Guides

How to Add a User in Linux, Set a Password and Give sudo Access

By Ravindra Bagale, AWS & DevOps trainer · LinkedIn · Published: 16 October 2026 · Last updated: 17 October 2026

To add a user in Linux, run sudo adduser priya on Ubuntu/Debian, or sudo useradd -m priya then sudo passwd priya on Amazon Linux, RHEL and CentOS. To give admin rights, add the user to the sudo group (Ubuntu) or the wheel group (Amazon Linux/RHEL) with sudo usermod -aG. On EC2, put the user's public SSH key in /home/priya/.ssh/authorized_keys, so each person logs in with their own account.

# Ubuntu / Debian
sudo adduser priya
sudo usermod -aG sudo priya

# Amazon Linux 2023 / RHEL / CentOS
sudo useradd -m -s /bin/bash priya
sudo passwd priya
sudo usermod -aG wheel priya

id priya        # check groups

A live example first

Three trainees join a project. Until now, everyone logged in to the Amazon Linux 2023 server as ec2-user with the same .pem key. We give Priya her own account, with sudo, and her own key.

1. Create the user and add her to wheel:

sudo useradd -m -s /bin/bash priya
sudo usermod -aG wheel priya
id priya

uid=1001(priya) gid=1001(priya) groups=1001(priya),10(wheel)

2. Priya creates a key pair on her own laptop and sends you only the public key:

ssh-keygen -t ed25519 -C "priya-laptop"
cat ~/.ssh/id_ed25519.pub

3. On the server, add it with the right owner and permissions:

sudo mkdir -p /home/priya/.ssh
echo "ssh-ed25519 AAAAC3Nza...xyz priya-laptop" | sudo tee /home/priya/.ssh/authorized_keys
sudo chown -R priya:priya /home/priya/.ssh
sudo chmod 700 /home/priya/.ssh
sudo chmod 600 /home/priya/.ssh/authorized_keys

4. Because she logs in with a key and has no password, allow sudo without a password for wheel, or set a password with sudo passwd priya so sudo can ask for it.
5. Priya tests from her laptop:

ssh priya@<PUBLIC_IP>
sudo -v && echo "sudo works"

Now the logs in /var/log/secure show priya instead of a shared ec2-user. Friends, when she leaves the project, we remove only her account. Nobody else has to change keys.

How do Linux users and groups work?

Each user has a UID, a home folder and a login shell, stored in /etc/passwd (passwords are hashed in /etc/shadow). Groups are in /etc/group. sudo reads /etc/sudoers, which on Ubuntu allows the sudo group and on RHEL-family systems allows the wheel group to run commands as root.

How do I add a user step by step?

1. Choose a username (lowercase, no spaces).
2. Create the user with a home folder (adduser or useradd -m).
3. Set a password, or plan for key-only login.
4. Add groups: sudo/wheel only if they really need admin rights, docker only if they must run containers (it is root-equivalent), www-data or apache to share web files.
5. Add their SSH public key.
6. Test the login in a new terminal before closing your own session.
7. Write down who has which access.

Useful user commands

Safer sudo with sudoers.d

Never edit /etc/sudoers directly. Use a small file and check it:

echo "priya ALL=(ALL) NOPASSWD: /usr/bin/systemctl restart nginx" | sudo tee /etc/sudoers.d/priya
sudo chmod 440 /etc/sudoers.d/priya
sudo visudo -c

This lets Priya restart nginx and nothing else. That is least privilege.

App users, per stack

Apps should also run as their own non-login users, not as root:

-r makes a system user, and /sbin/nologin stops anyone from logging in as it.

Real example: why shared logins hurt

In the SolarWinds investigation (2020–2021), company leaders told the US Congress that an intern had set a weak password, "solarwinds123", on an update server, and that it was found exposed on GitHub. Whatever its role in the bigger attack, the lesson for every team is clear: shared, weak credentials are hard to track and hard to take back. Personal accounts, SSH keys and least-privilege sudo make every action traceable to one person.

Mistakes to avoid

1. usermod -G sudo without -a. It removes the user from all other groups.
2. Pasting a private key on the server. Only the public key (.pub) goes in authorized_keys.
3. Wrong permissions on .ssh. SSH ignores keys if the folder or file is writable by others.
4. Giving everyone sudo. Most people need only a few commands.

Summary table