Comment 18 for bug 222761

         if [ -z `getent group nut` ]; then
                 addgroup --quiet --system nut
-# else
-# printf "error: user \"nut\" already exists... see /usr/share/doc/nut/README.Debian\n" && exit 1
+ else
+ printf "skipping: user \"nut\" already exists... see /usr/share/doc/nut/README.Debian\n"
         fi
 }

Chuck, can you please explain how that changes the behavior? As far as I can see, this patch just triggers an additional warning message to appear (which is not good packaging, anyway; it will hardly be noticed). Steve, what was "the problem" when you tested upgrade? Did the upgrade fail (i. e. did addgroup error out because the group already existed), or was the problem that an already existing nut user isn't in some important group?

The nut user and group should *not* be removed on purging the package, BTW. That's common and good Debian practice for daemons which create files or processes owned by that system user. Otherwise the uid/gid would be recycled on next adduser, and existing files/processes would get owned by that new user.