Docker on VPS: A Beginner's Guide to Containerizing Your First App

If you have recently subscribed to a Virtual Private Server (VPS) and are looking to deploy applications efficiently, you have likely heard the buzz surrounding containerization. But what does it actually mean for your VPS hosting setup? This guide is designed to take you from a complete novice to a confident user capable of containerizing and running your first application on a live VPS server.

What is Docker and Why Should VPS Users Care?

Docker is an open-source platform that automates the deployment of applications inside lightweight, portable containers. Think of a shipping container: it doesn't matter what is inside (furniture, cars, electronics), the shipping infrastructure handles it exactly the same way.

Docker does this for code on your VPS hosting environment. It wraps your application and all its dependencies—libraries, runtime, system tools—into a single package. This guarantees that your application will run exactly the same way on your virtual private server as it does on your laptop, eliminating environment-specific bugs that often plague traditional server hosting setups.

The Perfect Pair: Docker and VPS Hosting

A VPS gives you a slice of a physical server with its own dedicated resources. When you combine this with Docker, you gain incredible flexibility for your hosting environment. You aren't limited to running just one type of software. You can run a Python app, a Node.js server, and a MySQL database side-by-side in isolated containers without them conflicting with each other. It is the cleanest, most efficient way to utilize your VPS server resources.

Benefits of Docker on VPS Hosting

Resource Efficiency: Containers share the host OS kernel, using less memory than traditional virtual machines
Consistent Deployments: Your app runs identically across development and production VPS environments
Scalability: Easily scale your applications on your VPS hosting plan
Isolation: Each container runs independently, improving server security
Fast Deployment: Spin up new instances in seconds on your virtual private server

Prerequisites: Setting Up Your VPS Environment

Before we dive into the commands, we need to ensure the foundation is solid for your VPS hosting setup.

Choosing a VPS Hosting Provider

To follow along, you need a VPS running a Linux operating system. Ubuntu 20.04 LTS or 22.04 LTS is highly recommended for beginners due to its vast community support and ease of use. Ready Server's VPS hosting plans offer affordable entry-level virtual private servers that are perfect for this tutorial, with instant deployment and full root access.

Accessing Your VPS Server via SSH

You will need to interact with your VPS using the command line. Open your terminal (or Command Prompt/PowerShell on Windows) and log in to your server:

ssh root@your_server_ip

Replace your_server_ip with the actual IP address of your VPS. Once you are in, you are ready to start configuring your hosting environment.

Step 1: Installing Docker on Your Linux VPS

Most Linux distributions do not come with Docker pre-installed on your VPS hosting environment. Let's fix that. We will use the official Docker repository to ensure we get the latest version.

Updating Your VPS System Packages

First, refresh your package index to ensure you are not installing outdated software on your virtual private server:

sudo apt-get update
sudo apt-get upgrade -y

Setting Up the Docker Repository

Next, install a few prerequisite packages that allow apt to use packages over HTTPS on your VPS:

sudo apt-get install ca-certificates curl gnupg lsb-release -y

Now, add Docker's official GPG key (a security feature to verify the software):

sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

Installing the Docker Engine on Your VPS

With the repository set up, you can now install the Docker Engine, CLI, and Containerd on your VPS server:

sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin -y

To verify that Docker is installed and running correctly on your VPS hosting environment, run the following command. It should show you the current status as "active (running)":

sudo systemctl status docker

Step 2: Understanding Docker Core Concepts for VPS Hosting

Before we build anything on your virtual private server, we must distinguish between the two most important terms in the Docker ecosystem: Images and Containers.

Images vs. Containers: What's the Difference?

The Image: Think of this as a blueprint or a recipe for your VPS deployment. It is a read-only template that contains instructions for creating a container. It includes your code, libraries, and dependencies.

The Container: This is the running instance of the image on your VPS. If the image is the recipe, the container is the cake you baked. You can start, stop, move, and delete containers on your hosting server.

The Role of the Dockerfile

How do you create an image for your VPS hosting environment? You use a text file called a Dockerfile. This file contains a list of commands that the Docker client calls while building an image. It tells Docker exactly how to assemble your application for deployment on your virtual private server.

Step 3: Creating Your First Application on VPS

Let's containerize a very simple web server on your VPS. We will use Python for this example because it is easy to read, but the logic applies to any language you want to host.

Writing a "Hello World" Python Script

First, create a directory for your project on your VPS server and navigate into it:

mkdir my-first-docker-app
cd my-first-docker-app

Now, create a file named app.py:

nano app.py

Paste the following Python code inside. This creates a tiny web server that listens on port 8000 on your VPS:

from http.server import HTTPServer, BaseHTTPRequestHandler

class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.end_headers()
        self.wfile.write(b'Hello, World! You are running inside Docker on your VPS!')

httpd = HTTPServer(('0.0.0.0', 8000), SimpleHTTPRequestHandler)
print("Server running on port 8000...")
httpd.serve_forever()

Save and exit (Ctrl + X, then Y, then Enter).

