Name resolution with unqualified names

[Xen]

Kevin O'Gorman schreef op 27-11-2017 21:57:

On reflection, I am not satisfied with this approach.
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I understand


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On Camelot running Xubuntu and Plato running Ubuntu (both in desktop 
versions), /run/resolveconf/resolv.conf is:
     # Dynamic resolv.conf(5) file for glibc resolver(3) generated by 
resolvconf(8)
     #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE 
OVERWRITTEN
     nameserver 127.0.1.1
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Like other people say, this points to dnsmasq as employed by 
NetworkManager.

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On gog and magog, running Ubuntu server 127.0.1.1 is replaced by an IP 
that seems to be the router; at least pointing a browser at that IP gets 
me the internal support page from the router.

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This reveals that you are not running NetworkManager on the server.

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Other oddities:
   gog and magog can find each other using nslookup(1), which reports 
using the router as its server; neither one can find camelot or plato in 
that way unless i add the parameter to make them use the router.

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type "nmcli device show | grep DNS" on Camelot and Plato to see which 
DNS servers they have automatically configured"

gog and magog don't have each other in /etc/hosts? Just checking.

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Now on reflection (a day later) there is one ray of hope.  The the two 
that use the router for DNS are running Ubuntu server, and they are the 
ones that behave as I would prefer -- able to discover eachother by 
their unqualified names (I can't really give them qualified names 
anyway, because I only have one externally visible IP address, or can 
I?).

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Well there are two types of qualified names: private and internal to 
your network, or public.

If you did have a public domain then.... dnsmasq running on one of your 
servers could be configured as authorative for that public domain. That 
means your internal hosts would get external names as well.

So camelot.kevinogorman would start to exist on the internet.

I mean camelot.kevinogorman.com, for example.

If you only have a private domain, then "camelot.local" is a "qualified 
name" however this creates the issues we talked about in the other 
thread. So if you want to not have to deal with that, you would pick 
"camelot.l...", I mean "camelot.home" for instance, and that also is a 
qualified name.

Now I don't know WHY your servers resolve those names.

- Do they have fixed IPs?
- Do they have router-supplied fixed IPS because you gave them a 'static 
lease' ?

- Does the router supply a domain using DHCP?

- Do the servers have a "search" parameter in /etc/resolv.conf that 
mentions that domain?

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   I vaguely remember that the server install had a bunch of extras, most 
of which I declined.  I think one of them may have been a DNS server.  
Seeing no need, I declined.  Could it be that the desktop installs have 
a DNS server by default and that the installed DNS server is exposing 
127.0.1.1 and it is inferior to the router or needs further 
configuration?
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The desktops are running a stripped down version of "dnsmasq" controlled 
by NetworkManager.

"nmcli device show" and look for:

IP4.DOMAIN[1]:                          local

This domain is the domain that should be configured on your server.

On your router.

You must try to find if there is any "qualified" domain that is secretly 
getting used.