The Network Manager default for the Ubuntu distribution of Linux operating systems provides internet connectivity. The Network Manager cannot save a fixed IP address on Ubuntu Linux and the settings are lost when the system is rebooted. To have a static IP address on Ubuntu Linux ,the Network Manager must be uninstalled before the network interfaces are configured manually. The network interfaces can be configured to have a static IP in Ubuntu Linux by editing the interfaces file to include the fixed IP address . The configuration would be retained even after the Linux system has been restarted. NetworkManager is a program in Ubuntu 8.10, which aims to provide a simplified Internet connection. NetworkManager finds and maintains an internet connection at all costs. However it can cause a problem if you want to use a fixed IP address. Settings made in NetworkManager will not be applicable at the next restart. Ultimately if you assign a fixed IP address in NetworkManager, this setting will be forgotten the next time you reboot. A straightforward approach is to uninstall NetworkManager:
to validate the changes.