i3 is a tiling window manager used in the EPITA computer rooms. It works very differently from the desktop environments you may be used to (Windows, macOS).

In a traditional desktop, windows float freely and you drag them around with the mouse. In i3, windows are automatically arranged to fill the screen without overlapping. Open one window and it takes up the entire screen. Open a second and the screen splits in two. Open a third and it splits again. Every pixel of screen space is used.

Everything in i3 is driven by the keyboard. There is no taskbar, no desktop icons, and no start menu to click. This feels disorienting at first. The learning curve is real. But the payoff is significant: once the shortcuts are in your fingers, you spend far less time fiddling with windows and can focus entirely on your work.

Opening a terminal#

Press Mod + Enter to open a terminal. The Mod key is the Windows key on school keyboards.

The terminal will be your main tool for the year. Get comfortable with it early.

Launching software with dmenu#

Press Mod + D to open dmenu — a launcher bar that appears at the top of the screen. Type the name of any program and press Enter to launch it.

Your first task: you are probably reading this guide on your phone. Open Firefox on the school computer by pressing Mod + D, typing firefox, and pressing Enter. Then navigate to this guide in Firefox so you can continue reading it on the screen in front of you.

Workspaces#

i3 organizes windows into numbered workspaces (1 through 10). Think of them as virtual screens: you switch between them instantly rather than minimizing and maximizing windows.

A common setup: a browser showing the subject or documentation side by side with your editor on workspace 1, and a terminal on workspace 2.

Closing a window#

Press Mod + Shift + Q to close the focused window.

Locking your session#

Whenever you leave the keyboard — even for a minute — lock your screen immediately. Press Mod + D, type i3lock, and press Enter.

For longer absences (going to lunch, heading to class, end of the day), locking is not enough: log out of your session entirely. Leaving a session open for hours occupies the machine for no reason, blocks it from other students who may need it, and is considered computer squatting. Log out out of respect for everyone sharing the room.

You are responsible for everything that happens in your session. If someone copies your code because you left your screen unlocked, you will be treated exactly the same as a student who deliberately shared their code. There is no exception.

Quick reference#