DNS caching nameserver problem

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

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?

Dar=EDo

On 5/30/05, gerardo juarez-mondragon =
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).
>=20
> 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.
>=20
> 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.
>=20
> What do you think is the problem?
> Is there a workaround?
>=20
> Thank you for your comments.
> Gerardo
>=20
>=20
>=20
> Searching for the best free email? Try MetaCrawler Mail, from the #1=
metasearch service on the Web, http://www.metacrawler.com
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin=
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Re: Re: DNS caching nameserver problem

Red Hat 7.something...



---- Begin Original Message ----

=46rom: Dar=EDo Mariani
Sent: Mon, 30 May 2005 15:24:04 -0300
To: gerardo juarez-mondragon

CC: linux-admin@vger.kernel.org
Subject: Re: DNS caching nameserver problem


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?

Dar=EDo

On 5/30/05, gerardo juarez-mondragon
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).
>=20
> 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.
>=20
> 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.
>=20
> What do you think is the problem?
> Is there a workaround?
>=20
> Thank you for your comments.
> Gerardo
>=20
>=20
>=20
> Searching for the best free email? Try
MetaCrawler Mail, from the #1 metasearch service
on the Web, http://www.metacrawler.com
> -
> To unsubscribe from this list: send the line
"unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at
http://vger.kernel.org/majordomo-info.html
>

---- End Original Message ----



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Re: DNS caching nameserver problem

>> 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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Re: Re: DNS caching nameserver problem

I did not check how does RedHat work but it has a script called
dhclient. Most probably you can add an option to
/etc/sysconfig/network or /etc/sysconfig/network-scripts/ifcfg-*. You
should better go to the redhat page and check its documentation.

Dar=EDo

On 5/30/05, gerardo juarez-mondragon =
wrote:
>=20
> Red Hat 7.something...
>=20
>=20
>=20
> ---- Begin Original Message ----
>=20
> From: Dar=EDo Mariani
> Sent: Mon, 30 May 2005 15:24:04 -0300
> To: gerardo juarez-mondragon
>
> CC: linux-admin@vger.kernel.org
> Subject: Re: DNS caching nameserver problem
>=20
>=20
> 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?
>=20
> Dar=EDo
>=20
> On 5/30/05, gerardo juarez-mondragon
> 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
> >
> >
> >
> > Searching for the best free email? Try
> MetaCrawler Mail, from the #1 metasearch service
> on the Web, http://www.metacrawler.com
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> "unsubscribe linux-admin" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at
> http://vger.kernel.org/majordomo-info.html
> >
>=20
> ---- End Original Message ----
>=20
>=20
>=20
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Re: Re: Re: DNS caching nameserver problem

Thanks Andrew and Dario, the problem is solved:

In /etc/sysconfig/network-scripts, there are 2
links 'ifup' and ifdown. Editing ifup, there is a
line specifying the options for pump. Adding the
no-dns option there does the trick. This is a
snippet of the ifup file, with the option added:

if [ -n "${DYNCONFIG}" ]; then
PUMPARGS="--no-dns"
DHCPCDARGS=



Gerardo




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