01. Linux OS Architecture: Kernel vs User Space, System Calls & Process Management (ps, top, htop) • DevOps, Docker & Cloud VPS Deployment Mastery • Rishabh Ki Kaksha

DevOps, Docker & Cloud VPS Deployment Mastery › 01. Linux OS Architecture: Kernel vs User Space, System Calls & Process Management (ps, top, htop)

40 mins

Course Syllabus

Module 1: Linux System Administration & Kernel Performance Tuning

01. Linux OS Architecture: Kernel vs User Space, System Calls & Process Management (ps, top, htop) 02. Linux File Permissions (chmod, chown, SUID/SGID) & Sticky Bits Security 03. Networking & Diagnostics: netstat, ss, lsof, tcpdump, curl, dig & DNS Resolution

Part 1: Linux & Docker Containerization

Module 2: Containerization with Docker & Multi-Stage Builds

04. Docker Architecture: Namespaces, Cgroups, UnionFS & Docker Engine Internals 05. Dockerfile Optimization: Layer Caching, Non-Root Users & Ultra-Light Alpine Multi-Stage Builds 06. Docker Compose: Multi-Container Networking, Persistent Volumes & Environment Config 07. Docker Production Security: Read-Only Root FS, Capabilities Drop & Container Scanning

Part 2: Nginx, SSL, PM2 & Automated CI/CD

Module 3: Nginx Reverse Proxy, SSL Automation & Security Hardening

08. Nginx Masterclass: Event-Driven Non-Blocking Architecture vs Apache Multi-Threaded 09. Nginx as Reverse Proxy, Load Balancer (upstream) & Gzip/Brotli Compression Config 10. SSL/TLS Automation with Certbot Let's Encrypt, HTTP/2 & Strict-Transport-Security (HSTS) 11. Nginx Rate Limiting (limit_req), DDoS Mitigation & Security Headers Injection

Module 4: Process Management with PM2 & Systemd Services

12. Systemd Services: Creating Custom System Daemons with Automatic Restart & Logging 13. PM2 Enterprise Process Manager: Cluster Mode, Ecosystem Config & Graceful Reloads 14. Log Management & Rotation: logrotate, journalctl & Centralized Syslog Streaming

Module 5: CI/CD Automation with GitHub Actions & Zero-Downtime Deployments

15. CI/CD Foundations: Building Automated Test & Build Pipelines with GitHub Actions 16. Automated SSH Deployments: Self-Hosted Runners, Deploy Keys & Zero-Downtime Atomic Symlinks 17. Blue-Green & Canary Deployment Strategies on Cloud VPS Infrastructure

Module 6: Cloud VPS Production Hardening, Firewall (UFW) & Backups

18. Cloud VPS Hardening: Non-Root Sudo Users, SSH Key-Only Auth, Fail2ban & UFW Firewall Rules 19. Automated Database & Media Backups to Cloud Storage (AWS S3 / Cloudflare R2 / MinIO) 20. Server Health Monitoring & Alerting: Uptime Kuma, Netdata, Prometheus & Telegram Bot Webhooks

Interactive Lesson Studio

# 01. Linux OS Architecture: Kernel vs User Space, System Calls & Process Management (ps, top, htop)

> DevOps & Cloud VPS Notes by Rishabh - Topic 01

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### 1. Linux Architecture: Kernel vs User Space 🐧

*   **User Space (Ring 3):** Aapke applications (Node.js, Nginx, Python, MySQL) restricted memory me run hote hain. Hardware ya disk direct touch nahi kar sakte.
*   **Kernel Space (Ring 0):** Linux Kernel jo direct CPU, RAM, Network card aur Disk I/O control karta hai.
*   **System Calls (Syscalls):** User space se Kernel space switch karne ka bridge (`open()`, `read()`, `write()`, `fork()`, `epoll_wait()`).

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### 2. Linux Process Lifecycle & Signals 🚦

```
[ fork() ] ➔ [ RUNNING ] ➔ (I/O Wait) ➔ [ SLEEPING (Interruptible / Uninterruptible 'D' state) ]
                                                ⬇ (Exit)
                                      [ ZOMBIE ('Z' state) ] ➔ Parent calls wait() ➔ [ DEAD ]
```

*   `kill -15 <PID>` (`SIGTERM`): Graceful shutdown request (App cleans connections and exits).
*   `kill -9 <PID>` (`SIGKILL`): Kernel immediately forcefully terminates the process (Cannot be caught or ignored!).

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### 3. Essential Process Monitoring Commands

```bash
# Tree view of parent-child processes with memory & CPU:
ps aux --sort=-%mem | head -n 10

# Real-time interactive process viewer:
htop

# Find open file descriptors and listening network ports of a process:
lsof -p <PID>
```

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### 4. Master Comparison Matrix

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### 5. Interview Ke 3 Sawal Is Topic Se

1. **Zombie Process kya hota hai aur use kaise clean kiya jata hai?** -> Wo process jo terminate ho chuka hai par uske parent ne `wait()` system call nahi kiya; Zombie process CPU consume nahi karta par Process Table slot occupy karta hai; parent process ko kill karne se init/systemd use adopt karke reap kar leta hai.
2. **Uninterruptible Sleep (`D` state in top) ka kya matlab hota hai?** -> Process deep kernel disk/NFS I/O hardware response ka wait kar raha hai; ise `kill -9` se bhi instantly kill nahi kiya ja sakta jab tak I/O unblock na ho.
3. **Context Switch kya hota hai?** -> CPU ka ek process/thread ke registers aur memory context ko save karke doosre process ke context ko CPU par load karna (High context switching degrades system performance).

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**Next Topic:** 02. Linux File Permissions (chmod, chown, SUID/SGID) & Sticky Bits Security

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Rishabh Gehlot

PHP 8+ & Laravel 11 Master Track