[CentOS] Slow login to system without internet connection

Tue Nov 20 20:57:11 UTC 2012
Les Mikesell <lesmikesell at gmail.com>

On Tue, Nov 20, 2012 at 2:45 PM, Ljubomir Ljubojevic <office at plnet.rs> wrote:
>> Most server apps will do a reverse-DNS lookup, if only to log the name
>> for the connection, some will try an ident query for the user at the
>> other end of the socket.   A 30+ second delay is a pretty sure sign
>> that one or more of the DNS servers in your resolv.conf did not
>> respond.  Running a local nameserver with a dummy local domain is one
>> way to fix it, but just putting all your local systems in the
>> /etc/hosts file will work too.
> OK, that is what crossed my mind, but what I was hopping for is some
> elegant solution that would decrease the timeout. My server already has
> DNS server running and "nameserver" as first in /etc/resolv.conf.

OK, but does it answer for your local network or do those queries
float up to the roots to get an answer?

> So the question is: "is there a setting that will reduce that DNS
> timeout for all running services, maybe like a ping-watchdog that would
> recognize the problem and skip the reverse-DNS lookup if DNS servers are
> not reachable?"

How about adding zone files for the things that belong to you?   I've
always been surprised that distributions that contain name servers
don't include dummy reverse zones for all the private  IP ranges.  It
must make a huge load on the DNS infrastructure when everyone passes
those queries upstream where they will always fail (but quickly...).
You'd get the same answer even faster if you had an empty zone file

   Les Mikesell
     lesmikesell at gmail.com