====== Systems - Docker Main - Install Docker ======

===== Install Dependencies =====

Install dependencies necessary to add a new HTTPS repository.

<code bash>
sudo apt install apt-transport-https ca-certificates curl gnupg-agent software-properties-common
</code>

----

===== Import the Docker GPG Key =====

<code bash>
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
</code>

----

===== Add the Docker apt Repository =====

<code bash>
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
</code>

----

===== Install Docker =====

<code bash>
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io
</code>

<WRAP info>
**NOTE:** This will install the latest version of Docker.

  * The Docker service will start automatically after the install.

  * To install a specific version of Docker, list available versions: <code bash>
sudo apt update
apt list -a docker-ce
</code>

  * and install with: <code bash>
sudo apt install docker-ce=<VERSION> docker-ce-cli=<VERSION> containerd.io
</code>
</WRAP>

<WRAP info>
**NOTE:**  Docker will be automatically updated through standard: <code bash>
sudo apt update
sudo apt upgrade
</code>

  * To prevent the Docker package from being updated, mark it as held back: <code bash>
sudo apt-mark hold docker-ce
</code>
</WRAP>

----

===== Check the Docker Status =====

<code bash>
sudo systemctl status docker
</code>

----

===== Set Permissions =====

Non-Root User

<code bash>
sudo usermod -aG docker $USER
</code>

<WRAP info>
**NOTE:**  By default, only root and user with sudo privileges can execute Docker commands.

  * **$USER** is an environment variable that holds the logged in username.

  * Log out and log back in so that the group membership is refreshed.
</WRAP>

----

===== Verifying the Docker Installation =====

<code bash>
docker container run hello-world
</code>

<WRAP info>
**NOTE:**  This should display **Hello from Docker**.
</WRAP>