Beware - NetworkManager

[Matthew Saltzman]

On Mon, 11 Dec 2006, Marc Schwartz wrote:

> On Mon, 2006-12-11 at 12:12 -0500, Matthew Saltzman wrote:
>> On Mon, 11 Dec 2006, Marc Schwartz wrote:
>>
>>> Aaron Konstam wrote:
>>>> On Mon, 2006-12-11 at 09:42 -0500, Gene Poole wrote:
>>>>> Beware - It seems that the first time you use NetworkManager it destroys
>>>>> the contents of you resolv.conf (built at install time).  It also seems
>>>>> that it doesn't make a backup copy first.
>>>>>
>>>>> Thanks,
>>>>> Gene Poole
>>>>>
>>>> I have never noticed that this is true. I will have to look into your
>>>> statement.
>>>
>>> If you have a network profile that is based upon a fixed IP address and DNS
>>> servers (which I do have at home behind a router with DHCP disabled), then NM
>>> will overwrite the configurations for that profile, including
>>> /etc/resolv.conf.
>>>
>>> I use NM at work, where we have DHCP and of course with wireless networks
>>> when travelling.
>>>
>>> However, at home, I end up disabling NM and then run a shell script which
>>> activates the Home profile and associated config settings and then ifup's
>>> eth0.
>>>
>>> It seems to me that I have seen references to this previously, relative to
>>> using NM when one has a fixed IP and DNS settings. My recollection is that NM
>>> is really configured for DHCP based nets and does not (yet) support network
>>> profiles.
>>>
>>> However, I would love for somebody to tell me that I am wrong on this, as I
>>> would love to not have to go through the steps that I do when at home.
>>
>> Do you access the Internet directly at home or through some sort of
>> router?  If the latter, you can probably configure your home router to
>> provide DHCP service (including nameserver info) to your laptop.
>
> Matthew,
>
> As I note above, yes, I do use a router... :-)

Oh, yeah.  I see now.

>
> I have DHCP disabled as part of a multi-layer approach to security.
> Specific IPs are enabled for use by my family, all others are disabled.
>
> I suppose that I could still do this, as you note below, while enabling
> DHCP and DNS info and thus still use NM. I just had not taken that
> approach and NM has not been an issue until the last couple of FC
> releases anyway. I have been using RH/FC since the late RH 8.0 betas.

I don't think you have much to fear from DHCP on the wired side.  on the 
wireless side, I use MAC address restrictions on the WAP and DHCP and 
encryption for security.

>
>> I do this, and NM works just fine.  I actually use a Linux box as a home
>> server.  It runs dhcpd so it can even match IP addresses to MAC addresses
>> so machines get "static" addresses.
>>
>> IIRC, NM should respect a static id set in /etc/sysconfig/network-scripts,
>> but you still need to stop it and change profiles if you sometimes have a
>> static id and sometimes want to DHCP.
>
> Yeah, I do have the occasion where I need to go back and forth between
> fixed IP and DHCP, hence I wrote the scripts that I have to address
> this. As I note, a more unified approach via NM would be helpful.
>
> Having had the chance now to set up network connections with Windows,
> Linux and more recently, Mac OS X, the latter seems to have a relatively
> easy to use interface relative to selecting a "location" and enabling it
> along with the attendant profile.  My daughter's new Intel Core 2 Duo
> based MacBook, has this and it has made it very easy for her to go
> between home, university and other locations with a simple menu based
> selection, using location profiles that I configured for her. It is a
> lot easier than, for example, using the the gnome-netstatus-applet after
> disabling NM.
>
> In either case, it is a livable situation until such time as NM can
> support profiles.  Users in this situation just need to be aware of the
> gotchas.

IIRC, that's slated for a future release.

>
> Thanks,
>
> Marc
>
>
>
>

-- 
 		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs