Fluxbox is a stacking window manager for the X Window System, which started as a fork of Blackbox 0.61.1 in 2001, with the same aim to be lightweight. Its user interface has only a taskbar, a pop-up menu accessible by right-clicking on the desktop, and minimal support for graphical icons.
Below steps will show you how to install Fluxbox on Ubuntu 13.04 Raring.
1.) Press Ctrl+Alt+T to open a terminal window, run this command to install Fluxbox:
sudo apt-get install -y fluxbox
2.) That’s it! Once installed, log out. Click the gear button and select Fluxbox.