Drafting Your First Dockerfile for VPS Deployment

Now, create a file simply named Dockerfile (no extension) for your VPS hosting deployment:

nano Dockerfile

Add the following content:

# Use an official Python runtime as a parent image
FROM python:3.9-slim

# Set the working directory inside the container
WORKDIR /app

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

# Make port 8000 available to the world outside this container
EXPOSE 8000

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

This file tells Docker to download Python, set up a folder, copy your script into it, and run the script on your VPS server.

Step 4: Building and Running Your Container on VPS

Now comes the magic. We will turn that text file into a running application on your VPS hosting environment.

Building the Docker Image

Run the following command to build your image on your VPS. The -t flag lets you tag your image with a name (we'll call it my-python-app). Note the dot . at the end—it tells Docker to look for the Dockerfile in the current directory:

docker build -t my-python-app .

Docker will download the necessary layers to your virtual private server. Once it finishes, your image is ready for deployment.

Running the Container on Your VPS Server

Now, let's run the container on your VPS. We will use the -d flag to run it in "detached" mode (in the background) so it doesn't block your terminal.

Port Mapping: Making Your App Accessible on VPS

This is crucial for your VPS hosting setup. Your app runs on port 8000 inside the container, but that port is closed to the outside world. We must map the VPS port to the container port:

docker run -d -p 80:8000 my-python-app

Here, -p 80:8000 tells Docker: "Take traffic coming into port 80 (standard web traffic) on my VPS, and send it to port 8000 inside the container."

Now, open your web browser and type your VPS IP address. You should see: "Hello, World! You are running inside Docker on your VPS!"

Step 5: Managing Docker Containers on Your VPS

You have a running container on your VPS hosting environment, but how do you control it?

Monitoring Running Containers

To see what is currently running on your VPS server, use:

docker ps

You will see a Container ID, the image name, and the status of each container on your virtual private server.

Stopping and Removing Containers

To stop a container on your VPS, use the Container ID (the first few characters are enough):

docker stop <container_id>

If you want to remove the container entirely from your VPS hosting environment (perhaps to deploy a new version), use:

docker rm <container_id>

Step 6: Data Persistence on VPS Hosting

One common pitfall for beginners using VPS hosting is assuming data saved inside a container lasts forever. It does not.

Understanding Ephemeral Filesystems

Containers are ephemeral on your VPS. If you delete a container and start a new one, any files created inside the previous container are lost. This is great for code updates but terrible for databases on your hosting server.

Using Docker Volumes for VPS Data Storage

To save data (like a database file or user uploads) on your VPS, you use Volumes. A volume is a directory on your virtual private server that is mounted into the container. Even if the container is destroyed, the data in the volume remains on your VPS hosting environment.

Example of running a container with a volume on your VPS:

docker run -d -p 80:8000 -v /my/vps/data:/app/data my-python-app

This maps the /my/vps/data folder on your VPS server to the /app/data folder inside the container.

Best Practices for VPS Security and Maintenance

Before you go, here are essential tips to keep your VPS hosting environment healthy and secure.

Avoiding the Root User on VPS

By default, Docker commands require root privileges (sudo) on your VPS. However, running applications inside the container as root can be a security risk. In production VPS hosting environments, you should configure your Dockerfile to switch to a non-root user after the setup steps.

Cleaning Up Unused Resources on Your VPS

Over time, old images and stopped containers take up storage space on your VPS server. Run this command occasionally to clean up your hosting system:

docker system prune

Warning: This deletes all stopped containers and unused networks from your VPS.

Regular VPS Maintenance Tips

Keep your VPS operating system updated with security patches
Monitor your server resources (CPU, RAM, storage) regularly
Set up automated backups for your Docker volumes
Use Docker Compose for managing multi-container applications on your VPS hosting setup

Conclusion: Your VPS Hosting Journey with Docker

Congratulations! You have successfully installed Docker on a VPS, written a Dockerfile, built an image, and deployed a live application on your virtual private server. You have moved past the "it works on my machine" dilemma and entered the world of professional VPS deployment.

Containerization might seem complex at first, but it ultimately simplifies how we manage software on VPS hosting environments. Your next steps should be exploring Docker Compose, which allows you to run multi-container applications (like a web server and a database) with a single command on your VPS server. The world of DevOps is vast, but you have just taken the most important first step.

Ready to get started with Docker on your own VPS? Check out our VPS hosting plans with instant deployment, full root access, and NVMe SSD storage to deploy your first containerized application today!