Easy February 2, 2026

TryHackMe – Linux Fundamentals Part 3

Power-up your Linux skills and get hands-on with some common utilities that you are likely to use day-to-day!

#cyber-security-101 #tryhackme #walkthrough

Answers

Edit “task3” located in “tryhackme“‘s home directory using Nano. What is the flag?

THM{TEXT_EDITORS}

Download the file http://MACHINE_IP:8000/.flag.txt onto the TryHackMe AttackBox. Remember, you will need to do this in a new terminal. What are the contents?

THM{WGET_WEBSERVER}

If we were to launch a process where the previous ID was “300”, what would the ID of this new process be?

301

If we wanted to cleanly kill a process, what signal would we send it?

SIGTERM

Locate the process that is running on the deployed instance (MACHINE_IP). What flag is given?

THM{PROCESSES}

What command would we use to stop the service “myservice”?

systemctl stop myservice

What command would we use to start the same service on the boot-up of the system?

systemctl enable myservice

What command would we use to bring a previously backgrounded process back to the foreground?

fg

When will the crontab on the deployed instance (MACHINE_IP) run?

@reboot

What is the IP address of the user who visited the site?

10.9.232.111

What file did they access?

catsanddogs.jpg

Things You Should Know

1. Terminal Text Editors

Nano

  • Beginner‑friendly command‑line text editor.

  • Create or edit files:

    nano filename

  • Important shortcuts:

    • Ctrl + X → Exit
    • Ctrl + O → Save
    • Ctrl + W → Search
    • Ctrl + K / Ctrl + U → Cut / Paste
    • Ctrl + _ → Go to line

  • Best for quick edits and configuration files.

VIM

  • Advanced and powerful editor with a steeper learning curve.

  • Features:

    • Custom keyboard shortcuts
    • Syntax highlighting (great for coding)
    • Available on most Linux systems

  • Preferred by developers and advanced users.

2. General / Useful Utilities (File Transfer & Sharing)

wget – Download Files

  • Downloads files from the web using HTTP/HTTPS.
wget https://example.com/file.txt
  • Common in servers and labs where no browser is available.

scp – Secure Copy (SSH)

  • Transfers files securely between two machines.
  • Local → Remote
scp file.txt user@ip:/path/file.txt
  • Remote → Local
scp user@ip:/path/file.txt local.txt

Python HTTP Server – Share Files

  • Quickly turn your machine into a simple web server:
python3 -m http.server
  • Files are served from the current directory on port 8000.
  • Other machines can download using wget.
  • Stops with Ctrl + C.
  • Limitation: no automatic directory indexing.

3. Processes 101

Understanding Processes

  • A process = running program.
  • Each has a PID (Process ID) assigned sequentially.
  • Managed by the kernel.

Viewing Processes

  • ps → current session processes.
  • ps aux → all processes on system.
  • top → real‑time CPU and memory usage.

Managing Processes

  • Stop processes with signals:

    • SIGTERM → clean shutdown.
    • SIGKILL → immediate kill.
    • SIGSTOP → pause.
kill PID

systemd & Namespaces

  • systemd is one of the first processes started at boot.
  • Controls services and child processes.
  • Namespaces isolate resources for security and stability.

Services with systemctl

systemctl start service
systemctl stop service
systemctl enable service
systemctl disable service
systemctl status service

Foreground vs Background

  • Run in background with &.
  • Pause with Ctrl + Z.
  • Bring back with:
fg

4. Automation – Cron Jobs

Cron & Crontabs

  • Used to schedule automatic tasks.
  • Edited with:
crontab -e
  • Format (6 fields):
MIN HOUR DOM MON DOW CMD

Example – backup every 12 hours:

0 */12 * * * cp -R /home/user/Documents /var/backups/
  • * acts as a wildcard.
  • Special keyword: @reboot runs tasks when the system starts.

5. Package Management (APT)

Repositories

  • Software comes from APT repositories.
  • You can add third‑party or community repos.

Key Commands

apt update
apt install package
apt remove package

Adding Repositories

  • Use add-apt-repository or manually add files in:
/etc/apt/sources.list.d/
  • GPG Keys verify software authenticity and security.

6. System Logs

Log Location

  • Stored in:
/var/log

Purpose

  • Monitor system health.
  • Troubleshoot errors.
  • Detect intrusions or suspicious activity.

Common Logs

  • Apache2 → web requests.
  • Fail2ban → brute‑force protection.
  • UFW → firewall activity.
  • Access logs → who accessed what.
  • Error logs → service/application issues.
  • Authentication logs → login attempts.

Logs are automatically managed through log rotation, preventing them from growing too large.

Overall Key Takeaways

Linux Fundamentals Part 3 teaches how to:

  • Edit files efficiently (Nano & VIM)
  • Transfer and share files (wget, scp, HTTP server)
  • View and control running programs (ps, top, kill, systemctl)
  • Run tasks automatically (cron jobs)
  • Install and manage software securely (APT & repositories)
  • Monitor and investigate system activity (logs)