⣿ ZOTHOS × 1NC0GN30 30 DAYS OF LINUX FUNDAMENTALS · TUI (./control-panel) + WEB GUI · 90 MISSIONS
1nc0gn30.si ↗ ZothOS v3.4 ↗ ZothOS-Lite ↗ GitHub Repo ↗
← Back to 30-Day Curriculum

WEEK 3 · SECURITY & WORKFLOWS · TUI: ./control-panel --day 21

Day 21: User & Group Administration, Sudoers & PAM Security

Provision operator accounts, enforce password aging policies, and manage least-privilege sudoers access.

XP 0
Streak 0
Command Mastery 0%
Study Music

YouTube Study Radio

Pick a track or paste any YouTube URL.

🍳 Breakfast (Syntax) Session

Type commands, build streaks, and then review the source guide.

Live Terminal Drill

Re-type the command exactly to clear each challenge.

target$ loading...

0 / 12 mastered

    Command Board

    Tap a command when you practiced it in your own terminal.

    Command Intel

    Meaning

    Command explanation will appear here.

    Sample Output

    Output preview will appear here.

    Useful Fun Fact

    Fun facts about the active command will appear here.

    Last Run Output

    Run a command to see result feedback.

    Knowledge Boost

    Faster learning with topic cues, mini-missions, and external docs.

    Key Topics

    ⚡ 60-Second Mental Model (Student Digest)🧠 Objective🔐 Section 1: Security Best PracticesKey Concepts:Practice:

    Mini Missions

    • Mission 1: Run useradd and explain the output in one sentence.
    • Mission 2: Run usermod and explain the output in one sentence.
    • Mission 3: Run userdel and explain the output in one sentence.
    • Mission 4: Run groupadd and explain the output in one sentence.

    Useful Resources

    📖 Digestible Study Guide & Visual Architecture

    Source: day-21-breakfast-guide.md · Synced with ./control-panel --day 21

    Day 21 · Breakfast — User & Group Administration, Sudoers & PAM Security



    ZothOS × 1nc0gn30 Linux Dojo · Phase: Week 3 (Security & Workflows) · Session: Breakfast (Morning Foundation & Core Command Syntax)

    Core Commands: useradd, usermod, userdel, groupadd, passwd, chage


    ⚡ 60-Second Mental Model (Student Digest)



    ╔══════════════════════════════════════════════════════════════════════════════╗
║  ZOTHOS × 1NC0GN30 // DEFENSE-IN-DEPTH & STREAM PIPELINE ARCHITECTURE        ║
╠══════════════════════════════════════════════════════════════════════════════╣
║                                                                              ║
║  [ INBOUND PACKET ] ──► [ Netfilter: iptables / nftables ]                   ║
║                                │ (ACCEPT)                                    ║
║                                ▼                                             ║
║                         [ Hardened SSHD + Fail2Ban ]                         ║
║                                │                                             ║
║                                ▼                                             ║
║                         [ DAC: chmod/chown ] ──► [ MAC: SELinux / AppArmor ] ║
║                                │                                             ║
║                                ▼                                             ║
║                         [ Auditd & Log Pipelines: grep | awk | sed ]         ║
╚══════════════════════════════════════════════════════════════════════════════╝


    Learning PillarHow to Practice This Session
    1. Native TUI (./control-panel)Run ./control-panel from repo root → Select Week 3 → Day 21 → Breakfast to drill interactive C lessons & quizzes.
    2. Web Workstation (astro-ui)Open /day/21 → Select Breakfast tab → Type each target command in the live Mission Terminal to earn XP & streak mastery.
    3. Safe Local SandboxRun mkdir -p /tmp/linux-dojo-day-21 && cd /tmp/linux-dojo-day-21 to test every flag below without touching production files.



    🥣 Day 21 Breakfast: Week 3 Recap



    🧠 Objective


    Reinforce foundational security practices from Week 3 by reviewing:
  • User and group permissions

  • Firewall hardening

  • IDS fundamentals

  • Backup & recovery strategies




    • 🔐 Section 1: Security Best Practices



    Key Concepts:


  • Use chmod, chown, and groups to enforce least privilege

  • Disable unused users:

    • sudo passwd -l
  • Grant sudo access securely:

    • sudo usermod -aG sudo

    Practice:


    ```bash
    sudo useradd -m secure_user
    sudo passwd secure_user
    sudo usermod -aG sudo secure_user
    sudo chmod 700 /home/secure_user

    🛡️ Section 2: Advanced Network Hardening
    Key Commands:

    sudo iptables -F
    sudo iptables -P INPUT DROP
    sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT
    sudo iptables-save > /etc/iptables.rules

    SSH Hardening Tips:

    Disable root login: PermitRootLogin no

    Use key auth only: PasswordAuthentication no

    Set idle timeout: ClientAliveInterval, ClientAliveCountMax

    💾 Section 3: Backups & Disaster Recovery
    Practice:

    Backup /etc


    tar -czvf /backups/etc_backup.tar.gz /etc

    Automate backups


    echo "0 2 * tar -czf /backups/home_$(date +\%F).tar.gz /home" | sudo tee /etc/cron.d/home_backup

    Verify file integrity


    sha256sum -c backup_checksums.txt

    ✅ Quiz Topics (In breakfast-day-21)

    chmod syntax and modes

    IDS use cases (Snort, Wireshark)

    SELinux command basics

    ✅ Summary

    By the end of this section, you should:

    Know how to create and secure users

    Understand baseline firewall configuration

    Be able to perform and verify a backup

    Recognize core IDS tools and their purpose