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

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

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.

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 192.168.3.3
        network 192.168.3.0
        netmask 255.255.255.0
        broadcast 192.168.3.255
        gateway 192.168.3.1

auto br0
  iface br0 inet static
  address 192.168.3.3
  netmask 255.255.255.0
  network 192.168.3.0
  broadcast 192.168.3.255
  gateway 192.168.3.1
  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.

nameserver 192.168.3.1

Everything seems to be working again – no more NFS failures on bootup, and all network interface seem present and stable!