How to keep dns-nameservers line in interfaces?

[zkvvoob]

Hi guys,

I'm running a server with Ubuntu 12.10. For some reason, however, the line

dns-nameservers 8.8.8.8 8.8.4.4

disappears from time to time which causes severe mayhem, including mail messages not being delivered, etc.

Could you tell me how to set up the DNS properly so that they stay in place no matter what?

Thanks a lot!

[papibe]

Hi zkvvoob.

Could you post the result of these commands?

apt-cache policy network-manager

cat /etc/network/interfaces 

apt-cache policy resolvconf 

cat /etc/resolv.conf

Regards.

[zkvvoob]

Certainly, papibe. Here are the results:

apt-cache policy network-manager
network-manager:
  Installed: (none)
  Candidate: 0.9.6.0-0ubuntu7
  Version table:
     0.9.6.0-0ubuntu7 0
        500 http://bg.archive.ubuntu.com/ubuntu/ quantal/main i386 Packages

cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).


# The loopback network interface
auto lo
iface lo inet loopback


# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.0.105
        netmask 255.255.255.0
        network 192.168.0.0
        broadcast 192.168.0.255
        gateway 192.168.0.1
        dns-nameservers 8.8.8.8 8.8.4.4

apt-cache policy resolvconf
resolvconf:
  Installed: 1.67ubuntu2
  Candidate: 1.67ubuntu2
  Version table:
 *** 1.67ubuntu2 0
        500 http://bg.archive.ubuntu.com/ubuntu/ quantal/main i386 Packages
        100 /var/lib/dpkg/status

cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8
nameserver 8.8.4.4

[papibe]

Thanks. Everything looks OK at first sight.

Is /etc/resolv.conf a link, isn't it? Could you post the result of this command?

ls -l /etc/resolv.conf

There seems to be no new line on the interfaces file. Could you post the result of this command?

od -a /etc/network/interfaces

Regards.

[zkvvoob]

Here you go:

ls -l /etc/resolv.conf
lrwxrwxrwx 1 root root 29 Apr  2 18:42 /etc/resolv.conf -> ../run/resolvconf/resolv.conf

od -a /etc/network/interfaces
0000000   #  sp   T   h   i   s  sp   f   i   l   e  sp   d   e   s   c
0000020   r   i   b   e   s  sp   t   h   e  sp   n   e   t   w   o   r
0000040   k  sp   i   n   t   e   r   f   a   c   e   s  sp   a   v   a
0000060   i   l   a   b   l   e  sp   o   n  sp   y   o   u   r  sp   s
0000100   y   s   t   e   m  nl   #  sp   a   n   d  sp   h   o   w  sp
0000120   t   o  sp   a   c   t   i   v   a   t   e  sp   t   h   e   m
0000140   .  sp   F   o   r  sp   m   o   r   e  sp   i   n   f   o   r
0000160   m   a   t   i   o   n   ,  sp   s   e   e  sp   i   n   t   e
0000200   r   f   a   c   e   s   (   5   )   .  nl  nl   #  sp   T   h
0000220   e  sp   l   o   o   p   b   a   c   k  sp   n   e   t   w   o
0000240   r   k  sp   i   n   t   e   r   f   a   c   e  nl   a   u   t
0000260   o  sp   l   o  nl   i   f   a   c   e  sp   l   o  sp   i   n
0000300   e   t  sp   l   o   o   p   b   a   c   k  nl  nl   #  sp   T
0000320   h   e  sp   p   r   i   m   a   r   y  sp   n   e   t   w   o
0000340   r   k  sp   i   n   t   e   r   f   a   c   e  nl   a   u   t
0000360   o  sp   e   t   h   0  nl   i   f   a   c   e  sp   e   t   h
0000400   0  sp   i   n   e   t  sp   s   t   a   t   i   c  nl  sp  sp
0000420  sp  sp  sp  sp  sp  sp   a   d   d   r   e   s   s  sp   1   9
0000440   2   .   1   6   8   .   0   .   1   0   5  nl  sp  sp  sp  sp
0000460  sp  sp  sp  sp   n   e   t   m   a   s   k  sp   2   5   5   .
0000500   2   5   5   .   2   5   5   .   0  nl  sp  sp  sp  sp  sp  sp
0000520  sp  sp   n   e   t   w   o   r   k  sp   1   9   2   .   1   6
0000540   8   .   0   .   0  nl  sp  sp  sp  sp  sp  sp  sp  sp   b   r
0000560   o   a   d   c   a   s   t  sp   1   9   2   .   1   6   8   .
0000600   0   .   2   5   5  nl  sp  sp  sp  sp  sp  sp  sp  sp   g   a
0000620   t   e   w   a   y  sp   1   9   2   .   1   6   8   .   0   .
0000640   1  nl  ht   d   n   s   -   n   a   m   e   s   e   r   v   e
0000660   r   s  sp   8   .   8   .   8   .   8  sp   8   .   8   .   4
0000700   .   4  nl
0000703

[papibe]

Everything looks fine.

The only think I can think of is that the dns line is indented using a tab instead of spaces, like the others. That shouldn't a problem though.

Is that line really disappearing from interfaces, or just the correct DNS not appearing on resolv.conf after boot?

If so, I would suspect the problem comes from the resolvconf package. In such a case, it could be valuable to reconfigure it:

sudo dpkg-reconfigure resolvconf

Let us know how it goes.
Regards.

[jdthood]

I'm running a server with Ubuntu 12.10. For some reason, however, the line

dns-nameservers 8.8.8.8 8.8.4.4

disappears from time to time which causes severe mayhem, including mail messages not being delivered, etc.

Could you tell me how to set up the DNS properly so that they stay in place no matter what?

Can you confirm that you mean that the "dns-nameservers" line disappears from /etc/network/interfaces? That would be *very* unusual.

[zkvvoob]

Hi guys,

During the initial configuration of the server, I explicitly made sure that the interfaces contained a setting for DNS. However, when I completed everything I went on to update and upgrade the installation, none of the repositories could be resolved. Then I checked the interfaces file again and the dns-nameservers line was simply empty. I added it and it all went on as normal.

Last night, however, when I was checking why emails were arriving but could not be sent, I thought I should check the interfaces file and again - that notorious line was not there.

Granted, I am new to Linux and I might have done a few things wrong, but one thing I am sure of and that is that I have personally set these DNSs numerous times.

Meanwhile, I'll keep a look whether this thing happens again and if it does, I'll go with papibe's suggesion.

Thanks a lot!