[Bug 1821491] Re: DNS lookup fails for local hosts

[Dan Streetman]

> So it seems to me that lookups by systemd-resolved
> are failing to lookup the hostname on the local DNS
> (even if this is by design)

yes, this is by design.  systemd-resolved never forwards "single label"
addresses to upstream nameservers.

> If the router has the hostname AND domainname defined:
> phspi05 192.168.2.35
> phspi05.phs 192.168.2.35

you don't need the router configured to resolve the "single label"
(without .phs) hostname (unless your router doesn't have 'phs' in its
resolv.conf search list, and you need to look up the hostname from the
router itself).

> on laptop
> dig phspi05 = fails

stop using dig to debug your system.  the behavior above is correct (dig
*should* fail when querying the local systemd-resolved resolver without
using .phs domain suffix).  Instead try using a program that uses
getaddrinfo(), like nslookup, ping, or even host.  e.g.:

$ host phspi05

> I guess I have a workaround to manually edit resolv.conf, and as I don't
> reboot that often it is not a big issue, but it doesn't feel right somehow.

it isn't right, and you don't need to.  Just make sure your router
delivers your domain as part of its dhcp reply, and you will be fine.
Your resolv.conf will contain your local domain in its 'search' and all
programs on your system using getaddrinfo() and friends will correctly
look up any address with your domain appended.

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https://bugs.launchpad.net/bugs/1821491

Title:
  DNS lookup fails for local hosts

Status in systemd package in Ubuntu:
  Invalid

Bug description:
  Mint 19 (Ubuntu Bionic) 
  Laptop so Using NetworkManager, and connecting wirelessly to LAN
  Upgraded from Mint 18.3 so using resolvconf...

  Versions:
  network-manager: 1.10.6-2ubuntu1.1
  resolvconf: 1.79ubuntu10.18.04.3 or 1.79ubuntu10.18.04.2
  systemd: 237-3ubuntu10.15

  dns is specified in NetworkMananager as 192.168.2.1
  the dns is a router, and has static ips assigned to certain hosts on my lan...

  $cat resolv.conf
  nameserver 127.0.0.53
  search phs
  options edns0

  $ nslookup phspi05
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  ** server can't find phspi05: SERVFAIL

  If I explicity specify the dns:

  $ nslookup phspi05 192.168.2.1
  Server:		192.168.2.1
  Address:	192.168.2.1#53

  Non-authoritative answer:
  Name:	phspi05
  Address: 192.168.2.35

  I get the correct ip address...

  Same with dig...

  I would expect that the nameserver set in network-manager would be
  used....

  From tail of $ systemd-resolve --status

  Link 2 (wlp2s0)
        Current Scopes: DNS
         LLMNR setting: yes
  MulticastDNS setting: no
        DNSSEC setting: no
      DNSSEC supported: no
           DNS Servers: 192.168.2.1
            DNS Domain: phs

  So the dns address had been picked up from NetworkManager, but
  apparently is not being used...

  Thought it might be related to this bug:
  https://bugs.launchpad.net/ubuntu/bionic/+source/resolvconf/+bug/1817903

  So installed the proposed fix, but no change. I also tried removing
  package resolvconf, again no change...

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