Comment 16 for bug 1796193

From a xenial system, I tried upgrading to bionic with do-release-upgrade with -f DistUpgradeViewNonInteractive and *not* setting up the force-confdef option, and it asks for input

Here's where it got stuck waiting for input:

Configuration file '/etc/ntp.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.
*** ntp.conf (Y/I/N/O/D/Z) [default=N] ?