packages been kept back

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.

Solution 1:

After I did sudo apt-get install libc6-dev (because), this resolved all the kept-back packages (well, or maybe it was my apt-get dist-upgrade which I did after that, which failed though).