Lab 5: Install Docker and verify the engine

Objective

Install Docker Engine from the official apt repository on a fresh Ubuntu 24.04 LTS host. Verify the install end-to-end. Pin the major version so subsequent apt upgrade calls do not surprise you.

Requirements

• Ubuntu 24.04 LTS (or 22.04 LTS) host, freshly installed.
• sudo access.
• Outbound HTTPS to download.docker.com.
• A non-root user you can add to the docker group, or sudo for every docker invocation.

Tasks

Task 1: Add Docker’s official GPG key

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

Task 2: Add the repository

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
sudo apt-get update

Task 3: Install pinned version

# List available versions
apt-cache madison docker-ce | head -5

# Install a specific version (example: 28.1.1)
sudo apt-get install -y \
  docker-ce=5:28.1.1-1~ubuntu.24.04~noble \
  docker-ce-cli=5:28.1.1-1~ubuntu.24.04~noble \
  containerd.io \
  docker-buildx-plugin \
  docker-compose-plugin

Task 4: Pin the major version

sudo apt-mark hold docker-ce docker-ce-cli

Task 5: Enable and start the daemon

sudo systemctl enable --now docker
sudo systemctl status docker

Task 6: Verify

docker version
docker info
sudo docker run --rm hello-world

Task 7: Non-root user

sudo usermod -aG docker $USER
# log out and back in
docker ps

Expected outcome

• docker version shows Server Version 28.x.
• docker info lists the storage driver, cgroup driver, and kernel version.
• hello-world prints its standard success message.
• The user can run docker ps without sudo.

Cleanup

Nothing to clean up. The hello-world container is --rm and exits immediately.