What to do now? update just after install

Question

Configuration file '/etc/psd.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ?  Your options are:
    Y or I  : install the package maintainer's version
    N or O  : keep your currently-installed version
      D     : show the differences between the versions
      Z     : start a shell to examine the situation
 The default action is to keep your current version.
*** psd.conf (Y/I/N/O/D/Z) [default=N] ? n 

1421086511166   addons.repository   WARN    Unknown type id when parsing addon: 5
1421086511170   addons.repository   WARN    Unknown type id when parsing addon: 5
1421086512463   addons.update-checker   WARN    Update manifest for {972ce4c6-7e08-4474-a285-3208198ce6fd} did not contain an updates property
1421086512713   addons.update-checker   WARN    Update manifest for ubufox@ubuntu.com did not contain an updates property

No bp log location saved, using default.
[000:000] Cpu: 6.37.5, x4, 2399Mhz, 3753MB
[000:000] Computer model: Not available
[000:000] Browser XEmbed support present: 1
[000:000] Browser toolkit is Gtk2.
[000:001] Using Gtk2 toolkit

Answer 1

It means that a package update contains a newer version of a configuration file, but the package manager doesn't want to overwrite the changes you made to the old version. Therefore it invokes the program ucf(1), which gives you the choice to either

1. overwrite the old file (N or O) or
2. retain the old file (Y or I).

In both cases the other version will be saved to a file with the respective suffix *.ucf-old or *.ucf-new, which gives you the chance to later inspect the differences and change, revert, and/or update things according to your needs. *.ucf-dist holds the original content of the configuration file in the previous package version (before you changed it).

The final two options (D and Z) allow you to inspect the changes or the larger “situation” before making a decision. When you exit the diff viewer or the shell, you'll return to the same dialogue.