Upgrade to cups-bsd_1.4.3-1ubuntu1.2 hangs during preseeded install

Confirmed exact same symptoms attempting the same sort of preseed upgrade during an install of Ubuntu 10.10

I have not figured out why it was hanging, but I have discovered that wrapping the call in debconf-apt-progress not only presents a proper progress bar, but also somehow avoids the hang.

So, my full late_command is:

d-i preseed/late_command string in-target sh -c "debconf-apt-progress --logstderr -- aptitude -q --without-recommends -y -o DPkg::options=--force-confnew full-upgrade"

(The options that I'm using are there because I copied them from the pkgsel code handling the pkgsel/upgrade step.)

The hanging process is part of debconf, seems to be a debconf bug. Moving to debconf ...

We probably need a trace with DEBCONF_DEBUG=developer set in the environment in order to do anything about this. (And usually this kind of thing is a package bug anyway.)

Actually, this rings a bell and I know what the problem is. cups-bsd.prerm executes update-inetd, which uses debconf. Normally, you can use debconf in child processes without a problem. However, because of some odd bits in the way the debconf shell and Perl bindings work together, if cups-bsd.prerm is being run from within something that uses debconf (debconf-apt-progress, in this case), IIRC the only way update-inetd is going to work properly is if cups-bsd.prerm sources the debconf confmodule; otherwise it will send debconf commands to the wrong place. I know this is a bit weird since cups-bsd.prerm doesn't itself use debconf directly.

In short, I think this will go away if you ensure that cups-bsd.prerm does '. /usr/share/debconf/confmodule' at the very top, immediately below 'set -e'. You'll need to test that, though.

Actually, the problem does not occur when debconf-apt-progress is involved.

The hang occurs if aptitude is invoked directly from preseed/late_command. Wrapping the aptitude call in debconf-apt-progress seems to somehow perturb the debconf communications sufficiently that it does not hang.