[Bug 1624320] Re: systemd-resolved appends 127.0.0.53 to resolv.conf alongside existing entries

[Alroger Filho]

Same problem here. Editing resolv.conf or #8 post solves it.

I almost lost a RAID today because postfix was not able to send mdadm notifications - 
delivery temporarily suspended: Host or domain name not found. Name service error for name=smtp.gmail.com type=MX: Host not found

I use /etc/network/interfaces, nothing in networkmanager.
This is serious. Ubuntu shouldn't just start changing things like this, specially if it breaks a server.

Using a clean 17.04 install here.

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Title:
  systemd-resolved appends 127.0.0.53 to resolv.conf alongside existing
  entries

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  systemd-resolved, or more precisely the hook script
  /lib/systemd/system/systemd-resolved.service.d/resolvconf.conf, causes
  resolvconf to add 127.0.0.53 to the set of nameservers in
  /etc/resolv.conf alongside the other nameservers.  That makes no sense
  because systemd-resolved sets up 127.0.0.53 as a proxy for those other
  nameservers.  The effect is similar to bug 1624071 but for
  applications doing their own DNS lookups.  It breaks any DNSSEC
  validation that systemd-resolved tries to do; applications will
  failover to the other nameservers, bypassing validation failures.  And
  it makes failing queries take twice as long.

  /etc/resolv.conf should have only 127.0.0.53 when systemd-resolved is
  active.

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