Containerization_and_DevOpsLab

Lab Report: Lab-3 Part-2

Dockerfile Based Flask Web App Containerization

Date: 07/02/2026
Author: Divyanshu Gaur
SAP ID: 500121752

1. Objective

The objective of this lab is to:

Create a Flask web application
Run the Flask app locally without Docker
Define dependencies using requirements.txt
Create a Dockerfile for the Flask app
Pull Python base image
Run Flask inside Docker container
Verify container deployment on localhost
Stop and remove containers

2. Procedure and Results

Step 1: Create Flask Project Structure

A Flask project directory was created with application file, requirements file, and Dockerfile.

Execution Screenshot: Project Structure

Step 2: Write Flask Application Code

The Flask application was written with a root route serving an HTML page containing lab details.

Execution Screenshot: Flask App Code

Step 3: Create Requirements File

The dependency file was created specifying Flask version.

Execution Screenshot: Requirements File

Step 4: Create Dockerfile

A Dockerfile was created using Python 3.9 slim image with working directory, copy steps, dependency installation, port exposure, and run command.

Execution Screenshot: Dockerfile

Step 5: Run Flask App Without Docker

The Flask app was executed directly on the host system.

Command:
python app.py

Execution Screenshot: Local Flask Run

Step 6: Verify Localhost Output (Without Docker)

The application output was verified in the browser and using curl.

Execution Screenshot: Localhost Output

Step 7: Pull Python Base Docker Image

Python slim image was pulled from Docker Hub.

Command:
docker pull python:3.9-slim

Execution Screenshot: Docker Pull

Step 8: Run Interactive Docker Container and Install Flask

A container was started and Flask was installed inside it. The application was created and executed inside the container.

Command:
docker run -it --name flask-container python:3.9-slim /bin/bash

Execution Screenshot: Container Setup

Step 9: Verify Running Containers

Running containers were checked using docker ps.

Command:
docker ps

Execution Screenshot: Docker PS

Step 10: Access Flask App from Container

The Flask app running inside the container was accessed through localhost port mapping.

Execution Screenshot: Container Localhost

Step 11: Stop Running Container and Remove Container

The running container was stopped and was removed from the system.

Command:
docker stop flask-container docker rm flask-container

Execution Screenshot: Docker Stop

3. Result and Conclusion

Result

The Flask web application was successfully:

Developed and executed locally
Containerized using Docker
Executed inside a Python Docker container
Accessed through localhost
Managed using Docker lifecycle commands

Conclusion

This experiment demonstrated Docker-based containerization of a Flask web application. It validated portability, environment consistency, and simplified deployment using containers.