[Dnsmasq-discuss] Questions about /etc/hosts

[Geert Stappers]

On Fri, Feb 11, 2022 at 12:24:27AM +0100, Petr Menšík wrote:
> On 2/10/22 20:24, Chris Green wrote:
> > When running dnsmasq it (by default) uses /etc/hosts to provide some
> > system's addresses.
> >
> > Some of my systems have their names in the /etc/hosts file against
> > a loopback address so host t470 has:-
> >
> >     127.0.0.1   localhost
> >     127.0.1.1   t470.zbmc.eu t470
> >
> >
> > While others only have their names against their (static) IP address
> > so host backup has:-
> >
> >     192.168.1.1     2860n                   # Draytek router, internet
> >     192.168.1.2     dns.zbmc.eu dns         # this Pi running dnsmasq
> >     192.168.1.3     esprimo zbmc.eu         # my desktop system
> >     192.168.1.4     backup.zbmc.eu backup   # backup Raspberry Pi, also DNS/DHCP backup
> >
> >
> > Is that 127.0.1.1 loopback address just so that there is an IP for a
> > system to refer to itself (particularly in the case where it has DHCP
> > assigned IP so there isn't a fixed address for itself)?
> >
> >
> > Where a system has a static/fixed IP is it OK to have only the
> > 'localhost' loopback address and the 'real' static IP for 'self'?
> > E.g. can one have:-
> >
> >     127.0.0.1   localhost
> >
> >     192.168.1.1     2860n                   # Draytek router, internet
> >     192.168.1.2     dns.zbmc.eu dns         # this Pi running dnsmasq
> >     192.168.1.3     esprimo zbmc.eu         # my desktop system
} }     192.168.1.3     esprimo.zbmc.eu         # my desktop system
> >     192.168.1.4     backup.zbmc.eu backup   # backup Raspberry Pi, also DNS/DHCP backup
> >
> > As the /etc/hosts file on all of those systems (which have static IP)?
> >
> I think we would need to know, which distribution and version you are
> running.

And which computer of them is running dnsmasq as Domain Name Server
for the other computers.

> /etc/hosts is not directly controlled by dnsmasq.

dnsmasq, as DNServer,  uses /etc/hosts as source
for hostname-IPaddress-mapping. Consider it as source of a single thruth.

Back to
> > As the /etc/hosts file on all of those systems (which have static IP)?

That is fairly ignorant.  The whole idea of DNS is eliminating the
maintainance of /etc/hosts files.  And having hostname-IPaddress-mapping
in several places (/etc/hosts and DNS) creates several thruths, which
should be avoided.

 
> Depends on how t470 and t470.zbmc.eu names are used any by what
> services. I would recommend --local=/zbmc.eu/ or better auth-zone=zbmc.eu.

 
> I doubt host 127.0.1.1 were added automatically. Unless you don't know
> what does use it, I would recommend to comment it out and reboot.

???   (pronounance as "WTF")


> Unless you see any visible failures or delays during boot,
> it is safe to be removed :)

That :)  should be pronounanced as "it remains your decission"



Desktop esprimo has hostname esprimo.
Most likely is esprimo a DHCP client.
Esprimo could be (re)booted when there is no DNS and no DHCP server.

Upon boot will ask some services what is the address of esprimo.
Waiting for the absent DNS implies waiting for time-outs.
Having
  127.0.1.1     esprimo
in /etc/hosts will provide an answer to "What is the address of esprimo?"



Groeten
Geert Stappers
-- 
Silence is hard to parse