In the last chapter, we set up our very own Ubuntu Server installation. During the installation process, we were instructed to create a user account as an administrator of the system. So, at this point, we should have two users on our server. We have the aforementioned administrative user, as well as root. We can certainly create additional user accounts with varying levels of access (and we will do so in this chapter), but before we get to that, some discussion is in order regarding the administrator account you created, as well as the root user that was created for you.

In regards to root, the root user account exists on all Linux distributions and is the most powerful user account on the planet. The root user account can be used to do anything, and I do mean anything. Want to use root to create files and directories virtually anywhere on the file-system? No problem. Want to use root to install software? Again, not a problem. The root account can even be used...

Creating users in Ubuntu can be done with one of either of two commands: adduser and useradd. This can be a little confusing at first, because both of these commands do the same thing (in different ways) and are named very similarly. I'll go over the useradd command first and then I'll explain how adduser differs. You may even prefer the latter, but we'll get to that in a moment.

First, here's an example of the useradd command in action:

# useradd -d /home/jdoe -m jdoe

# sudo useradd -d /home/jdoe -m jdoe

In this example...

Now that we know how to create (and delete) user accounts on our server, we are well on our way to being able to manage our users. But where exactly is this information stored? We know that users store their personal files in /home, but is there some kind of database somewhere that keeps track of which user accounts are on our system? Actually, user account information is stored in two special text files: /etc/passwd and /etc/shadow.

You can display the contents of each of those two files with the following commands. Take note that any user can look at the contents of /etc/passwd, while only root has access to /etc/shadow:

# cat /etc/passwd
# cat /etc/shadow

Go ahead and take a look at these two files (just don't make any changes), and I will help you understand them. First, let's go over the /etc/passwd file. What follows is example output from this file on my test server. For brevity, I limited the output to the last seven lines:

testuser...

In a typical organization, there are usually some defaults that are recommended for users in terms of files and configuration. For example, in a company that performs software development, there are likely recommended settings for text editors and version control systems. Files that are contained within /etc/skel are copied into the home directory for all new users when you create them (assuming you've chosen to create a home directory while setting up the user).

In fact, you can see this for yourself right now. If you execute the following command, you can view the contents of the /etc/skel directory:

ls -la /etc/skel

You probably already know how to list files within a directory, but I specifically called out the -a parameter because the files included in /etc/skel by default are hidden (their file names begin with a period). I threw the -l parameter solely because I like it better (it shows a long list, which I think is easier to read...

Now that we have several users on our system, we need to know how to switch between them. Of course, you can always just log in to the server as one of the users, but you can actually switch to any user account at any time providing you either know that user's password or have root access.

The command you will use to switch from one user to another is the su command. If you enter su with no options, it will assume that you want to switch to root and will ask you for your root password. As I mentioned earlier, Ubuntu locks out the root account by default, so you really don't have a root password. Unlocking the root account is actually really simple; all you have to do is create a root password. To do that, you can execute the following command as any user with sudo access:

sudo passwd

The command will ask you to create and confirm your root password. From this point on, you will be able to use the root account as any other account. You can log in as root, switch to root...