Configuring Docker on VPS for Application Deployment: A Complete Guide

In today’s fast-paced software development environment, containerization has become a game-changer. Docker, one of the most popular containerization platforms, simplifies the deployment, scaling, and management of applications. By running applications in isolated environments called containers, Docker helps developers achieve consistency, speed, and flexibility, regardless of the system they're working on.

One of the best ways to leverage Docker is by setting it up on a Virtual Private Server (เช่า VPS). This allows you to host, manage, and deploy applications in a controlled, efficient, and scalable environment. In this guide, we’ll walk you through configuring Docker on a VPS to streamline your application deployment process.

What is Docker and Why Use It on a VPS?
Docker is an open-source platform that automates the deployment and scaling of applications within lightweight, portable containers. These containers contain all the dependencies needed to run an application, ensuring that it will run consistently across different environments.

Benefits of Using Docker on VPS:
Portability: Docker containers can run on any VPS regardless of the underlying operating system.
Isolation: Containers isolate your application, reducing conflicts between different software versions or dependencies.
Efficiency: Docker allows for better resource management since it only uses the resources it needs, compared to traditional virtual machines.
Scalability: Easily scale your application by running multiple containers across a single VPS or multiple VPS instances.

Step 1: Setting Up Docker on Your VPS
Before you can deploy your applications with Docker, you need to install Docker on your VPS. Let’s break this down for popular Linux distributions.

1. Installing Docker on Ubuntu/Debian
Update the System:

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sudo apt update
sudo apt upgrade -y
Install Docker:

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sudo apt install apt-transport-https ca-certificates curl software-properties-common -y
Add Docker’s Official GPG Key:

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curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Set Up the Docker Repository:

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sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
Install Docker Engine:

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sudo apt update
sudo apt install docker-ce -y
Verify the Installation:

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sudo docker --version
2. Installing Docker on CentOS/RHEL
Update the System:

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sudo yum update -y
Install Docker:

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sudo yum install -y yum-utils device-mapper-persistent-data lvm2
Add Docker Repository:

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sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
Install Docker:

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sudo yum install docker-ce -y
Start Docker:

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sudo systemctl start docker
sudo systemctl enable docker
Verify the Installation:

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sudo docker --version

Step 2: Configuring Docker on Your VPS
Once Docker is installed, you'll need to configure it to ensure optimal performance and security for your application deployment.

1. Manage Docker as a Non-Root User
By default, Docker requires root privileges. However, you can run Docker commands as a non-root user to enhance security.

Create a Docker Group:

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sudo groupadd docker
Add Your User to the Docker Group:

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sudo usermod -aG docker $USER
Log out and log back in, then verify by running:

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docker run hello-world

2. Adjust Docker’s Configuration File
Docker’s configuration file allows you to customize the default behavior. You can edit it to configure the storage driver, logging, and more.

Edit Docker Daemon Configuration:

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sudo nano /etc/docker/daemon.json
Example Configuration: To set Docker to use a specific storage driver, you can add:

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{
  "storage-driver": "overlay2",
  "log-driver": "json-file"
}
Restart Docker to apply changes:

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sudo systemctl restart docker

Step 3: Docker Networking Setup
Docker allows for various types of networks for containers to communicate with each other and the outside world. The default network is bridge, but there are several others, such as host and overlay, depending on your application needs.

1. List Available Networks:
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docker network ls

2. Create a Custom Network:
If you want to create a custom network for your application, use:

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docker network create --driver bridge my_network

3. Attach Containers to the Network:
When running a container, you can specify the network:

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docker run --network my_network -d my_image
This setup ensures containers are properly isolated and can communicate securely with each other.

Step 4: Deploying Your Application with Docker
Now that Docker is set up and configured, it’s time to deploy your application. Let’s deploy a sample web application using Docker.

1. Create a Dockerfile for Your Application
A Dockerfile is a script that contains all the commands to assemble your Docker image. Here’s an example for a simple Node.js app:

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# Use Node.js as the base image
FROM node:14

# Set the working directory in the container
WORKDIR /app

# Copy the package.json and install dependencies
COPY package.json .
RUN npm install

# Copy the rest of the application files
COPY . .

# Expose the application port
EXPOSE 3000

# Run the application
CMD ["npm", "start"]

2. Build Your Docker Image:
Navigate to the directory containing your Dockerfile and build the image:

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docker build -t my_node_app .

3. Run Your Application in a Container:
Once the image is built, you can run it:

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docker run -d -p 80:3000 my_node_app
This runs the application in the background and maps port 80 on the VPS to port 3000 in the container.

Step 5: Scaling Your Application with Docker
One of the key benefits of Docker is scalability. You can run multiple instances of your application to handle high traffic.

1. Run Multiple Containers:
To scale your application, run multiple containers using the following command:

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docker run -d -p 80:3000 --name my_app_instance_1 my_node_app
docker run -d -p 81:3000 --name my_app_instance_2 my_node_app

2. Use Docker Compose for Multi-container Applications:
Docker Compose simplifies the management of multi-container applications. Here’s an example docker-compose.yml file:

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version: '3'
services:
  web:
    build: .
    ports:
      - "80:3000"
  db:
    image: postgres:alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
To start the application, run:

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docker-compose up -d

Step 6: Monitoring Docker Containers
To ensure your application runs smoothly, monitoring Docker containers is essential.

1. View Running Containers:
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docker ps

2. Check Logs:
To view the logs of a specific container:

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docker logs my_app_instance_1

3. Monitor Resource Usage:
Docker provides a simple command to monitor the resources used by containers:

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docker stats