Docker → run the web app inside a Docker container.

To run a web app inside a Docker container, follow these steps:

Create a Dockerfile:

This file contains instructions for building the Docker image. A basic Dockerfile for a web app might look like this:

            
            FROM <base_image>
            WORKDIR /app
            COPY . .
            RUN <install_dependencies_command>
            EXPOSE <port>
            CMD ["<command_to_start_app>"]

Replace <base_image> with a suitable base image (e.g., python:3.9, node:16).
<install_dependencies_command> installs the necessary packages (e.g., pip install -r requirements.txt, npm install).
<port> is the port your web app listens on.
<command_to_start_app> is the command to run your app (e.g., python app.py, npm start).

Build the Docker image: Navigate to the directory containing your Dockerfile and run:

docker build -t <image_name> .

Replace <image_name> with a name for your image.

Run the Docker container:

docker run -d -p <host_port>:<container_port> <image_name>

-d runs the container in detached mode (background).
-p maps the host port to the container port, allowing access from outside the container.

Replace <host_port> with the port you want to access the app on (e.g., 8080) and <container_port> with the port your app uses (defined in the Dockerfile, e.g., 5000).

Access the web app: Open a web browser and go to http://localhost:<host_port>.

Verify the container is running:

docker ps

Stop the container:

docker stop <container_id or container_name>

Remove the container:

docker rm <container_id or container_name>

How to Confirm the File Path Inside a Docker Container

You can get inside your container and explore the file structure:

docker exec -it <your_container_name> bash

Once inside the container:

cd /usr/src/app
ls

This helps you confirm where index.html should live.

✅ Best Practice: Rebuild and Restart Container

If your change (like editing index.html) is meant to be permanent or version-controlled:

docker build -t <image_name> .

docker stop <container_name_or_id>

docker rm <container_name_or_id>

docker run -d -p 8080:80 --name <new_container_name> <image_name>

🧪 Quick and Dirty: Copy File into Running Container

Hint: /usr/src/app is a common convention in Linux, particularly when working with containers and Dockerfiles, to indicate the working directory for an application. It's a good location as it follows the Linux File System Hierarchy Standard (FHS), where /usr/src is traditionally used for source code

For fast, temporary changes:

docker cp index.html <container_name_or_id>:/path/to/index.html

You might need to restart the service inside the container depending on your setup (e.g., Nginx or Node.js).

🧰 Dev-Friendly: Use Volume Mounting

For live development:

docker run -d -p 8080:80 \
  -v "$(pwd)/your-folder:/usr/share/nginx/html" \
  --name dev_container nginx

This syncs your local folder with the container’s web root, so file changes are reflected instantly.

Summary

Method	Use Case	Command Needed After Change?
Rebuild & Restart	Production, permanent	Yes: build, run
docker cp	Quick patch	Only `docker cp`
Volume mount	Active development	No, auto-updates