[CentOS] differences in DNS between boxes

Les Mikesell lesmikesell at gmail.com
Tue Aug 4 22:23:04 UTC 2009

Mike -- EMAIL IGNORED wrote:
> On Tue, 04 Aug 2009 21:31:22 +0200, Kai Schaetzl wrote:
>> Mike -- EMAIL IGNORED wrote on Tue, 4 Aug 2009 16:56:22 +0000 (UTC):
>>> Please refer to my thread "excessive DNS slows httpd"
>> Why don't you keep posting in there then?
> Because the new title reflects a new focus, and I hoped
> to attract different people.
>>> Suggestions would be most welcome.
>> Foremost, you want to find out why those queries are generated despite
>> the fact that hostnamelookups are off. That is surely something in your
>> configuration or a web application. It's not a general problem of Apache
>> on CentOS, mine are all not doing that.
>> Kai
> Until now, for a long time, mine wasn't doing it either.
> Part of the problem was suggested by someone on the Apache group;
> there are two problems:
> 1. Both boxes have nscd, but it was not running on the CentOS
>    box.  Now that I fixed that, all but the first connection
>    are rapid, as you might expect.
> 2. We still do not why the change in httpd.conf caused the
>    problem to appear.  However, my belief that there was a
>    difference between the two machines is accounted for
>    by the difference in /etc/init.d/nscd . When I tried it
>    for the first time this morning, the box that previously
>    been fast was slow.  No doubt, the nscd storage had
>    timed out.
> Except that nscd was not set to run, it is probably not
> specifically a CentOS problem.  Perhaps I made a wrong
> choice in setup?

If I really want to know what is different between two boxes, I'll do 
something like NFS mount one into the other or rsync their /etc trees 
somewhere on a common host and let diff -r walk through them.

Are you sure this isn't as simple as having (and using, check your 
resolv.conf) a caching name server running on one box so most lookups 
are resolved locally while the other is making the query to something slow?

   Les Mikesell
    lesmikesell at gmail.com

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