I’ve started learning CI/CD (Continuous Integration and Continuous Deployment/Delivery) — a must-know process in modern DevOps for automating code building, testing, and deploying.

📌 What is CI/CD?

CI/CD stands for:

Continuous Integration (CI) – Automatically building and testing code every time a developer pushes code to the repo.
Continuous Deployment/Delivery (CD) – Automatically releasing code to production or staging after passing tests.

CI/CD helps in:
✅ Reducing manual work
✅ Detecting bugs early
✅ Faster and more reliable software delivery

🔧 Most Commonly Used CI/CD Tools

Tool	Description
Jenkins	Open-source automation server for building and deploying pipelines
GitHub Actions	CI/CD workflows built into GitHub repositories
GitLab CI/CD	Integrated with GitLab to run pipelines and deployments
CircleCI	Cloud-first CI/CD tool with container and Docker support
Travis CI	Easy integration with GitHub and open-source-friendly
Bitbucket Pipelines	Simple YAML-based CI/CD in Bitbucket environment
AWS CodePipeline	AWS-native CI/CD service for automated release pipelines

I’m first exploring Jenkins as my entry point into CI/CD tools.

It’s one of the most popular and flexible tools used for automating software build and deployment. Jenkins is an open-source automation server used to build, test, and deploy code continuously.

What I Learned About Jenkins

Main Components of Jenkins (Simplified)

1️⃣ Jenkins Master
- Central controller of Jenkins.
- Manages jobs, agents, plugins, and security.

2️⃣ Jenkins Agents

Workers that run build/test jobs.
Help distribute workload across machines.

3️⃣ Plugins

Add extra features to Jenkins.
Used for Git, build tools, notifications, reports, etc.

4️⃣ Jobs

Define tasks like build, test, deploy.
Configurable via UI or Jenkinsfile.

5️⃣ Pipeline

Scripted flow of CI/CD stages.
Written in code (Jenkinsfile) for versioning and flexibility.

My First 3 Jenkins Practice Tasks

1️⃣ Execute Shell Command Job

I created a simple freestyle project that runs shell commands to verify Jenkins is working as expected. This helped me understand how Jenkins executes scripts and displays output in the console.

2️⃣ Parameterized Job

In this task, I explored how to use input parameters in a Jenkins job. I set up a string parameter and used it dynamically within the shell execution step. This is useful when you want to pass custom values during build time.

3️⃣ Git Integration with Auto Trigger on Commit

Objective:
Connect Jenkins with GitHub and trigger job on every code update.
Trigger Used:
- Used Poll SCM to check for changes in the repo.
- It automatically pulls the latest code if a commit is detected.
Note for Production:
- In production, GitHub Webhooks are preferred (they trigger instantly).
  
  I used Poll SCM temporarily for learning purposes.
Cron Expression (Poll SCM):
- Jenkins uses cron syntax to define when polling should happen.
- * * * * * → runs the job every minute (used for testing).
- Learned how cron jobs work with time-based triggers.