Ubuntu Admin Group: How to Create and Manage Users and Groups

Introduction

I’m primarily a Windows administrator, but occasionally I manage Linux systems too—specifically Ubuntu Server. In this article, I’m working with Ubuntu 20.04 LTS. Since I don’t use Linux every day, I often need a quick refresher when it comes to user and permission management.

That’s why I decided to write down the essential commands for creating users and groups, assigning permissions, and explaining the difference between the root user and users in the Ubuntu admin group (also known as the sudo group). If you’re like me and want a practical, no-frills guide to managing users and groups in Ubuntu, this one’s for you.

Managing Users and Groups

Managing users and permissions can be a pain. Administrators, by default, allow one user to manage the entire system. When you install Ubuntu Server 20.04 you will be asked to create a user. This user will automatically be added to the group sudo, which means the user obtains the highest rights in short sudo. Sudo access is crucial for managing user permissions effectively, as it allows users to execute commands with elevated privileges. In addition, Ubuntu creates another user which is called root user.

Understanding Users and Groups

Managing permissions in Linux involves understanding usernames, groups, and permissions. This article explains how these elements work together to control access. The superuser, or root user, has the highest system access. Managing these privileges is key for security.

Understanding users is crucial for access control. Each user needs a unique username, which identifies them on the system. Users need their own account and home directory. A sudo user can perform administrative tasks with limited access, adhering to the principle of least privilege.

Groups provide flexibility in managing users. While each user has a unique username, multiple users can belong to the same group, simplifying management while maintaining control over server tasks. Use command-line tools to verify a user’s group memberships and privileges.

Permissions are the final piece of access control. Linux uses a hierarchical permission system to determine user actions on files, directories, or applications.

In this article, you’ll learn to add a user to a sudo group and existing groups. A future article will cover permissions.

What is the sudo user, and when to use the sudo access

Ubuntu servers add the first created user to the sudo group, which means this user can use the sudo command to add other users and add/edit/delete system files. All of these operations require great privileges like adding a new user or adding a new group to add future users, adding them to the administrative groups(admin), and configuring permissions for each Linux file or folder. With sudo, users can perform various administrative tasks such as installing software, updating the system, and managing user accounts.

A user should only be added to the sudoers file when a user needs sudo permissions. The sudoers file is like the Administration group in Windows. All major tasks like adding users and adding groups can be done with root privileges by default or install/updated programs.

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Creating users and groups

Create a new user

There are two commands to add a user ‘useradd’ or ‘adduser’. At first, this can be a little confusing since both commands accomplish the same thing (in different ways) and are named similarly. I prefer the command ‘adduser’ since it creates the password for the user and the home folder with additional questions. ‘useradd” only adds the user to the system, and you would need to assign a password later.
When creating a new user, you can also provide additional information such as

to ensure comprehensive user details in the system.

The adduser command also creates a home directory for the user and a group with the same name as the user.

sudo adduser edy

Remove a user

Before removing an account, you should ask yourself one fundamental question: Is it still necessary for you to access the user’s files?

By default, this command won’t delete the user home directory or any files in it.

sudo userdel edy

Remove the user’s home directory with all its contents. It is not automatically deleted when you remove a user account. Also, remember that you may keep the folder for retention or move it elsewhere for archiving purposes.

sudo rm -r /home/edy

Create a new group

sudo groupadd admins

On the Ubuntu Server platform, you’ll likely see that each of your user accounts is a member of a group with the same name as your username. The moment you create a user account, you are also creating a group with the same name.

In this picture you see the home folder ‘edy’ (red), user permission (violet) and the automated created group ‘edy’ (green)

Add user to a group

To add a user to a group, you can use the usermod command as shown below:

sudo usermod -aG admins edy

The option -‘a’ means to append the user edy to the group. If you would not use ‘a’, all other existing memberships in the group would be removed. ‘G’ means to add the user to the secondary group. It adds the user to an additional group and won’t replace the primary group. To replace the user’s primary group, you would use ‘g’ lowercase instead of uppercase ‘G’.

To verify the user’s group membership, you can use the groups command:

groups edy

Remove a user from a group

gpasswd -d edy admins

This command will remove user ‘edy’ from the group ‘admins

What’s the difference between a primary group and a secondary group

The Primary Group is a group that is automatically created while creating a user. Similarly, a group with the same ID as the user is created and the user is added to the group as the only member. This group is referred to as the primary group.
When a user is added to the ‘sudo’ group, they will belong to their primary group and the sudo group.

We can create a secondary group independently using commands and add users to it by changing their group IDs.

Delete a group

sudo groupdel admins

How to check all groups in the system? There is a group file in /etc

nano /etc/group

In the file you see all groups. You also notice that groups are named after user name.

Switching users

su -edy

This command will change current user account to ‘edy’

If you only enter

su -

This will switch the user to ‘root’.

Since Ubuntu 20.04, Ubuntu installer won’t create the user ‘root’.

First, you must create a password for the user ‘root’. After that, you can switch to the ‘root’ user. Ubuntu recommends not using the root account. You add any other user to the sudo group. Remember that Ubuntu automatically added the user you created during the installation process to the sudo group.

To log into the server as the root user via SSH, you must enter the root account credentials to gain administrative control over the server’s shell.

Set password for user ‘root’

sudo passwd

You can set a ‘root’ password with any user who has sudo rights. Once the ‘root’ password is set, you can switch to the ‘root’ user. Using your password for sudo access ensures user accountability and control, allowing authorized users to perform administrative tasks without sharing the root password.

Setting a strong password for the root account is crucial to maintaining a robust security posture and preventing breaches caused by weak passwords.

Switching back from the ‘root’ user to your regular account, just type

exit

Add a user to sudo group (sudoers file)

sudo usermod -aG sudo edy

This will add the user ‘edy’ to the sudo group, granting them sudo privileges

groups edy

Look up the group membership of the user ‘edy’

Once added to the sudo group, the user can execute commands with elevated privileges using the sudo command. The sudoers file you find here /etc/sudoers.

Change password for a user

sudo passwd edy

I would love to get some feedback from you. Was this article helpful? Please share your opinion with me in the comment section below. Or, if you prefer a more personal touch, feel free to email me directly at info@edywerder.ch. Your thoughts and insights are always appreciated. Additionally, you can connect with me on Reddit at Navigatetech.