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Cyber Security Academy · Lesson

User and Group Management

Add, remove, and audit users and groups, configure sudo, and apply the principle of least privilege.

Linux User Model

Linux is a multi-user OS. Every process runs as a specific user. Understanding users and groups is fundamental to access control and privilege separation.

The /etc/passwd File

/etc/passwd stores user account information: username, UID, GID, home directory, shell. Passwords are stored (as hashes) in /etc/shadow, readable only by root.

cat /etc/passwd
# format: username:x:UID:GID:comment:home:shell

All lessons in this course

  1. File Permissions and Ownership
  2. User and Group Management
  3. SSH Hardening and Key-Based Auth
  4. iptables and UFW Firewall Rules
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