NetworkManager-resolv.conf -

[Ed Greshko]

On 11/16/2012 07:01 PM, Timothy Murphy wrote:
> Tim wrote:
>
>>> So, maybe NetworkManager should change the way it works? I'm not sure.
>> That's also difficult to answer.  For quite some time, it was clear that
>> it was only aimed at the GUI users, as there was only a GUI interface
>> for it.  Command line usage came later on.  It is supposedly possible to
>> do what people have been wanting to do, with the GUI, if only they
>> bothered trying to use it.  It's clear, from many of the discussions,
>> that they haven't.
> In my view, the action of NM in over-writing /etc/resolv.conf
> is completely illogical.
> There is no conceivable situation in which this might help.

Since you seem to be talking about wireless in the section below, it may make perfect sense.  When you connect to a wireless access point you most likely (unless you control the access point) would expect it to be running a DHCP server which will supply your IP address, the default gateway, and DNS settings.  It may very well be advantageous to use the DNS settings supplied by the access point since it should be supplying the address of a DNS server close by.  Additionally, depending on the network, DNS requests may be blocked to addresses outside the network.

>
> Also, in my experience NM does NOT get the DNS settings from the server.
>
> I run NM on my Fedora-17/KDE laptop.
> Normally this works fine - it has certainly improved greatly over the years.
> But if I go out of WiFi range then NM comments out the DNS entries 
> in /etc/resolv.conf .
> However, if I go back in range, it does not add the DNS entries
> from /etc/dhcp/dhcpd.conf on the server, where I have
>
>   # option definitions common to all supported networks...
>   option domain-name "gayleard.com";
>   option domain-name-servers 159.134.237.6,159.134.248.17;

I don't know what you mean by "from the server".  But, if in the case you cite above you mean your laptop is the server and it has info in /etc/dhcp/dhcpd.conf then I wouldn't expect its information added to your DNS settings either. 

Why?  DHCP is a networking protocol.  If you are in a wireless environment and have no network when you go out of range your settings get cleared out.  Since you have no network, you can't get the info from the "server".  Then, when you get back into range your system is communicating with the access point only until such time as you've authenticated and the IP addresses have been set up.  By that time your system will receive the settings and won't communicate with a second DHCP server.

>
> I'm not sure what you mean by "the GUI".
> If you mean Network Management Settings, I see nothing there
> that would allow me to alter the settings in /etc/resolv.conf .
>

Since, again, you are talking about a wireless situation the DNS settings are on a "per network" basis. 

If you click on the NM icon in the systray and then Manage Connections, you will be brought up to a dialog box with tabs and the various connections.  The wireless tab will have a list of connections for which you have configured authentication details.  If you edit one of those you will see under the IPv4 addresses tab entries labeled "Additional DNS servers" and "Additional Search Domains" where you can enter "static" entries.

My wireless access point gives out its IP address as a DNS server and then forwards DNS requests to servers that have been defined in its configuration.  Those servers are my ISPs servers.  I want it that way for any visitors.  But, for my own purposes I also want to use an internal DNS server so I place the IP address of it in "Additional DNS servers".  So, when I get in range my resolv.conf will read:

Generated by NetworkManager
search greshko.com
nameserver 192.168.0.1
nameserver 192.168.0.55

If I didn't make those entries as I've described it would simply read....

Generated by NetworkManager
nameserver 192.168.0.1


-- 
Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning. -- Rick Cook, The Wizardry Compiled