[gentoo-user] DNS lookup fails on a server; no changes since it worked

[gentoo-user] DNS lookup fails on a server; no changes since it worked

[Micah R Ledbetter]

I have a server out on the net, and it's been up for a week or two.  
I've been on and off it all week long, but as of last night, DNS  
didn't seem to work for it. Network connectivity worked, because not  
only could I ssh *in*, but I could also contact the outside network  
as long as I used something in the hosts file or an IP address.  
Adding more (known good) DNS servers to /etc/resolv.conf doesn't seem  
to help. DNS was working recently, and I haven't changed anything  
since then. A reboot didn't help (I would have just stopped &&  
started networking... but, well, all I have is ssh, so...).

One very weird thing is that it can apparently send mail to outside  
network addresses. It could send to my gmail account fine last night,  
though it seemed to take a while (20 minutes or so, when normally  
it's instantaneous). I don't have gmail or google in my /etc/hosts.

I've seen elsewhere to look at the output of iptables, but it has  
never been installed.
The contents of /etc/nsswitch.conf are at http://vlack.com/vlack/lol/ 
nsswitch.conf. I'm getting nowhere, and I have no idea why.

Thanks.

  - Micah
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Re: [gentoo-user] DNS lookup fails on a server; no changes since it worked

[A. Khattri]

On Sun, 20 Nov 2005, Micah R Ledbetter wrote:

> I have a server out on the net, and it's been up for a week or two.
> I've been on and off it all week long, but as of last night, DNS
> didn't seem to work for it. Network connectivity worked, because not
> only could I ssh *in*, but I could also contact the outside network
> as long as I used something in the hosts file or an IP address.
> Adding more (known good) DNS servers to /etc/resolv.conf doesn't seem
> to help. DNS was working recently, and I haven't changed anything
> since then. A reboot didn't help (I would have just stopped &&
> started networking... but, well, all I have is ssh, so...).
>
> One very weird thing is that it can apparently send mail to outside
> network addresses. It could send to my gmail account fine last night,
> though it seemed to take a while (20 minutes or so, when normally
> it's instantaneous). I don't have gmail or google in my /etc/hosts.
>
> I've seen elsewhere to look at the output of iptables, but it has
> never been installed.
> The contents of /etc/nsswitch.conf are at http://vlack.com/vlack/lol/
> nsswitch.conf. I'm getting nowhere, and I have no idea why.

What is /etc/resolv.conf?

Are you running a local name server or uses someone else's?

If you are using someone else's can you ping them?

If you can ping them, install bind-tools and see if you can run direct
queries against them with dig or host, something like:

dig @xxx.xxx.xxx.xxx -t mx gentoo.org

where xxx.xxx.xxx.xxx is the IP of the DNS server you are checking.

Lots of troubleshooting options here.



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