Fixing DHCP Network Interface with Network Manager in Xubuntu 14.04 (Trusty Tahr)

A very annoying problem came back to a Xubuntu 14.04 (Trusty Tahr) system quite suddenly and annoyingly would not go away. This system would not obtain a DHCP address. The Network Manager tray icon was not even the "spinning" icon indicating it was trying to obtain an address from the DHCP server. I checked around the Internet for suggestions how to resolve this issue. Nothing we located and tested resolved the issue.

Years ago, last time I had a Xubuntu 14.04 pull this nonsense on me, booting off the Xubuntu 14.04 LiveCD was able to get an IP address from the DHCP server, and booting from the hard drive was then mysteriously successful. This time it would not be solved that easily.

Eventually I thought to purge off the Network Manager packages and to reinstall them. That solved the issues for us this time. So, my suggestion to add to the others to be found around the Internet is as follows:

On the system having the DHCP issue, run the following commands to investigate how many packages are involved with the Network Manager configuration on the system:

$ dpkg -l|grep network-manager
ii network-manager amd64 network management framework (daemon and userspace tools)
ii network-manager-gnome amd64 network management framework (GNOME frontend)
ii network-manager-pptp amd64 network management framework (PPTP plugin core)
ii network-manager-pptp-gnome amd64 network management framework (PPTP plugin GNOME GUI)
$ dpkg -l|grep libnm
ii libnm-glib-vpn1 amd64 network management framework (GLib VPN shared library)
ii libnm-glib4 amd64 network management framework (GLib shared library)
ii libnm-gtk-common all network management framework (common files for wifi and mobile)
ii libnm-gtk0 amd64 network management framework (GNOME dialogs for wifi and mobile)
ii libnm-util2 amd64 network management framework (shared library)

Note: I bolded the package names to be purged / reinstalled.

Then on a working Xubuntu 14.04 system, I reinstalled these packages to end up with them in my /var/cache/apt/archives/ directory. I then copied those packages via USB Stick to the system which was not obtaining a DHCP address.

Then on the affected system, in the USB Stick directory, I issued the following commands:

$ sudo dpkg -P network-manager network-manager-gnome network-manager-pptp network-manager-pptp-gnome libnm-glib-vpn1 libnm-glib4 libnm-gtk-common libnm-gtk0 libnm-util2
$ sudo dpkg -i *.deb

And after an IPL, the system THEN picked up an IP address from the DHCP server.

I hope this suggestion assisted someone.