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====== Docker - Install Docker ======

===== Prerequisites =====

<WRAP alert>
**ALERT:**  Docker is only compatible with **iptables** and **ip6tables**.

  * Docker is NOT compatible with **ufw**.
  * See:  https://docs.docker.com/engine/network/packet-filtering-firewalls/

</WRAP>

----

===== Uninstall old versions =====

<code bash>
for pkg in docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc; do sudo apt remove $pkg; done
</code>

<WRAP info>
**NOTE:**  Images, containers, volumes, and networks stored in **/var/lib/docker/** are not automatically removed when you uninstall Docker.

  * To start with a clean installation, to clean up any existing data, read the [[https://docs.docker.com/engine/install/ubuntu/#uninstall-docker-engine|uninstall Docker Engine section]].

</WRAP>


To delete all images, containers, and volumes:

<code bash>
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd
</code>

Remove source list and keyrings

<code bash>
sudo rm /etc/apt/sources.list.d/docker.list
sudo rm /etc/apt/keyrings/docker.asc
</code>

<WRAP info>
**NOTE:**  Any edited configuration files will need to be deleted manually.
</WRAP>


----

===== Set up the Docker apt repository =====

<code bash>
# Add Docker's official GPG key:
sudo apt update
sudo apt install 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

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

----

===== Install the Docker packages =====

<code bash>
sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
</code>

<WRAP info>
**NOTE:**

  * **docker-ce** - The Docker engine itself.
  * **docker-ce-cli** - A command line tool that lets you talk to the Docker daemon.
  * **containerd.io** - A container runtime that manages the container’s lifecycle.
  * **docker-buildx-plugin** - This extension for Docker enhances the capabilities of building images, mainly focusing on multi-platform builds.
  * **docker-compose-plugin** - A configuration management plugin that helps manage multi-container Docker applications using a single YAML file.

</WRAP>

----

===== Verify that the installation is successful =====

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

returns:

<code>
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
e6590344b1a5: Pull complete 
Digest: sha256:0b6a027b5cf322f09f6706c754e086a232ec1ddba835c8a15c6cb74ef0d43c29
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/
</code>

<WRAP info>
**NOTE:**  This downloads a test image and runs it in a container.

  * When the container runs, it prints a confirmation message and exits.

  * If the command fails to run, try to restart the docker service, before rerunning this test: <code bash>
sudo systemctl restart docker.service
</code>

</WRAP>

----

===== To Uninstall Docker Engine =====

<code bash>
sudo apt purge docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin docker-ce-rootless-extras
</code>

Then, manually remove the following two directories:

<code bash>
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd
</code>

----

===== References =====

https://docs.docker.com/engine/install/ubuntu/

https://docs.docker.com/engine/install/ubuntu/#uninstall-docker-engine

https://docs.docker.com/engine/network/packet-filtering-firewalls/