---
title: 'Dockerfile: A Complete Guide for Beginners and Professionals | Zomro'
description: 'Understanding Dockerfile and knowing how to use it correctly is essential for effective use of Docker.'
image: 'https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/dalle-2024-07-08-210308-a-minimalist-rectangular-widescreen-infographic-in-pink-and-purple-colors-themed-around-dockerfile_-complete-guide-for-beginners-and-professionals_q50.jpg'
---

![opened image]()

  * [Zomro](https://zomro.com/)
  * [FAQ](https://zomro.com/blog/faq/)
  * Dockerfile: A Complete Guide for Beginners and Professionals 



# Dockerfile: A Complete Guide for Beginners and Professionals

08-07-2024

![Dockerfile: A Complete Guide for Beginners and Professionals - 1](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/dalle-2024-07-08-210308-a-minimalist-rectangular-widescreen-infographic-in-pink-and-purple-colors-themed-around-dockerfile_-complete-guide-for-beginners-and-professionals_q50.jpg)

**Docker** — is a powerful tool for creating, deploying, and managing containers that has become the de facto standard in the software development industry. One of the key elements of **Docker** is the **Dockerfile** — a text file containing instructions for building a **Docker** image. Understanding Dockerfile and knowing how to use it correctly is essential for effective use of **Docker**.

**What is a Dockerfile?**  


**Dockerfile** — is a script that contains a set of commands and instructions for creating a **Docker image**. A **Docker image** , in turn, is an immutable template that includes everything needed to run a container: the operating system, libraries, dependencies, and the application itself.

**Basic Dockerfile Instructions**  


First, let's look at the basic instructions used in a **Dockerfile** :

**FROM:** This instruction sets the base image on which the new image will be built. For example, **FROM ubuntu:20.04** indicates that the base image will be **Ubuntu 20.04**.

**RUN:** Used to execute commands in the container. Typically used for installing packages and performing other operations necessary to prepare the environment.

**CMD:** Defines the command that will be executed when the container starts. Unlike **RUN** , this command is not executed during the image build, but only when the container is run.

**ENTRYPOINT:** Allows you to specify a command that will always be executed when the container starts. It can be overridden when starting the container with command-line parameters.

**COPY and ADD** : These instructions are used to copy files and directories from the local file system to the image's file system. **COPY** performs a simple copy, while **ADD** can additionally unpack files and download them via **URL**.

**ENV:** Sets environment variables inside the container.

**EXPOSE:** Indicates which ports will be open in the container for external access.

**VOLUME:** Creates a mount point for working with persistent storage.

**WORKDIR:** Sets the working directory for all subsequent instructions.

**Example Dockerfile**

Let's consider a simple example of a **Dockerfile** for a **Node.js** application:
    
    
    # Specify the base image
    FROM node:14
    
    # Set the working directory
    WORKDIR /app
    
    # Copy package.json and package-lock.json
    COPY package*.json ./
    
    # Install dependencies
    RUN npm install
    
    # Copy the application source code
    COPY . .
    
    # Specify the port
    EXPOSE 3000
    
    # Define the command to run the application
    CMD ["npm", "start"]
    

![Dockerfile: A Complete Guide for Beginners and Professionals - 2](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/01_frpnJ5V_q50.jpg)

  
**Detailed Breakdown of Dockerfile:**

**​​​​​​​**

**FROM node:14** — Indicates that the base image will be the official **Node.js** image version **14**. This means that all necessary dependencies for **Node.js** will be included in our image.

**WORKDIR /app** — Sets the working directory **/app** , where files will be copied and commands will be executed.

**COPY package.json ./*** — Copies the **package.json** and **package-lock.json** files into the container's working directory. These files contain information about the application's dependencies.

**RUN npm install** — Executes the installation of dependencies specified in package.json.

**COPY . .** — Copies all files and folders from the current directory (where the **Dockerfile** is located) into the container's working directory.

**EXPOSE 3000** — Indicates that the container will listen on port **3000**.

**CMD ["node", "app.js"]** — Defines the command to run the application. In this case, it is running the **app.js** file using **Node.js**.

  


Create a file **app.js** with the following content, or use your own:  
  
  

    
    
    // app.js
    
    const express = require('express');
    const app = express();
    const port = 3000;
    
    app.get('/', (req, res) => {
      res.send('Hello, World!');
    });
    
    app.listen(port, () => {
      console.log(`Server is running on http://localhost:${port}`);
    });

  
Create a file **package.json** with the following content:
    
    
    {
      "name": "my-node-app",
      "version": "1.0.0",
      "description": "A simple Node.js app with Express",
      "main": "app.js",
      "scripts": {
        "start": "node app.js"
      },
      "dependencies": {
        "express": "^4.17.1"
      }
    }

![Dockerfile: A Complete Guide for Beginners and Professionals - 3](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/011_q50.jpg)

**Using Dockerfile**

Now that we have reviewed the basic instructions and looked at an example **Dockerfile** , let's move on to practical use. To create a **Docker** image and run a container, you need to execute a few commands in the terminal.

Make sure that the **app.js** , **package.json** , and **Dockerfile** files are in the same directory. Then create the image.

**Creating the image:**
    
    
    docker build -t my-node-app .

Here, **-t my-node-app** sets the name of the image, and **.** indicates that the **Dockerfile** is located in the current directory.

![Dockerfile: A Complete Guide for Beginners and Professionals - 4](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/02_VwK1Dib_q50.jpg)

**Running the container:**
    
    
    docker run -p 3000:3000 my-node-app

The **docker run** command starts a container based on the created image. The **-p 3000:3000** parameter indicates that port **3000** on the host machine will be forwarded to port **3000** in the container. Your server should start successfully, and you will be able to access it by opening **http://localhost:3000** in your browser, where you will see the simple greeting **"Hello, World!"**.

![Dockerfile: A Complete Guide for Beginners and Professionals - 5](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/03_CRPsR7Y_q50.jpg)

![Dockerfile: A Complete Guide for Beginners and Professionals - 6](https://dx86q6oq7ry0e.cloudfront.net/uploads/blog/a48%40server-panel.net/2024/07/08/04_kxzdzml_q50.jpg)​​​​​​​

**Conclusion**

**Dockerfile** — is a powerful tool for automating and standardizing the process of creating **Docker images**. Understanding the basic instructions and principles of working with **Dockerfile** allows developers to effectively manage environments and deploy applications in containers. It is important to remember that a **Dockerfile** should be optimized and contain only the necessary commands to minimize the image size and improve container performance.

Similar articles:

[Installing the Pterodactyl Control Panel (Ubuntu)](https://zomro.com/blog/faq/358-installing-the-pterodactyl-control-panel-ubuntu) [How to install MySQL 8 in Docker](https://zomro.com/blog/faq/291-kak-ustanovit-mysql-8-v-docker) [Connecting to a Server via SSH](https://zomro.com/blog/faq/142-podkljuchenie-k-serveru-po-ssh) [How to install FileGator on Centos Nginx-PHP-FPM](https://zomro.com/blog/faq/381-how-to-install-filegator-on-centos-nginx-php-fpm-zomro) [Adding resource records to a domain in DNS hosting](https://zomro.com/blog/faq/296-dobavlenie-zapisej-v-dns-hosting)

[ Premium Cloud VPS from €7.95/mon ](/premium-vps)