GUIDEServer Management

Installing Docker & Docker Compose

5 min read

Docker is a platform for building, shipping, and running applications in containers — lightweight, portable environments that include everything your application needs. Docker Compose extends Docker by letting you define and run multi-container applications with a single configuration file. This guide shows you how to install both on your Data Mammoth VPS.

Prerequisites

A Data Mammoth VPS running Ubuntu 22.04/24.04, Debian 12, or CentOS/AlmaLinux.
SSH access with sudo privileges.
At least 1 GB of RAM (2 GB or more recommended for production workloads).

Installing Docker on Ubuntu / Debian

Step 1 — Remove Old Versions

Remove any previously installed Docker packages:

sudo apt remove docker docker-engine docker.io containerd runc 2>/dev/null

Step 2 — Install Prerequisites

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

Step 3 — Add Docker's Official GPG Key and Repository

sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

Add the repository (for Ubuntu):

echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

For Debian, replace ubuntu with debian in the URL above.

Step 4 — Install Docker Engine

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

Step 5 — Verify the Installation

sudo docker run hello-world

You should see a message confirming Docker is installed correctly.

Installing Docker on CentOS / AlmaLinux

Step 1 — Remove Old Versions

sudo dnf remove docker docker-client docker-client-latest docker-common docker-latest docker-latest-logrotate docker-logrotate docker-engine 2>/dev/null

Step 2 — Add Docker Repository

sudo dnf install -y dnf-plugins-core
sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Step 3 — Install Docker Engine

sudo dnf install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 4 — Start and Enable Docker

sudo systemctl start docker
sudo systemctl enable docker

Step 5 — Verify

sudo docker run hello-world

Post-Installation Setup

Run Docker Without Sudo

By default, Docker commands require sudo. To run Docker as a non-root user, add your user to the docker group:

sudo usermod -aG docker $USER

Log out and log back in for the change to take effect. Verify:

docker run hello-world

Security note: Adding a user to the docker group grants root-equivalent privileges through Docker. Only add trusted users.

Configure Docker to Start on Boot

Docker should start automatically on boot by default, but verify:

sudo systemctl enable docker
sudo systemctl enable containerd

Using Docker Compose

Docker Compose is now included as a Docker plugin (no separate installation needed). Use the docker compose command (with a space, not a hyphen):

docker compose version

Creating a Docker Compose File

Create a project directory and a docker-compose.yml file:

mkdir ~/myapp && cd ~/myapp
nano docker-compose.yml

Example — a simple web application with a database:

version: '3.8' services: web: image: nginx:latest ports: - "80:80" volumes: - ./html:/usr/share/nginx/html depends_on: - db restart: unless-stopped db: image: mysql:8.0 environment: MYSQL_ROOT_PASSWORD: your_secure_password MYSQL_DATABASE: myapp MYSQL_USER: appuser MYSQL_PASSWORD: your_app_password volumes: - db_data:/var/lib/mysql restart: unless-stopped

volumes: db_data:

Basic Docker Compose Commands

# Start all services in the background
docker compose up -d
View running containers
docker compose ps
View logs
docker compose logs -f
Stop all services
docker compose down
Rebuild and restart
docker compose up -d --build
Stop and remove volumes (deletes data)
docker compose down -v

Essential Docker Commands

# List running containers
docker ps
List all containers (including stopped)
docker ps -a
View container logs
docker logs <container_name>
Execute a command inside a container
docker exec -it <container_name> bash
Pull an image
docker pull nginx:latest
Remove stopped containers
docker container prune
Remove unused images
docker image prune
View disk usage
docker system df
Clean up everything unused
docker system prune -a

Docker Storage and Disk Management

Docker images, containers, and volumes can consume significant disk space. Monitor usage with:

docker system df

To free up space:

# Remove stopped containers
docker container prune -f
Remove unused images
docker image prune -a -f
Remove unused volumes (careful — this deletes data)
docker volume prune -f

Schedule regular cleanups if you frequently build and deploy containers.

Docker Networking

Docker creates its own network bridge by default. Containers on the same Docker Compose project can communicate using service names as hostnames.

# List Docker networks
docker network ls
Inspect a network
docker network inspect bridge

Security Best Practices

Keep Docker updated — Regularly update Docker to get security patches.

Use official images — Pull images from trusted sources on Docker Hub.

Do not run containers as root — Use the USER directive in Dockerfiles.

Limit container resources — Set memory and CPU limits in Docker Compose:

services:
  web:
    image: nginx
    deploy:
      resources:
        limits:
          cpus: '0.5'
          memory: 512M

Do not expose unnecessary ports — Only map the ports your application needs.

Use Docker secrets — Avoid putting passwords directly in compose files for production use.

Firewall Configuration for Docker

Docker modifies iptables rules directly, which can bypass UFW or firewalld. To prevent Docker from exposing ports unintentionally:

sudo nano /etc/docker/daemon.json

Add:

{
  "iptables": false
}

Restart Docker:

sudo systemctl restart docker

Then manually manage port access through your firewall. See Server Firewall Hardening Guide.

What to Do Next

Installing n8n from the Marketplace — Deploy n8n with Docker.
How to Install an App on Your Server — Install marketplace apps.
Backup Strategy — Snapshots, Offsite, Automated — Back up your Docker volumes.
Monitoring Server Performance — Monitor container resource usage.

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