Introduction
One of the most basic tasks that you should know how to do on a fresh Linux server is add and remove users. When you create a new system, you are often only given the root account by default. While running as the root user gives you a lot of power and flexibility, it is also dangerous and can be destructive. It is almost always a better idea to add an additional, unprivileged user to do common tasks. You should then create additional accounts for any other users you may have on your system.
You can still acquire administrator privileges when you need them through a mechanism called sudo. In this tutorial, you’ll learn how to create user accounts, assign sudo privileges, and delete users.
How To Add a User
If you are signed in as the root user, you can create a new user at any time by typing:
adduser sammy
If you are signed in as a non-root user who has been given sudo privileges, as demonstrated in the initial server setup guide, you can add a new user by typing:
sudo adduser sammy
Once you execute the command, you’ll see some output, followed by series of prompts asking you to assign and confirm a password for the new user. Then you’ll be asked to enter any additional information about the new user. This is entirely optional and can be skipped by hitting ENTER if you don’t wish to enter information into these fields.
Finally, you’ll be asked to confirm that the information you provided was correct. Enter Y to continue. The whole process looks like this:
Adding user `sammy' ...
Adding new group `sammy' (1001) ...
Adding new user `sammy' (1001) with group `sammy' ...
Creating home directory `/home/<^>sammy' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for sammy
Enter the new value, or press ENTER for the default
Full Name []: Sammy the Shark
Room Number []: 123
Work Phone []: 555-555-5555
Home Phone []:
Other []:
Is the information correct? [Y/n] y
The adduser command created a user, a group, and a home directory for your user. Your new user is now ready for use! You can now log in using the password you set up.
Note: Continue if you need your new user to have access to administrative functionality.
How To Grant a User Sudo Privileges
If your new user needs to execute commands with root privileges, you will need to give the new user access to sudo. Let’s examine two approaches to this problem: Adding the user to a pre-defined sudo user group, and specifying privileges on a per-user basis in sudo’s configuration.
Add the New User to the Sudo Group
By default, sudo on Debian 8 systems is configured to extend full privileges to any user in the sudo group.
You can see what groups your new user is in with the groups command:
groups sammy
sammy : sammy
By default, a new user is only in their own group, which is created at the time the account was created, and shares a name with the user. In order to add the user to a new group, use the usermod command:
usermod -aG sudo sammy
The -aG option here tells usermod to add the user to the listed groups.
Use the groups command again to verify that your user is now a member of the sudo group:
sammy : sammy sudo
Now, your new user is able to execute commands with administrative privileges.
When signed in as the new user, you can execute commands as your regular user by typing commands as normal:
ls ~
You can execute commands with administrative privileges by typing sudo in front of the command:
sudo ls /root
When prefixing a command with sudo, you will be prompted to enter a password. Enter the password for the user account that issued the command, not the root user’s password.
Specifying Explicit User Privileges in /etc/sudoers
As an alternative to putting your user in the sudo group, you can use the visudo command, which opens a configuration file called /etc/sudoers in the system’s default editor, and explicitly specify privileges on a per-user basis.
Editing the /etc/sudoers/ file offers more flexibility, but should only be used when you need this flexibility, as it requires more maintenance when managing user accounts.
Using visudo is the only recommended way to make changes to /etc/sudoers, because it locks the file against multiple simultaneous edits and performs a sanity check on its contents before overwriting the file. This helps to prevent a situation where you misconfigure sudo and are prevented from fixing the problem because you have lost sudo privileges.
If you are currently signed in as root, type:
visudo
If you are signed in using a non-root user with sudo privileges, type:
sudo visudo
Traditionally, visudo opened /etc/sudoers in the vi editor, which can be confusing for inexperienced users. By default on new Debian installations, it should instead use nano, which provides a more familiar text editing experience. Use the arrow keys to move the cursor, and search for the line that looks like this:
/etc/sudoers
root ALL=(ALL:ALL) ALL
Below this line, copy the format you see here, changing only the word “root” to reference the new user that you would like to give sudo privileges to:
/etc/sudoers
root ALL=(ALL:ALL) ALL
sammy ALL=(ALL:ALL) ALL
You should add a new line like this for each user that should be given full sudo privileges. When you are finished, you can save and close the file by hitting CTRL-X, followed by Y, and then ENTER to confirm.
How To Delete a User
In the event that you no longer need a user, it is best to delete the old account.
You can delete the user itself, without deleting any of their files, by typing this as root:
deluser sammy
If you are signed in as another non-root user with sudo privileges, you could instead type:
sudo deluser sammy
If you want to delete the user’s home directory when the user is deleted, issue the following command as root:
deluser --remove-home sammy
If you’re running this as a non-root user with sudo privileges, you would instead type:
sudo deluser --remove-home sammy
If you had previously configured sudo privileges for the user you deleted by editing the /etc/sudoers file, you should remove the relevant line in the file by typing:
visudo
Or use this if you are a non-root user with sudo privileges:
sudo visudo
Then locate the line in the file associated with your user and remove it.
root ALL=(ALL:ALL) ALL
sammy ALL=(ALL:ALL) ALL # DELETE THIS LINE
This will prevent a new user created with the same name from being accidentally given sudo privileges.
Conclusion
You should now have a good handle on how to add and remove users from your Debian 8 system. Effective user management will allow you to separate users and give them only the access that they are required to do their job.
For more information about how to configure sudo, check out our guide on how to edit the sudoers file here.
