Interesting, I didn't remember this. It's the same on my 18.04 machine. And according to etckeeper it has been like this since the installation. But systemd-res

Interesting, I didn't remember this. It's the same on my 18.04 machine. And according to etckeeper it has been like this since the installation. But systemd-resolved is running, that's not a very consistent system configuration is it? /etc/resolv.conf is a symbolic link to something generated by systemd-resolved. So in this case we can indeed say that systemd-resolved controls /etc/resolv.conf and the latter is really used by the rest of the system. No idea why anybody would intentionally use systemd-resolved this way or whether it is really just a bug. The bug report has been open for nearly a year and it looks like no Ubuntu core developer has commented. Unfortunately all too common in launchpad :( The root cause for "resolve" not being in /etc/nsswitch.conf is libnss-resolve not being installed. It seems to be completely optional with nothing pulling it in. In my 16.04 systemd-resolved is not even running. That's what I would have expected.