A very strange DNS problem

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blessme
Posts: 3
Joined: 2011/08/24 15:04:50

A very strange DNS problem

Post by blessme » 2011/08/24 15:11:04

This is a very strange problem. Very inconsistent in my opinion.

- I can ping any servers on my network via IP address.
- I can do 'nslookup' for any sites on the Internet. nslookup returns a correct IP address.
- Firefox can access Mozilla web site only. I can use IP address to access other websites, but I can't use DNS name.
- I turned off firewall services. It did not make any difference.

Seems like DNS gets blocked for some reason. But if it was really blocked, I should not do "nslookup' thing.

There is no hardware problem. The network card is working good. I did not have this issue with Centos 5.X. Seems like there is some sort of network blocking software running, but I can't figure that out.

jkhord
Posts: 29
Joined: 2010/03/10 23:54:45
Location: Washington, DC

Re: A very strange DNS problem

Post by jkhord » 2011/08/24 15:57:10

I've seen this behavior when SELINUX doesn't like something about /etc/resolv.conf

Did you, perhaps, copy an old version back to this host? Or symlink it to another file elsewhere on the system?


You may need to perform a relabel of your system -- to do this, you create an empty file called /.autorelabel and reboot. This process can take a long time, especially if you have a lot of local storage.

blessme
Posts: 3
Joined: 2011/08/24 15:04:50

Re: A very strange DNS problem

Post by blessme » 2011/08/24 16:12:54

[quote]
jkhord wrote:
I've seen this behavior when SELINUX doesn't like something about /etc/resolv.conf

Did you, perhaps, copy an old version back to this host? Or symlink it to another file elsewhere on the system?


You may need to perform a relabel of your system -- to do this, you create an empty file called /.autorelabel and reboot. This process can take a long time, especially if you have a lot of local storage.[/quote]


I did not copy the old version. The resolv.conf was created during the install.

Is "relabel" related to SELINUX?

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TrevorH
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Re: A very strange DNS problem

Post by TrevorH » 2011/08/24 16:22:11

Do an

[code]
ls -laZ /etc/resolv.conf
[/code]

and see what the SELinux context is now. It should be system_u:object_r:net_conf_t

blessme
Posts: 3
Joined: 2011/08/24 15:04:50

Re: A very strange DNS problem

Post by blessme » 2011/08/24 23:27:53

[quote]
TrevorH wrote:
Do an

[code]
ls -laZ /etc/resolv.conf
[/code]

and see what the SELinux context is now. It should be system_u:object_r:net_conf_t[/quote]

I did it. The file has the same permission.

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AlanBartlett
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A very strange DNS problem

Post by AlanBartlett » 2011/08/25 00:17:52

[quote]
I did it. The file has the same permission.
[/quote]
No. Not the file permissions but the file SELinux context. They are totally different entities.

Please post, for [b]Trevor[/b] to see, the output returned by --

[code]
[b]ls -laZ /etc/resolv.conf[/b]
[/code]

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