ntp asks to keep or replace ntp.conf

This is how conffile changes are handled in the Debian (Ubuntu) package management system. It's not a ntp bug.

Ok, but it is still a bug! I have now added that it affects debian-installer rather than marking it just invalid.

Actually it would be dpkg, but it's still how the system is designed to work. I'll let someone who routinely works on dpkg mark it won't fix.

Automatically assuming a user wants a specific action done to their customised config files is Just Plain Wrong, and we will never do it, however if *you* want something specific done to yours, you may add "force-confold" "force-confdef", etc (see "man dpkg" for force options, and "man dpkg.cfg" for what to do with them) to /etc/dpkg/dpkg,cfg

We give you the rope to hang yourself on this one, but we're not prepared to tie it around your neck without your permission. :)

So in reference to Adam's comment, can we do something better for the user? Best usability surely implies that as per my original 3rd point, that questions of the user should occur at the beginning or end of the upgrade. I don't believe repeated interruptions during the upgrade give a good feeling. Ideally all questions can be asked at the beginning, that way a user is going to be sure he has gathered all the information prior to committing to an upgrade. Sure, this might mean a rearchitecture of the debian-installer or dpkg even, but I think it should be investigated. The main reason I never got into Debian a few years ago was the fact that the install process took so long as you never were quite sure you weren't going to be asked more questions. Certainly for fresh installs Ubuntu has this sorted, but my concern is during an upgrade, people often allocate time to do this, walk away at the beginning of installation and hope to come back in 30 minutes and find it done. The current architecture does not seem to allow this.

There is a mechanism for asking questions before an install (debconf), and ntp could certainly use debconf and mangle its own config files, instead of marking them as dpkg conffiles. As I recall, it used to do so, actually, and the maintainers opted for a different approach at some point in the last few years.

Ubuntu isn't terribly likely to deviate from Debian on this one (as maintaining a retro-fit debconf patch on every sync can be tedious), but you're welcome to file a bug on ntp in Ubuntu and in Debian asking for debconf-managed config files.

To the usability argument, however, realistically, most people won't ever have a changed ntp.conf (or even have ntpd installed), and "usability" tends to speak of the "average user", not corner cases. There are hundreds, if not thousands of dpkg conffiles in /etc, and seasoned Debian/Ubuntu sysadmins (the sorts of people who tend to mangle things in /etc by hand) tend to be used to dpkg conffile prompts.