There are several methods you can use to get a shell while running an installation. On most systems, and if you are not installing over serial console, the easiest method is to switch to the second virtual console by pressing Left Alt F2 That is: press the Alt key on the left-hand side of the space bar and the F2 function key at the same time. (on a Mac keyboard, Option F2). Use Left Alt F1 to switch back to installer itself. If you cannot switch consoles, there is also an Execute a Shell item on the main menu that can be used to start a shell. To get back to the installer itself, type exit to close the shell. At this point you are booted from the RAM disk, and there is a limited set of Unix utilities available for your use. You can see what programs are available with the command ls /bin /sbin /usr/bin /usr/sbin and by typing help. The shell is a Bourne shell clone called ash and has some nice features like autocompletion and history. To edit and view files, use the text editor nano. Log files for the installation system can be found in the /var/log directory. Although you can do basically anything in a shell that the available commands allow you to do, the option to use a shell is really only there in case something goes wrong and for debugging. Doing things manually from the shell may interfere with the installation process and result in errors or an incomplete installation. In particular, you should always use let the installer activate your swap partition and not do this yourself from a shell.