Notes

Linux Linux Index

4 min read

Linux Mastery Syllabus (DevOps / SRE Focus)

🧱 PHASE 1 — Core System Understanding (Foundation but Deep)

1. Linux Architecture

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👉 Output Skill:

  • You can explain how a system boots and where things can break

2. Filesystem & Storage

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  • Linux filesystem hierarchy (/etc, /var, /usr, /home)
  • Inodes & file metadata
  • Mounting & partitions
  • File types (links, sockets, pipes)

👉 Practice:

  • Mount a disk manually
  • Recover deleted file (inode understanding)

3. Permissions & Ownership

  • chmod, chown, umask

  • SUID, SGID, Sticky bit

  • ACLs (setfacl, getfacl)

👉 Real-world:

  • Secure SSH directories

  • Restrict app access

⚙️ PHASE 2 — Process, Memory & System Control

4. Process Management

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  • Process lifecycle

  • Foreground/background jobs

  • Signals (kill, SIGTERM, SIGKILL)

  • Monitoring (top, htop, ps, nice)

👉 Practice:

  • Kill stuck processes safely

  • Prioritize processes

5. Systemd & Services (CRITICAL)

  • systemctl (start, stop, restart)

  • Unit files

  • Journald logs

👉 Real-world:

  • Debug failed services

  • Create custom service

6. Memory Management

  • RAM vs Swap

  • Cache, buffers

  • Tools: free, vmstat, top

👉 Debug:

  • High memory usage issues

🌐 PHASE 3 — Networking (VERY IMPORTANT FOR DEVOPS)

7. Linux Networking Basics

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  • IP, DNS, routing

  • /etc/hosts, /etc/resolv.conf

  • Commands: ping, curl, wget

8. Advanced Networking

  • netstat, ss, tcpdump

  • Ports & sockets

  • Firewall (iptables, ufw)

👉 Practice:

  • Debug “service not reachable”

  • Open/close ports

🧑‍💻 PHASE 4 — Shell & Automation (GAME CHANGER)

9. Bash & Shell Scripting

  • Variables, loops, conditions

  • Functions

  • Cron jobs

👉 Build:

  • Backup script

  • Log cleanup script

  • Deployment script

10. Text Processing Tools

  • grep, awk, sed, cut, sort

👉 Real-world:

  • Parse logs

  • Extract metrics

📦 PHASE 5 — Package & Software Management

11. Package Managers

  • apt, yum, dnf

  • Repositories

12. Build & Install Software

  • Compile from source (make, gcc)

  • Environment variables

🔐 PHASE 6 — Security (VERY IMPORTANT)

13. Linux Security Basics

  • SSH hardening

  • Fail2ban

  • User privilege control

14. Advanced Security

  • SELinux / AppArmor

  • File auditing

👉 Practice:

  • Secure a server from scratch

📊 PHASE 7 — Monitoring & Logs (SRE CORE)

15. Logs & Debugging

  • /var/log

  • journalctl

👉 Debug:

  • Why service failed

  • Why app crashed

16. Monitoring Tools

  • top, htop

  • Disk: df, du, iostat

🧪 PHASE 8 — Advanced System Topics

17. Disk & Storage Advanced

  • RAID

  • LVM

18. Containers & Linux Internals

  • Namespaces

  • cgroups

👉 Connect to:

  • Docker & Kubernetes internals

🚀 PHASE 9 — Real DevOps Scenarios (MOST IMPORTANT)

🧨 Practice Scenarios:

  • Server not booting

  • Disk full issue

  • High CPU usage

  • Service failing

  • Network unreachable

  • SSH not working

👉 THIS is what companies test

🧠 Final Output (After Completing This)

You should be able to:

  • Debug ANY Linux issue

  • Handle production servers

  • Crack DevOps interviews

  • Work confidently with Kubernetes nodes

⚡ Bonus (What Makes You TOP 1%)

  • Write bash automation scripts daily

  • Break your VM intentionally

  • Learn debugging mindset (not commands)

🔥 If you want next level:

I can create:

  • 📅 30-day strict roadmap (daily tasks)

  • 🧪 Hands-on lab exercises (real production issues)

  • 🎯 Linux interview questions for DevOps roles

Just tell me 👍

1. To Check File Size

Use the ls -lh command for a human-readable file size:

ls -lh
  • -l: Long listing format
  • -h: Human-readable sizes (e.g., KB, MB, GB)

Output Example:

-rw-r--r--  1 user user  4.0K Jan  3 12:00 example.txt

Here, 4.0K is the size of the file.

2. To Check Directory Size

Use the du (disk usage) command:

du -sh [directory_name]
  • -s: Summary of the total size
  • -h: Human-readable format

Example:

du -sh /home/user

Output:

2.1G    /home/user

This shows the total size of the directory.

3. To See Sizes of All Files and Subdirectories

To list sizes of all files and subdirectories in a directory:

du -h [directory_name]

4. Sort Files by Size

Use ls with the -S flag to sort files by size:

ls -lSh
  • -S: Sort by file size (largest first)
  • -h: Human-readable

5. Check Free Disk Space

To see free and used disk space:

df -h
  • df: Disk space usage
  • -h: Human-readable format

Example Output:

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       50G   20G   30G  40% /

Let me know if you need more help with CLI commands! 🚀

to assigin any command to shortcut

alias k=kubectl #Directly inside terminal

command to list all running processes, and filters the outpu

List processes

ps -ef | grep -i

grep command to show 10 lines below search

`openssl x509 -in /etc/kubernetes/pki/apiserver.crt -text -noout | grep -i -A 10 altern`

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