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

[Steve Langasek]

Anders, are you still seeing this issue with currently-supported
versions of Ubuntu?  I have argued elsewhere that the correct thing to
do for 18.04 is to forcibly remove resolvconf on upgrades, switching
/etc/resolv.conf to exclusively point to /run/systemd/resolve/stub-
resolv.conf.  In the common case, however, this should not make a
difference.  What other sources of DNS settings do you have that are
feeding directly to resolvconf instead of resolved in 16.10 and later?

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

Status in systemd package in Ubuntu:
  Confirmed

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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