For a long time on Windows and OSX, Firefox has had combined search and address bar without recourse to any addon. I am running Ubuntu and the search and address bar is separate and I can't find any option to do this in the preferences and about:config. Do I have to use an addon ?
You can just remove the search box. The address bar should have the same behavior (auto-search).
If it does not, you can try changing the keyword.URL setting.
You need to install Foobar Firefox extension. It takes maximum 5 seconds and Firefox need to be restarted.
Foobar integrates the functionality of the search bar into the address bar. This not only streamlines Firefox's appearance, but also makes search and navigation quicker and easier than ever.