On Linux systems, proper user management is the foundation of security, stability, and audit compliance. One incorrectly configured user with root access can become a vulnerability for the entire infrastructure. Therefore, a system administrator must know not only basic commands, but also groups, permissions, restrictions, and activity logging.

👥 Basic user management commands

Here are the basic commands everyone should know:

🛡️ Access control: rights, groups and sudo

📂 File and directory permissions

Linux uses three categories of permissions: owner, group and others. Each of them can have permissions to:

• r — read
• w — write
• x — execute

Example:

-rwxr-xr-- 1 user group 1234 Apr 5 10:00 file.txt

| 🔍 Use chmod, chown, chgrp to manage permissions and owners.

🔐 Sudo and groups

• Add user to sudo group:

usermod -aG sudo username

• Check who has sudo access:

getent group sudo

📁 Managing home directories and shells

• The home directory is created by default, but can be set manually:

useradd -m -d /home/new_path username

• The default shell can be set like this:

🧠 Audit and security logic

To avoid audit failure and simplify control:

✅ Disable unused accounts
✅ Regularly check groups and sudo rights
✅ Set up automatic removal of temporary users
✅ Enable logging of logins and sudo usage

sudo log file:

/var/log/auth.log

🔄 Automation with Ansible (optional)

Simple playbook example for user creation:

- name: Add new user 
  hosts: all
  become: true
  tasks:
    - name: Create user
      user:
        name: devops
        shell: /bin/bash
        groups: sudo
        append: yes

Effective user management in Linux is a balance between convenience and security. Setting up shells, permissions, and group policies can prevent errors and increase transparency in your infrastructure.

💡 Make your life easier, reduce risks, and always have a plan in case of an audit.