Adding the Official Docker Repository

Follow these steps to configure the Apt package manager with Docker's official package source.

First, update the package index and install prerequisite utilities:

sudo apt update
sudo apt install ca-certificates curl

The ca-certificates package contains root certificaets for verifying secure HTTPS connections. The curl tool is used to transfer data from servers.

Create a directory to hold repository keyrings:

sudo install -m 0755 -d /etc/apt/keyrings

The install -m 0755 -d command creates a directory with read and execute permissions for all users.

Download Docker's public GPG key and save it to the keyrings directory:

sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc

The -fsSL flags make curl fail silently on errors, follow redirects, and suppress progress output.

Set appropriate read permissions on the key file:

sudo chmod a+r /etc/apt/keyrings/docker.asc

This grants read access to the key file for all user categories.

Add the Docker Apt repository to your system's sources list:

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

This command constructs a repository entry specifying the system architecture, GPG key location, and Ubuntu codename, then writes it to a dedicated sources file.

Update the package index again to include the new Docker repository:

sudo apt update

Installing Docker Packages

Install the Docker Engine and associated components:

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

Configuring Non-Root User Access

By default, Docker commands require sudo privileges. To allow a regular user to run Docker commands, add them to the docker group.

First, verify if the docker group exists:

grep docker /etc/group

If the group doesn't exist (which is rare with a standard installation), create it:

sudo groupadd docker

Add you're user to the docker group:

sudo usermod -aG docker $USER

Replace $USER with your actual username.

To activate the new group membership for your current session, log out and log back in, or run:

newgrp docker

Verifying the Installation

Check the installed Docker version to confirm successful setup:

docker version

This command displays both client and server version information if Docker is running correctly.