DNS caching nameserver problem

DNS caching nameserver problem

[gerardo juarez-mondragon]

I have a DNS caching server that works ok until
it is rebooted. When this happens it restarts
normally, except the /etc/resolv.conf file is
altered and the server stops serving names. (The
line 'nameserver 127.0.0.1' is missing and other
namservers appear instead).

The server obtains an address through DHCP and my
theory is that the DHCP server is providing it
with DNS servers as well, which it substitutes
when it probably shouldn't.

I have tried a horrible patch in rc.local,
stopping named, overwriting resolv.conf with a
correct copy and restarting, but
editing the file and restarting 'named' does not
seem to work 100% of the time, requiring
sometimes one or two restarts of the service to
make it serve names for the internal hosts.

What do you think is the problem?
Is there a workaround?

Thank you for your comments.
Gerardo



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Re: DNS caching nameserver problem

[Darío Mariani]

  Yes, the problem is that your DHCP client is overwriting the
resolv.conf file. How to avoid this, as far as I know, is
distribuition specific. What distribution do you have?

         Darío

On 5/30/05, gerardo juarez-mondragon <gjuarezmondragon@metacrawler.com> wrote:
> I have a DNS caching server that works ok until
> it is rebooted. When this happens it restarts
> normally, except the /etc/resolv.conf file is
> altered and the server stops serving names. (The
> line 'nameserver 127.0.0.1' is missing and other
> namservers appear instead).
> 
> The server obtains an address through DHCP and my
> theory is that the DHCP server is providing it
> with DNS servers as well, which it substitutes
> when it probably shouldn't.
> 
> I have tried a horrible patch in rc.local,
> stopping named, overwriting resolv.conf with a
> correct copy and restarting, but
> editing the file and restarting 'named' does not
> seem to work 100% of the time, requiring
> sometimes one or two restarts of the service to
> make it serve names for the internal hosts.
> 
> What do you think is the problem?
> Is there a workaround?
> 
> Thank you for your comments.
> Gerardo
> 
> 
> 
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Re: DNS caching nameserver problem

[Andrew Schulman]

>> I have a DNS caching server that works ok until
>> it is rebooted. When this happens it restarts
>> normally, except the /etc/resolv.conf file is
>> altered and the server stops serving names. (The
>> line 'nameserver 127.0.0.1' is missing and other
>> namservers appear instead).
>> 
>> The server obtains an address through DHCP and my
>> theory is that the DHCP server is providing it
>> with DNS servers as well, which it substitutes
>> when it probably shouldn't.
>> 
>> I have tried a horrible patch in rc.local,
>> stopping named, overwriting resolv.conf with a
>> correct copy and restarting, but
>> editing the file and restarting 'named' does not
>> seem to work 100% of the time, requiring
>> sometimes one or two restarts of the service to
>> make it serve names for the internal hosts.
>> 
>> What do you think is the problem?
>> Is there a workaround?
> 
>   Yes, the problem is that your DHCP client is overwriting the
> resolv.conf file. How to avoid this, as far as I know, is
> distribuition specific. What distribution do you have?

pump, for example, includes an option --no-dns that tells it not to
overwrite /etc/resolv.conf.  I use this along with my cacheing DNS server. 
I put 'nameserver 127.0.0.1' into /etc/resolv.conf, then I have pump run a
postprocessing script that extracts the DNS server information and writes
it to /etc/dnsmasq.conf, where dnsmasq (my cacheing name server) looks to
find the upstream DNS servers.

Good luck,
Andrew.


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