MODULE 2: Users, Permissions & Identity Management

How do enterprises manage users securely and control who can access what on Linux servers?

What You Will Learn in This Module

By the end of Module 2, learners will be able to:

• Create and manage Linux users
• Understand user groups and group-based access
• Apply file and folder permissions correctly
• Use sudo for administrative tasks
• Protect servers from unauthorized access
• Apply enterprise access control best practices

Lesson 1: Linux Users Explained Simply

Linux is a multi-user system.

Every person or service has:

• a username
• a user ID
• permissions

Users include:

• human users
• system accounts
• application accounts

Enterprise Concept

Never share accounts.

Each admin must have their own user.

This supports:

• auditing
• accountability
• security

Lesson 2: Creating, Modifying & Deleting Users

Admins manage users using commands like:

• useradd
• usermod
• userdel

Typical enterprise tasks:

• create new employee account
• disable leaving employee
• reset passwords
• lock compromised accounts

Example Workflow

New employee joins:

1. create user
2. assign group
3. set password
4. give sudo if needed
5. document access

Lesson 3: Linux Groups (Powerful & Clean Access Control)

Instead of managing permissions per user, enterprises use groups.

Example groups:

• developers
• admins
• finance
• support

Files and services are assigned to groups.

Then users are added/removed from groups.

Why Groups Matter

Change once → affects many users.

Clean, scalable security.

Lesson 4: File Ownership & Permission Model

Each file has:

• owner
• group
• permissions

Permissions:

• r (read)
• w (write)
• x (execute)

Displayed like:
rwxr-x—

Meaning:
Owner full access
Group read+execute
Others no access

Enterprise Example

Finance folder:

• owner: finance_admin
• group: finance_team
• others: no access

This protects sensitive data

Lesson 5: chmod, chown & chgrp (Permission Tools)

Admins use:

• chmod → change permissions
• chown → change owner
• chgrp → change group

Used to:

• protect data
• restrict access
• assign ownership

Lesson 6: sudo: Safe Administrative Access

Instead of logging in as root:

Admins use sudo.

Benefits:

• tracks admin actions
• prevents accidents
• supports role separation

Enterprise rule:
X: no direct root login

• controlled sudo access

Lesson 7: Password Policy & Account Security

Enterprises enforce:

• strong passwords
• password expiry
• account lockout
• disabling inactive users

Admins configure:

• password complexity
• login attempts
• aging policies

This reduces attack risk.

Lesson 8: SSH Access Control

Servers are accessed via SSH.

Best practices:

• disable root SSH login
• use key-based authentication
• restrict SSH to specific Ips
• change default port (optional)
• monitor SSH logs

Lesson 9: Preventing Unauthorized Access

Admins must protect servers from:

• brute-force attacks
• unauthorized users
• compromised credentials

Using:

• firewalls
• fail2ban
• log monitoring
• least privilege

Security is layered.

Lesson 10: Practical Self Practice

Learners practice:

• creating users
• creating groups
• assigning permissions
• testing access
• enabling sudo
• locking accounts

Scenario:
New employee joins → setup account
Employee leaves → disable access

This mirrors real enterprise workflow.

 

MODULE 2 SUMMARY

By completing Module 2, learners now understand:

• Linux users and groups
• access control using permissions
• sudo administration
• password policies
• SSH security basics
• enterprise identity management mindset

This module answers:

“How do I manage users securely and control access on Linux servers?”