated device.
