[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 127.0.0.1" 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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