/etc/resolv.conf changes

[Roger Heflin]

Aaron Konstam wrote:
> On Mon, 2008-03-24 at 17:58 -0400, Matthew Saltzman wrote:
>> On Mon, 2008-03-24 at 16:09 -0600, Aaron Konstam wrote:
>>> On Mon, 2008-03-24 at 12:49 -0700, vincenzo romero wrote:
>>>> Hello all,
>>>>
>>>> I'm getting frustrated attempting to understand; I googled and asked
>>>> folks and am unable to get a straight answer.
>>>>
>>>> 1.  How is the /etc/resolv.conf file maintained ?  I do not seem to
>>>> get a consistent result when I save resolv.conf configuration from GUI
>>>> or by hand using vim /etc/resolv.conf.
>>>>
>>>> a.  Sometimes I the entries toggles between the two entries:
>>>>
>>>> # generated by NetworkManager, do not edit!
>>>> ; Use a local caching nameserver controlled by NetworkManager
>>>> nameserver 127.0.0.1
>>>>
>>>> b.  then when I restart the network services some the /etc/resolv.conf
>>>> file appears like this:
>>>> # generated by NetworkManager, do not edit!
>>>> ; Use a local caching nameserver controlled by NetworkManager
>>>> search lab.mycompany.com
>>>> nameserver 192.168.17.2
>>>>
>>>> This host is:
>>>>
>>>> - a DNS server that is authoritative for its domain within the
>>>> 192.168.16/20 network
>>>> - I believe that even as DNS server, this host should have its
>>>> resolv.conf file configured to define itself as a DNS server, right?
>>>>
>>>> I apologize for the naive questions, but I am a newbie and am unable
>>>> to gather a straightforward answer.
>>>>
>>>> thanks in advance.
>>> You really can't edit /etc/resolv.conf when you are using a DNS server.
>>> When you are connected to the network it is the DNS nameserver that sets
>>> up the resolv.conf file. In the first case above:
>> This isn't quite correct.  
>>
>> /etc/resolv.conf contains the IP addresses of your DNS servers.
> This is a semantic argument. We are talking about wireless. Until you
> connect to the wireless router's AP the resolve.conf computer has no
> idea about the name of your DNS server. The router supplies that form
> the DNS server.

If you semantic you mean wrong, yes.  The DNS server supplies *NOTHING*, the 
DHCP server supplies whatever setting it has for the DNS entry.

If you are using static ip and DNS servers you *MUST* edit your resolv.conf to 
point to the proper DNS server, so your original statement of "You really can't 
edit /etc/resolv.conf when you are using a DNS server." is just completely 
wrong.   Using a DNS server has nothing to do with whether you can edit the 
resolv.conf file or not, using a DHCP server does, as the dhcp client sets it 
based on what the DHCP server tells it, and if you edit the resolv.conf while 
using at DHCP server then you will have issues.

                           Roger