What is Docker and Why Should You Use It for Your Applications?

Docker is like a magic box for your applications! It helps you package everything your app needs – like the right operating system, files, and dependencies – into a neat, portable package. This way, your app stays happy and runs smoothly no matter where it goes, whether on your computer or somewhere else. It's like giving your app its own little world to live in!

Its like setting up your application on a new pc with your desired OS and stuff but its all automated and you just have to define it once.

Docker packages your application along with OS into smaller and portable virtual machine's like infrastructure called Docker Container.

Prerequisites:

• Docker, check out how you can install docker on Windows, Mac and Linux.

Create a Dockerfile

Create a Dockerfile in root directory of your project, Exact Dockerfile with no any file extension

Dockerfile is like a step by step script that tells Docker how it is going to build contianer image.

Go ahead and add the following code into your Dockerfile .

#node installation

FROM node:19-alpine

#working directory

WORKDIR /app

copy package.json into the working directory

COPY package*.json ./

#install all the dependencies of your project.

RUN npm install

#copy all the files from your current directory to the working directory of the container

COPY . .



#expose port 3000 from your container to local network

EXPOSE 3000

#start the development server from your container

CMD npm run dev

How to use .dockerignore and its importance

A .dockerignore is a configuration file that describes files and directories that you want to exclude when building a Docker image.

When you're building a Docker image for your application, the Dockerfile (which contains instructions on how to build the image) is usually placed in the root directory of your project. However, your project directory might contain various files that aren't necessary for your Docker image or that you don't want to include because they could make the image larger than it needs to be.

That's where the .dockerignore file comes in. It's a way to specify which files or directories should be excluded when building the Docker image. You list the files or patterns in the .dockerignore file, and Docker will make sure those are not included.

For example, if you have a Node.js project, you might have a .dockerignore file that looks like this:

node_modules


npm-debug.log

Creating your first Docker container

Let's build a home for our project using Docker! Open your command line, go to your project's main folder, and type 'docker build -t playerofcode .' This tells Docker to create a special container for our project named 'playerofcode'. You can pick any name you fancy. The dot at the end means the instructions for building this container are right here in our current folder.

docker build -t playerofcode .

Each time you will run this command, It will create a new image of your container, You can check what images are in your system by running docker images or docker image ls

Running docker container

 To run through command line, Open your terminal and run docker run -p 3000:3000 followed by the name and tag of your image

In my case:

docker run -p 3000:3000 playerofcode