[CentOS] Slow login to system without internet connection

Ljubomir Ljubojevic office at plnet.rs
Tue Nov 20 20:45:09 UTC 2012

On 11/20/2012 09:25 PM, Les Mikesell wrote:
> On Tue, Nov 20, 2012 at 12:48 PM, Ljubomir Ljubojevic <office at plnet.rs> wrote:
>> Now, when there was power failure (works on the transformer there), I
>> lost my internet connection, but router and wireless routers for the
>> rest of my towers were accessible. SSH logins to any of them is instant.
>> But when I tried to login to my server, it was not instantenous, and I
>> think it was 15+, maybe even 30+ seconds (I forgot to time it) from
>> start of ssh command to password prompt. It is in-house connection, so
>> there is nothing to traceroute.
> 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.

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?"

Adding and maintaining 30+ subnets in /etc/hosts is not really a good 
solution, and booting the server without reachable DNS server in some 
cases can be really frustrating, like if I boot Lap-top on the silo when 
internet connection is down (It was happening to me when I ran RHEL 6 
beta I think on each opening of the terminal, but I can not say I have 
seen this lately).


Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

Google is the Mother, Google is the Father, and traceroute is your
trusty Spiderman...
StarOS, Mikrotik and CentOS/RHEL/Linux consultant

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