[CentOS] Slow DNS lookups on CentOS6

[John Hodrien]

On Tue, 27 Sep 2011, Alfred von Campe wrote:

> Most of my desktops are still running CentOS5, but I have installed CentOS6
> on a few of them.  The users on those desktops are reporting that DNS
> lookups are slow, and from my brief tests, that does appear to be the case.
> After some googling, I found a suggestion to disable IPv6, but that didn't
> help.  So I tried to figure out where the delay occurs using strace and
> ltrace, but that didn't help much.  When running ltrace, the process I'm
> trying to trace (host, nslookup) just dies.  And the output of strace does
> show a 3+ second delay, but I can't figure out what it's telling me:
>
> The CentOS5 systems on the same network with the same /etc/resolv.conf file
> do not have these delays.  Has anyone else seen this or have some
> suggestions as to how to debug this?

You probably want to do an strace -f host blah rather than a basic strace, or
I think you'll lose what's going on.

Are you running either sssd or nscd on your box?

I've done nothing special, and DNS seems fast enough.

jh