Over the last few weeks, I took a deep dive into the world of Linux system administration by studying the Red Hat System Administration (RHSA) course — not for the certification, but for the knowledge. As a student in cybersecurity aiming to specialize in Red Teaming, understanding Linux inside-out is a must.
Although I didn’t pursue the official certificate this time, I focused on understanding and practicing the core concepts. Here’s a breakdown of what I learned and what I’m working on right now.
🧠 What I Learned
- 🧬 The Evolution: From Unix to Linux to Modern Distros
Understanding the history of Unix and the philosophy behind Linux was an eye-opener. I learned how:
Unix influenced the modular and powerful nature of Linux
Different Linux distributions emerged for different purposes (e.g., Red Hat for enterprise, Debian for stability, Arch for customization, etc.)
System architecture is structured, and how it differs slightly across distros
- 📁 File Control
I learned how to:
Navigate the Linux filesystem efficiently using cd, ls, pwd, and tree
Work with files and directories: cp, mv, rm, touch, mkdir
Use redirection and piping (>, >>, <, |) to control input/output flows
- 👥 User Control
Managing users is critical in system security. I practiced:
Creating/deleting users with useradd, userdel
Modifying user data with usermod, passwd
Switching and working as different users with su and sudo
Managing user profiles and login behavior
- 🔐 Permissions & Groups
Security starts with permissions. I explored:
Understanding file permissions (rwx, numbers like chmod 755)
Changing ownership with chown, and permissions with chmod
Managing groups with groupadd, usermod -aG, etc.
The concept of umask and default permissions
- 🔍 Searching and Filtering
I got comfortable using:
find for locating files based on size, time, name
grep and its power in filtering and pattern matching
Combining tools like grep | sort | uniq for advanced filtering
- 💻 Shell Scripting (Bash)
This was the most fun part! I wrote scripts that:
Automate repetitive tasks
Handle user input, arguments, loops, and conditions
Include logging, backups, and simple error checking
- 🌟 Wildcards
I learned to use:
*, ?, [] in powerful ways to match patterns in filenames or command-line arguments
Combine wildcards with other tools like ls, rm, and grep to make powerful one-liners
- 🔎 Regular Expressions (Regex)
Regex felt like magic. I used it to:
Match complex patterns in logs and text files
Filter email addresses, IPs, error messages
Combine it with tools like grep, sed, awk
- ⏰ Task Scheduling with Cron
Task scheduling is a must-have for system admins. I learned how to:
Use crontab to schedule repetitive tasks like backups and script execution
Understand cron time syntax
Manage both user-level and system-wide jobs
Example:
0 3 * * * /home/user/backup.sh
This runs a backup script every day at 3 AM.
🛠️ What's Next — The Practical Phase
I'm now in the practical application phase — where I'm:
Building and managing a virtual Linux environment (using VirtualBox + CentOS & Ubuntu)
Writing daily-use scripts (e.g., backup automation, user report generation)
Practicing security hardening techniques
Exploring log management and cron job automation
The goal is to move from “I know how this works” to “I can build and maintain this myself”.
🎯 Final Thoughts
Although I didn't aim for the certification yet, this learning path has strengthened my confidence in handling Linux systems — which is essential for my Red Teaming journey. I plan to continue building my skills with:
CTFs focused on Linux exploitation
More advanced Bash scripting projects
Networking and system hardening practices
By the way, some people know me as Seif Eldin Ahmed Mohamed or Seif A. Mohammad - but I'm always Seif Eldien Ahmad Mohammad 😄. I had to assure my name is spelt right.
Thanks for reading. If you're also on a similar path or learning RHSA, feel free to connect — let’s grow together!
🔗 Let’s connect:
LinkedIn: https://www.linkedin.com/in/seifeldienahmad/
GitHub: https://github.com/SeifEldienAhmad/
Website: https://seifeldienahmad.github.io/
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