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What is Docker and Docker Compose?

Docker

Docker is an open-source platform that enables you to automate the deployment, scaling, and management of applications inside lightweight, portable containers. Containers isolate your applications from the host system, making them portable and consistent across different environments. Unlike virtual machines, containers share the host OS kernel, which makes them more resource-efficient.

Docker is ideal for running single services or applications in isolated environments and provides all the necessary commands to build, run, and manage containers.

Docker Compose

Docker Compose is a tool for defining and managing multi-container Docker applications. With Docker Compose, you define your application’s services, networks, and volumes in a single YAML file (typically called docker-compose.yml). Compose allows you to start, stop, and manage multiple containers as a single application with just one command. It is especially useful for applications consisting of several interdependent services (like a web server, database, and cache).

Key differences:

Docker is best for running and managing single containers.

Docker Compose is designed to organize and manage multiple containers together as one application stack, handling configuration and network setup automatically.

Installing Docker & Docker Compose

Below are the installation steps for Docker and Docker Compose on Debian and Ubuntu.

Install Docker & Docker Compose on Debian

# Update package lists and install dependencies
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg lsb-release

# Add Docker’s official GPG key
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

# Add Docker’s repository to Apt sources
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian \
  $(. /etc/os-release && echo \"$VERSION_CODENAME\") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# Install Docker Engine and Docker Compose (v2 is now included as a plugin)
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

# Enable and start Docker service
sudo systemctl enable --now docker
sudo service docker start

Install Docker & Docker Compose on Ubuntu

# Update package lists and install dependencies
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg lsb-release

# Add Docker’s official GPG key
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

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

# Install Docker Engine and Docker Compose (v2 as plugin)
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

# Enable and start Docker service
sudo systemctl enable --now docker
sudo service docker start

Linux Post-Installation Steps for Docker

These optional steps help configure your Linux system for easier Docker usage.

Run Docker Without sudo

By default, Docker requires sudo because the Docker daemon runs as root and listens on a Unix socket owned by root.

To allow your user to run Docker without sudo:

# 1. Create the docker group (skip if it already exists)
sudo groupadd docker

# 2. Add your user to the docker group
sudo usermod -aG docker $USER

# 3. Apply changes
newgrp docker

References