Why do the wireless connection details not appear in the interfaces file on Ubuntu 12.04 LTS

Question

I was perusing the interfaces file in the path /etc/network/ on a Ubuntu 12.04 LTS laptop that is connected to the wireless network and noticed that there are no entries. Why is that?

I am able to browse to websites, access emails, etc

Answer 1

That file is for an antiquated network configuration method which is deprecated (meaning that it is only used if you specifically disable its replacement and enable it).

The reason it was deprecated is that it's not very customizable or configurable. For instance, you can't supply WiFi passwords this way. You can't configure Bluetooth or VPN connections. You can't configure cellular broadband modems. You also can't change the configuration dynamically at runtime, and any graphical interface that attempts to adjust it at runtime is doomed to failure because of the wonky configuration file it uses.

The replacement is called NetworkManager. This is a piece of infrastructure (a daemon and some utilities and libraries) that allows individual applications, the desktop, and the hardware to interface together to manage and understand your network configuration. It does this way better than the old way used to.

To modify NetworkManager configuration from the console without a graphical user interface, check out the following manpages:

networkmanager.conf

nm-tool

nm-online

nmcli

The NetworkManager configuration data itself is stored in GConf or GSettings (depending on the version of NetworkManager). Note that GSettings is a Gnome 3.0 configuration database interface that provides various "backends", which may include GConf, or the "preferred default" as of Gnome 3.0, which is Dconf. The exact details depend on which version of NetworkManager and which Gnome packages you are using.

GConf data can be stored and retrieved from the console with gconftool-2 manpage here. GSettings data can be stored and retrieved from the console with the gsettings command manpage here.

Depending on the complexity of your configuration, it may be necessary to directly manipulate the GConf or GSettings data from the command line if nmcli doesn't provide enough functionality for you to get connected. I don't think it yet provides functionality for specifying a WPA2 passphrase, but if you knew enough about the GConf/GSettings data, you could set the key/values directly.

If you don't have the console package(s) already installed to access the required commands, and don't have internet access, your only real solution is to install the packages from external media -- a CD, floppy, flash drive, or similar.