How to Install & Set Up Docker Engine

Prerequisites

• ✓A 64-bit Ubuntu/Debian host (or another supported Linux distribution) — Docker Desktop covers macOS/Windows separately
• ✓sudo privileges; remove any distro-packaged docker.io or podman-docker package first to avoid conflicts
• ✓A few hundred MB of free disk under /var/lib/docker — images and layers live there by default

Images, containers, and the daemon — the mental model

An image is a read-only, layered filesystem plus metadata (entrypoint, exposed ports, env defaults) — think of it as a class. A container is a running (or stopped) instance of that image with its own writable layer on top — think of it as an object. Every docker run creates a new container from an existing image without ever modifying the image itself.

Under the hood, the docker CLI talks to the dockerd daemon over a local socket; dockerd delegates the actual container lifecycle to containerd, which in turn uses runc to do the low-level OS work (namespaces, cgroups) that actually isolates the process. You install all three together — the docker-ce, docker-ce-cli, and containerd.io packages below — because they're one release train.

Add Docker's official APT repository

sudo apt-get update
sudo apt-get install -y ca-certificates curl
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
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
sudo apt-get update

Install the Docker packages

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

Install on RHEL, CentOS Stream, or Fedora (official RPM repo)

Same package set, same daemon, just swap the repo URL's distro segment (centos, fedora, rhel) to match your host.

sudo dnf -y install dnf-plugins-core
sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
sudo dnf install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo systemctl enable --now docker

Run Docker without sudo (optional)

sudo usermod -aG docker $USER
newgrp docker

Verify the installation

docker --version
docker run hello-world

Build and run your own image

Pulling someone else's image is only half the picture — the other half is writing a Dockerfile that describes how to build yours. Each instruction adds a cached layer, so ordering matters: put the things that change least often (installing dependencies) before the things that change most often (your source code) to keep rebuilds fast.

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY . .
EXPOSE 3000
CMD ["node", "server.js"]

docker build -t my-app:latest .
docker run -d --name my-app -p 3000:3000 my-app:latest
docker ps
docker logs -f my-app

Networking basics

• •bridge (default) — every container gets a private IP on a virtual bridge network; -p HOST:CONTAINER publishes a port to the host so the outside world can reach it.
• •host — the container shares the host's network namespace directly (no port mapping needed, but no isolation either); Linux-only.
• •none — no networking at all, for fully isolated jobs.
• •docker network create mynet plus --network mynet lets multiple containers reach each other by container name — the basis for anything multi-service before you reach for Compose.

Persisting data with volumes

A container's writable layer disappears the moment you docker rm it, so anything that needs to survive — a database's data directory, uploaded files — belongs in a volume, not the container filesystem.

docker volume create app-data
docker run -d -v app-data:/var/lib/data my-app:latest

docker run -d -v "$(pwd)/data:/var/lib/data" my-app:latest

Running multiple services with Compose

Once an app is more than one container — say a web service plus a database — Docker Compose lets you describe the whole stack in one YAML file and bring it up or down as a unit.

services:
  web:
    build: .
    ports: ["3000:3000"]
    depends_on: [db]
  db:
    image: postgres:16
    environment:
      POSTGRES_PASSWORD: example
    volumes: ["db-data:/var/lib/postgresql/data"]
volumes:
  db-data:

docker compose up -d
docker compose down

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