If you have the password, try logging on as root now. Enter the whoami command to verify your identity. Then _log out immediately_. When you’re root, the kernel will not protect you from yourself, because root has permission to do anything at all to the system. Don’t experiment while you’re root. In fact, don’t do anything as root unless absolutely necessary. This isn’t a matter of security, but rather of stability. Your system will run much better if it can keep you from making mistakes.
You may find the su command more convenient than logging in as root. su allows you to assume the identity of another user, usually root unless you specify someone else. (You can remember that su stands for Super User, though some say it stands for Set UserID.)
Here’s something to try. Log on as yourself—that is, not as root. Then your session will look something like the one in Figure 4.1.
[Illustration: Figure 4.1: Sample session with su]
When you’re doing system administration tasks, you should do as much as possible as yourself. Then use su, do the part that requires root privileges, and use the exit command to turn off privileges so you can no longer harm anything.
You can use su to assume the identity of any user on the system, not just root. To do this, type su _user_ where _user_ is the user you want to become. You’ll have to know the user’s password, of course, unless you’re root at the time or the user has no password.
The Linux kernel supports _virtual consoles_. These provide a way of making your single screen and keyboard seem like multiple terminals that are connected to the same system. Thankfully, using virtual consoles is one of the simplest things about Debian: There are “hot keys” for switching among the consoles quickly. To try it, log in to your system and press Alt-F2 (simultaneously press the left Alt key, and F2, that is, function key number 2).
You should find yourself at another login prompt. Don’t panic: You are now on virtual console (VC) number 2! Log in here and do some things—more whoami commands or whatever—to confirm that this is a real login shell. Now you can return to virtual console number 1 by pressing Alt-F1. Or you can move on to a _third_ virtual console, in the obvious way (Alt-F3).