A guide to installing Docker on Ubuntu 22.04

Docker on Ubuntu

Docker is a tool designed to streamline the process of creating, deploying, and running applications by using containers. Containers allow developers to package up an application with all the parts it needs, such as libraries and other dependencies, and ship it all out as one package. In this guide, we will walk you through the process of installing and using Docker Community Edition (CE) on Ubuntu 22.04.

Prerequisites for installing Docker on Ubuntu

Before you begin, you will need the following:

An Ubuntu 22.04 server set up by following the Ubuntu 22.04 initial server setup guide, including a sudo non-root user and a firewall.
An account on Docker Hub if you want to create your own images and push them to Docker Hub.

Steps for installing Docker on Ubuntu 22.04

Step 1: Set up the repository

The Docker installation package available in the official Ubuntu repository may not be the latest version. To get the latest version, we will install Docker from the official Docker repository. This involves adding a new package source, adding the GPG key from Docker to ensure the downloads are valid, and then installing the package.

First, update your existing list of packages by running the command:

Update the apt package index and install packages to allow apt to use a repository over HTTPS:

$ sudo apt-get update

$ sudo apt-get install ca-certificates curl gnupg

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

Use the following command to set up 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

Note: If you use an Ubuntu derivative distro, such as Linux Mint, you may need to use UBUNTU_CODENAME instead of VERSION_CODENAME.

Step 2: Install the Docker engine

Update the apt package index:

$ sudo apt-get update

Install Docker Engine, containerd, and Docker Compose.

To install the latest version, run:

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

Verify that the Docker Engine installation is successful by running the hello-world image.

$ sudo docker run hello-world

This command downloads a test image and runs it in a container. When the container runs, it prints a confirmation message and exits. You have now successfully installed and started Docker Engine.

Tip: Receiving errors when trying to run without root?

The docker user group exists but contains no users, which is why you’re required to use sudo to run Docker commands. Continue to Linux postinstall to allow non-privileged users to run Docker commands and for other optional configuration steps.

Step 3: Upgrade Docker engine

If you want to upgrade Docker engine, follow the installation instructions, choosing the new version you want to install.

Install from a package: If you can’t use Docker’s apt repository to install Docker Engine, you can download the deb file for your release and install it manually. You need to download a new file each time you want to upgrade Docker Engine.

Go to https://download.docker.com/linux/ubuntu/dists/. Select your Ubuntu version in the list.
Go to pool/stable/ and select the applicable architecture (amd64, armhf, arm64, or s390x).

Download the following deb files for the Docker Engine, CLI, containerd, and Docker Compose packages:

containerd.io_<version>_<arch>.deb
docker-ce_<version>_<arch>.deb
docker-ce-cli_<version>_<arch>.deb
docker-buildx-plugin_<version>_<arch>.deb
docker-compose-plugin_<version>_<arch>.deb

Install the .deb packages. Update the paths in the following example to where you downloaded the Docker packages.

$ sudo dpkg -i ./containerd.io_<version>_<arch>.deb \

./docker-ce_<version>_<arch>.deb \

./docker-ce-cli_<version>_<arch>.deb \

./docker-buildx-plugin_<version>_<arch>.deb \

./docker-compose-plugin_<version>_<arch>.deb

The Docker daemon starts automatically.

Verify that the Docker Engine installation is successful by running the hello-world image.

$ sudo service docker start

$ sudo docker run hello-world

This command downloads a test image and runs it in a container. When the container runs, it prints a confirmation message and exits.

You have now successfully installed and started Docker Engine.

Tip: Receiving errors when trying to run without root?

Step 4: Upgrade Docker engine

To upgrade Docker Engine, download the newer package files and repeat the installation procedure, pointing to the new files.

Install using the convenience script: Docker provides a convenience script at https://get.docker.com/ to install Docker into development environments non-interactively. The convenience script isn’t recommended for production environments, but it’s useful for creating a provisioning script tailored to your needs. Also refer to the install using the repository steps to learn about installation steps to install using the package repository. The source code for the script is open source, and you can find it in the docker-install repository on GitHub.

Always examine scripts downloaded from the internet before running them locally. Before installing, make yourself familiar with potential risks and limitations of the convenience script:

The script requires root or sudo privileges to run.
The script attempts to detect your Linux distribution and version and configure your package management system for you.
The script doesn’t allow you to customize most installation parameters.
The script installs dependencies and recommendations without asking for confirmation. This may install a large number of packages, depending on the current configuration of your host machine.
By default, the script installs the latest stable release of Docker, containerd, and runc. When using this script to provision a machine, this may result in unexpected major version upgrades of Docker. Always test upgrades in a test environment before deploying to your production systems.
The script isn’t designed to upgrade an existing Docker installation. When using the script to update an existing installation, dependencies may not be updated to the expected version, resulting in outdated versions.

Tip: preview script steps before running.

You can run the script with the –dry-run option to learn what steps the script will run when invoked:

$ curl -fsSL https://get.docker.com -o get-docker.sh

$ sudo sh ./get-docker.sh –dry-run

This example downloads the script from https://get.docker.com/ and runs it to install the latest stable release of Docker on Linux:

$ curl -fsSL https://get.docker.com -o get-docker.sh

$ sudo sh get-docker.sh

Executing docker install script, commit: 7cae5f8b0decc17d6571f9f52eb840fbc13b2737

<…>

You have now successfully installed and started Docker Engine. The docker service starts automatically on Debian based distributions. On RPM based distributions, such as CentOS, Fedora, RHEL or SLES, you need to start it manually using the appropriate systemctl or service command. As the message indicates, non-root users can’t run Docker commands by default.

Use Docker as a non-privileged user, or install in rootless mode?

The installation script requires root or sudo privileges to install and use Docker. If you want to grant non-root users access to Docker, refer to the post-installation steps for Linux. You can also install Docker without root privileges, or configured to run in rootless mode. For instructions on running Docker in rootless mode, refer to run the Docker daemon as a non-root user (rootless mode).

Step 5: Install pre-releases

Docker also provides a convenience script at https://test.docker.com/ to install pre-releases of Docker on Linux. This script is equal to the script at get.docker.com, but configures your package manager to use the test channel of the Docker package repository. The test channel includes both stable and pre-releases (beta versions, release-candidates) of Docker. Use this script to get early access to new releases, and to evaluate them in a testing environment before they’re released as stable.

To install the latest version of Docker on Linux from the test channel, run:

$ curl -fsSL https://test.docker.com -o test-docker.sh

$ sudo sh test-docker.sh

Step 6: Upgrade Docker after using the convenience script

If you installed Docker using the convenience script, you should upgrade Docker using your package manager directly. There’s no advantage to re-running the convenience script. Re-running it can cause issues if it attempts to re-install repositories which already exist on the host machine.

Conclusion of installing Docker on Ubuntu 22.04

In this guide, you learned how to install Docker, work with images and containers, and push a modified image to Docker Hub. Now you can explore other Docker tutorials to further enhance your knowledge.

Source: Docker

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