Robert Penz wrote:
> I think you misunderstand me. dns using is ok, but it should use also hosts
> entries for A and PTR records, specially for its own hostname. To be
> specific I don't care about anything else accept its own hostname. Why does
> every Linux system have a /etc/hosts? because of the entry for loopback and
> its own hostname. If you use "ping" or any other program it checks the
> hosts file before it does a dns query.
> 

I understand your wish, but there are some technical difficulties to
fulfill it.

There are two sets of functions for name resolution:
  (a) gethostbyname(3) / getnameinfo(3) & Co
  (b) res_query(3) & Co

(a) is simpler to use, takes info account nsswitch.conf and asks all the
name services that are configured there -- /etc/hosts, ldap, DNS, etc --
in order they are configured there. But they allow just simple
questions: I have host name, what is IP address (and vice versa).

(b) only asks DNS, but allows to ask more complex questions, like what
is MX record for name example.com.

ping, telnet and "any other program" have luxury to use (a) set of
functions. Therefore, they "consult" /etc/hosts file. Courier, and any
other MTA, have to find MX records for other mail servers, TXT records
for SPF, and therefore they have to go for (b) set of functions. Code
using these functions is already complex. You ask to complicate it
further. Using two sets of resolving functions would complicate even more.

All problems, what could be solved by "consulting /etc/hosts", could be
solved by configuring DNS servers. And it is you, who is guilty for
putting all the eggs into single basket, and as consequence loosing DNS
service.

I have not checked other MTAs, if they check /etc/hosts, but I would bet
they don't. Most of single threaded IRC servers do not check /etc/hosts
too. The reason -- everything is doable using DNS. And DNS service
absolutely MUST WORK.

-- 
Aidas Kasparas
IT administrator
GM Consult Group, UAB

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