Using Docker

Introduction to Docker

Docker is a platform designed to make it easier to create, deploy, and run applications by using containers. Containers allow a developer to package up an application with all parts it needs, such as libraries and other dependencies, and ship it all out as one package.

Installing Docker

Before you can use Docker, you need to install it on your system. Here’s a step-by-step guide for installing Docker on a Linux system.

After the installation, you can verify that Docker is installed correctly by running the following command:

Running Your First Docker Container

Once Docker is installed and running, you can start your first container. We'll use the official Docker image for "hello-world" to verify that Docker is working correctly.

Creating a Dockerfile

A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build, users can create an automated build that executes several command-line instructions in succession.

Here is an example of a simple Dockerfile:

# Use an official Python runtime as a parent image
FROM python:3.8-slim

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World

# Run app.py when the container launches
CMD ["python", "app.py"]
                

Building and Running Your Docker Image

Once you have created a Dockerfile, you can build an image from it:

After the image is built, you can run it as a container:

This command maps port 4000 on your host to port 80 in the container. You should now be able to access the application by navigating to http://localhost:4000 in your web browser.

Managing Docker Containers

You can list all running containers using:

To list all containers (running and stopped):

To stop a running container:

To remove a stopped container:

To remove an image:

Conclusion

Docker is a powerful tool for developing, shipping, and running applications inside containers. This tutorial covered the basics of installing Docker, running your first container, creating Dockerfiles, building and running images, and managing containers. With these basics, you can start exploring more advanced Docker features and workflows to streamline your development and deployment processes.