So far, user elliot has been able to do quite a few things on the system. However, there are a whole lot of things that user elliot can't do! To demonstrate, let's try to create a file named happy in the /var directory:

elliot@ubuntu-linux:~$ touch /var/happy
touch: cannot touch '/var/happy': Permission denied

Oops! We got a Permission denied error.

Now let's try to create a new directory named games in /etc:

elliot@ubuntu-linux:/$ mkdir /etc/games
mkdir: cannot create directory ‘/etc/games': Permission denied

Again! We are getting the same error, Permission denied!

So what's going on here? Well, the user elliot doesn't have permission to do whatever he wants on the system! So who then? Who has permission to do anything on the system? It's the root user.

Accessing the root user

You can run the sudo -i command to access the root user for the first time on your system:

elliot@ubuntu-linux:~$ sudo -i
[sudo] password for elliot:
root@ubuntu-linux:~#

You will be prompted to enter your password, and then, all of a sudden, you have got superpowers!

Notice how the command prompt changed instead of a dollar sign ($), it now shows a # to greet the root user.

Let's run the whoami command to make sure that we are now logged in as the root user:

root@ubuntu-linux:~# whoami 
root

Awesome! Now let's display the current working directory:

root@ubuntu-linux:~# pwd
/root

Remember earlier that I told you that the home directory for the root user is /root and not under /home.

Figure 1: /root is the home directory for the root user

Now let's rerun both commands that we got permission denied for, but this time, we run both commands as the root user.

root@ubuntu-linux:~# touch /var/happy 
root@ubuntu-linux:~# ls -l /var/happy
-rw-r--r-- 1 root root 0 Apr 15 10:53 /var/happy

As you can see, nothing can stop the root user from doing anything! Now let's create the directory games in /etc:

root@ubuntu-linux:~# mkdir /etc/games 
root@ubuntu-linux:~# ls -ld /etc/games
drwxr-xr-x 2 root root 4096 Apr 15 10:55 /etc/games

We got no error, and that's because you have the power to do whatever you want as the root user. But ALWAYS remember, with great power comes great responsibility.

Setting the root password

You can also use the su command to switch to the root user but first, you need to set the root's password:

root@ubuntu-linux:~# passwd 
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Amazing, now exit the root user:

root@ubuntu-linux:~# exit 
logout
elliot@ubuntu-linux:~$ whoami 
elliot

Now you can use the su root command to switch to the root user:

elliot@ubuntu-linux:~$ su root 
Password:
root@ubuntu-linux:/home/elliot# whoami 
root

The dash difference

Notice that my current working directory is now /home/elliot and not /root. If I want to change that, I can exit back to user elliot and rerun the su command but this time, I will add a dash (hyphen) before root as follows:

root@ubuntu-linux:/home/elliot# exit 
exit
elliot@ubuntu-linux:~$ su - root 
Password:
root@ubuntu-linux:~# pwd
/root

So what is the difference?

Here's the deal. When you don't add the dash before the username, the shell preserves the current user shell environment settings, which includes the current working directory. On the other hand, when you add the dash, the shell acquires the environment settings of the new user (the user you switched to).

So let's do some practice. If you want to switch to user elliot but preserve root's shell environment settings, then you don't need the dash:

root@ubuntu-linux:~# pwd
/root
root@ubuntu-linux:~# su elliot 
elliot@ubuntu-linux:/root$ pwd
/root
elliot@ubuntu-linux:/root$

Notice how the current working directory didn't change when I switched to user elliot. Now, let's exit and switch back again to user elliot, but this time, we will put a dash before the username:

elliot@ubuntu-linux:/root$ exit 
exit
root@ubuntu-linux:~# pwd
/root
root@ubuntu-linux:~# su - elliot 
elliot@ubuntu-linux:~$ pwd
/home/elliot

Now notice how the current working directory changed from /root to /home/elliot. So here, the shell acquired the environment settings of user elliot.

Let's try out our cool tip! As user elliot, run the su command without specifying a username:

elliot@ubuntu-linux:~$ su 
Password:
root@ubuntu-linux:/home/elliot#

You can then enter the root password to log in as root.

You can also use the dash to acquire root's shell environment settings:

elliot@ubuntu-linux:~$ su - 
Password:
root@ubuntu-linux:~# pwd
/root

This time I landed in /root because I used the dash.

Well, this was a short chapter, but the root user certainly deserves a whole section by itself. Also, remember that you have got superpowers when you are the root user as you have the permission to do anything on your system. And so if you are not very careful, you can damage your system, and that's why there is a very famous Linux meme that says, "Don't drink and root!."

Knowledge check

For the following exercises, open up your Terminal and try to solve the following tasks:

1. Switch to the root user.
2. Change the password for the root user.
3. Switch to user elliot and land in /home/elliot.
4. Now switch to user root but preserve the current working directory /home- /elliot.

True or false

1. The root user is the most powerful user in Linux.
2. Using the su command without specifying a username will switch you to the root user.
3. We use the passroot command to change the password for the root user.