🚀 DevSecOps Journey — Day 20
Introduction to CI/CD & Jenkins Architecture (Hands-on Foundations)
After completing build tools, 2-tier & 3-tier applications, and NGINX, I’ve now moved into the heart of DevOps: CI/CD (Continuous Integration & Continuous Delivery).
This is where automation meets reliability, and where modern software delivery truly begins.
🔄 What is CI/CD? (Simple Explanation)
CI/CD is a pipeline of automated steps that ensures code is always ready for deployment.
A typical CI/CD flow looks like:
Code → Tests → Security Checks → Build → Deploy → Monitor
Each stage validates the code before moving forward, reducing failures in production.
🎯 Why CI/CD Is So Important
CI/CD helps organizations achieve:
⚙️ Automation – Less manual work
📜 Tracking & History – Every change is recorded
🧪 Early Testing – Bugs caught before deployment
🔐 Security Checks – Safer releases
🚀 Faster Deployments – Release with confidence
📈 Continuous Monitoring – Faster feedback loops
Because of CI/CD, code remains deploy-ready at all times.
🧰 Popular CI/CD Tools in Industry
🔹 Jenkins
Requires manual setup & maintenance
Runs on self-managed VMs
Uses Groovy for pipeline scripting
Highly customizable and widely adopted
🔹 GitHub Actions
Minimal setup effort
Free hosted runners available
Uses YAML workflows
Tight integration with GitHub repos
🔹 GitLab CI
Minimal setup effort
Free shared runners
Uses YAML
Built-in CI/CD experience
Each tool solves CI/CD differently, but Jenkins remains a core enterprise tool.
⚙️ Getting Started with Jenkins
Before running Jenkins:
- ☕ Java must be installed on the server/VM
🧱 Jenkins Architecture: Master–Agent Model
❌ Single Master Problem
If a single Jenkins master:
Runs Jenkins itself
Executes large pipelines (15–20 stages)
Has limited resources (e.g., 4GB RAM, 2 vCPU)
It can lead to:
Pipeline hangs
Failed jobs
❗ Error 137 (Out of Memory)
✅ Master–Agent Solution
Jenkins Master manages jobs & UI
Jenkins Agents (Slaves) execute pipelines
Workload is distributed across multiple VMs
📈 Result:
Better performance
No memory bottlenecks
Scalable CI/CD setup
🧩 Jenkins Job Types
Jenkins supports multiple job types:
🧱 Freestyle Jobs – Simple, UI-based tasks
🔁 Pipeline Jobs – Code-defined pipelines
🌿 Multibranch Pipelines – Auto-detect branches
Each is used depending on project complexity.
🛠 Jenkins Configuration Areas (Explored)
⚙️ System
Global server settings
Email notifications
Tool integrations
🔌 Plugins
Extend Jenkins capabilities
Git, Maven, Docker, Node, etc.
Older Java versions & third-party tools
🧰 Tools
Java versions
Maven / Node / Gradle
Configured globally
🖥 Nodes
Configure agent machines
Distribute workload
☁️ Cloud
Docker containers
Kubernetes pods
🔐 Credentials
Secure storage for:
Usernames
Passwords
Tokens
SSH keys
👥 Users & RBAC
Role-based access control
Secure Jenkins access
🎯 Why This Matters for DevOps / DevSecOps
Understanding CI/CD tools and Jenkins internals helps with:
Designing scalable pipelines
Secure secret handling
Efficient build execution
Zero-downtime deployments
Enterprise-grade automation
This is core DevOps engineering knowledge.
✅ Day 20 Summary
Today I learned:
What CI/CD is and why it matters
Typical CI/CD pipeline stages
Comparison of Jenkins, GitHub Actions & GitLab CI
Jenkins Master–Agent architecture
Job types in Jenkins
Core Jenkins configuration areas
This lays the foundation for real pipeline implementation and automation.
➡️ Coming Next:
Hands-on demos of:
Freestyle Jobs
Pipeline Jobs
Multibranch Pipelines in Jenkins
