I recently switched by ubuntu 8.10 server/desktop to using the NetworkManger applet that comes as part of ubuntu. By default it was sat that; but wouldn’t let me change or adjust any of my network settings.
I discovered that in order to make it work I needed to modify the /etc/NetworkManager/nm-system-settings.conf.
david@george:~$ sudo nano /etc/NetworkManager/nm-system-settings.conf
Then change the managed=false line to managed=true
However, once I did this every time that I booted the machine it always come up using DHCP, and not using the static IP address that I had originally set. I discovered that I could always manually change the interface using the NetworkManager to use the static IP opposed to dynamic; but that was a manual task and not great for a machine that is supposed to be acting as a server.
I also noticed that the NFS Server failed to load at boot as well whilst I was using the NetworkManager.
So – today I decided to go back to manual network configuration as it seemed more stable than using the GUI! But that was not as straight forward as I hoped.
Firstly, I reverted back the line in /etc/NetworkManager/nm-system-settings.conf to say false. Secondly I quickly sorted out my /etc/networks/interfaces file so that it was correct.
iface lo inet loopback
iface eth0 inet static
iface br0 inet static
bridge_ports eth0 vbox0 vbox1
Note: I use VirtualBox for virtualisation; hence the need to the Bridge and the vbox references.
All seemed fine – IP traffic was all looking fine; but then I discovered that DNS lookups were not working. After a bit of routing around I noticed that NetworkManager also overwrites the /etc/resolv.conf file – and in my case that was pointing to a invalid entry. So I revert back my /etc/resolv.conf to something more sensible.
Everything seems to be working again – no more NFS failures on bootup, and all network interface seem present and stable!