I tried both aptitude -y safe-upgrade and apt-get upgrade -f but in both cases, I get:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
... (long list)
0 packages upgraded, 0 newly installed, 0 to remove and 903 not upgraded.
I guess this resulted from several hacks where I tried to update my system (trying to work around this problem).
My question now: Why are they kept back? What can I do to install them?
On a similar question, I got the suggestion to just use apt-get dist-upgrade instead. However, that fails at the moment for me because of:
E: Could not perform immediate configuration on 'util-linux'.Please see man 5 apt.conf under APT::Immediate-Configure for details. (2)
This is this problem.
After I did
sudo apt-get install libc6-dev(because), this resolved all the kept-back packages (well, or maybe it was myapt-get dist-upgradewhich I did after that, which failed though).