[Bug 1817903] Re: systemd-resolve appends "options edns0" to resolv.conf

[Dan Streetman]

Ok I have found what the problem is, I think; I suspect that you have
resolvconf installed on your system, which is taking over the
/etc/resolv.conf file, and I think that resolvconf is pulling the edns0
option, but also including external nameserver(s), which is an incorrect
configuration, since the edns0 option should only be used when talking
to the local stub resolver, because we don't know if external dns
server(s) support edns.

The resolvconf package is not installed by default for Bionic (though I
am not sure if Mint installs it by default for some reason).  Is this
system upgraded from a previous release, or did you install resolvconf
manually?  Unless you specifically need it, can you try unistalling
resolvconf and rebooting to see if that fixes the problem for you?

$ sudo apt remove resolvconf
$ sudo reboot

And also please do paste the contents of /etc/resolv.conf here,
especially if removing resolvconf doesn't help.

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Title:
  systemd-resolve appends "options edns0" to resolv.conf

Status in systemd package in Ubuntu:
  New

Bug description:
  Mint 19 (Ubuntu 18.04)

  Following latest mint update done on 24/02/2019, DNS is broken....

  nslookup and dig of certain domain names work as expected, ping does
  not (ip works but not domain name)

  After a day of trial and error, testing I found that the problem lies
  with the presence of

  "options edns0"

  in /run/resolvconf/resolv.conf (link to by /etc/resolv.conf)

  With option present many dns lookups fail with both FF and chrome browswers and thunderbird...
  This is on a home network, with router set as dns proxy for external wan, not using NetworkManager

  Deleting the option on live system results in the issue immediately
  disappearing, but on reboot it is added back in (by systemd-resolve ?)

  I cannot find any option to prevent this being added, so presumably it
  is hard-coded in systemd following the update?

  systemd:
    Installed: 237-3ubuntu10.13

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