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To get started with Docker Engine on CentOS, make sure youmeet the prerequisites, theninstall Docker.

Install Docker CE on CentOS 8 RHEL 8. So far we have covered docker introduction and terminologies. We should be ready to install Docker CE on RHEL 8 / CentOS 8. We will start with the installation of Docker then Docker Compose. There are two editions of Docker available. The list returned depends on which repositories are enabled, and is specific to your version of CentOS (indicated by the.el7 suffix in this example). Install a specific version by its fully qualified package name, which is the package name (docker-ce) plus the version string (2nd column) starting at the first colon (:), up to the first hyphen, separated by a hyphen (-). Install Docker on CentOS # Although the Docker package is available in the official CentOS 7 repository, it may not always be the latest version. The recommended approach is to install Docker from the Docker’s repositories. To install Docker on your CentOS 7 server follow the steps below: Start by updating your system packages and install the. INSTALLATION OF DOCKER FAILS ON CENTOS 8 WITH ERROR – PACKAGE CONTAINERD.IO-1.2.10-3.2.EL7.X8664 IS EXCLUDED; SOME BASIC DOCKER COMMANDS BEGINNER SHOULD KNOW; In this tutorial helps you to install Docker on CentOS/RHEL 8. Step 1: Uninstall Old Versions.

Prerequisites

OS requirements

To install Docker Engine, you need a maintained version of CentOS 7 or 8.Archived versions aren’t supported or tested.

The centos-extras repository must be enabled. This repository is enabled bydefault, but if you have disabled it, you need tore-enable it.

The overlay2 storage driver is recommended.

Uninstall old versions

Older versions of Docker were called docker or docker-engine. If these areinstalled, uninstall them, along with associated dependencies.

It’s OK if yum reports that none of these packages are installed.

The contents of /var/lib/docker/, including images, containers, volumes, andnetworks, are preserved. The Docker Engine package is now called docker-ce.

Installation methods

You can install Docker Engine in different ways, depending on your needs:

  • Most usersset up Docker’s repositories and installfrom them, for ease of installation and upgrade tasks. This is therecommended approach.

  • Some users download the RPM package andinstall it manually and manageupgrades completely manually. This is useful in situations such as installingDocker on air-gapped systems with no access to the internet.

  • In testing and development environments, some users choose to use automatedconvenience scripts to install Docker.

Install using the repository

Before you install Docker Engine for the first time on a new host machine, you needto set up the Docker repository. Afterward, you can install and update Dockerfrom the repository.

Set up the repository

Install the yum-utils package (which provides the yum-config-managerutility) and set up the stable repository.

Optional: Enable the nightly or test repositories.

These repositories are included in the docker.repo file above but are disabledby default. You can enable them alongside the stable repository. The followingcommand enables the nightly repository.

To enable the test channel, run the following command:

You can disable the nightly or test repository by running theyum-config-manager command with the --disable flag. To re-enable it, usethe --enable flag. The following command disables the nightly repository.

Learn about nightly and test channels.

Install Docker Engine

Start Docker Centos 8

  1. Install the latest version of Docker Engine and containerd, or go to the next step to install a specific version:

    If prompted to accept the GPG key, verify that the fingerprint matches060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35, and if so, accept it.

    Got multiple Docker repositories?

    If you have multiple Docker repositories enabled, installingor updating without specifying a version in the yum install oryum update command always installs the highest possible version,which may not be appropriate for your stability needs.

    Docker is installed but not started. The docker group is created, but no users are added to the group.

  2. To install a specific version of Docker Engine, list the available versionsin the repo, then select and install:

    a. List and sort the versions available in your repo. This example sorts results by version number, highest to lowest, and is truncated:

    The list returned depends on which repositories are enabled, and is specificto your version of CentOS (indicated by the .el7 suffix in this example).

    b. Install a specific version by its fully qualified package name, which is the package name (docker-ce) plus the version string (2nd column) starting at the first colon (:), up to the first hyphen, separated by a hyphen (-). For example, docker-ce-18.09.1.

    Docker is installed but not started. The docker group is created, but no users are added to the group.

  3. Start Docker.

  4. Verify that Docker Engine is installed correctly by running the hello-worldimage.

    This command downloads a test image and runs it in a container. When thecontainer runs, it prints an informational message and exits.

Docker Engine is installed and running. You need to use sudo to run Dockercommands. Continue to Linux postinstall to allownon-privileged users to run Docker commands and for other optional configurationsteps.

Docker Start Centos Linux

Upgrade Docker Engine

To upgrade Docker Engine, follow the installation instructions,choosing the new version you want to install.

Install from a package

If you cannot use Docker’s repository to install Docker, you can download the.rpm file for your release and install it manually. You need to downloada new file each time you want to upgrade Docker Engine.

  1. Go to https://download.docker.com/linux/centos/and choose your version of CentOS. Then browse to x86_64/stable/Packages/and download the .rpm file for the Docker version you want to install.

    Note: To install a nightly or test (pre-release) package,change the word stable in the above URL to nightly or test.Learn about nightly and test channels.

  2. Install Docker Engine, changing the path below to the path where you downloadedthe Docker package.

    Docker is installed but not started. The docker group is created, but nousers are added to the group.

  3. Start Docker.

  4. Verify that Docker Engine is installed correctly by running the hello-worldimage.

    This command downloads a test image and runs it in a container. When thecontainer runs, it prints an informational message and exits.

Docker Engine is installed and running. You need to use sudo to run Docker commands.Continue to Post-installation steps for Linux to allownon-privileged users to run Docker commands and for other optional configurationsteps.

Upgrade Docker Engine

To upgrade Docker Engine, download the newer package file and repeat theinstallation procedure, using yum -y upgradeinstead of yum -y install, and pointing to the new file.

Install using the convenience script

Docker provides convenience scripts at get.docker.comand test.docker.com for installing edge andtesting versions of Docker Engine - Community into development environments quickly andnon-interactively. The source code for the scripts is in thedocker-install repository.Using these scripts is not recommended for productionenvironments, and you should understand the potential risks before you usethem:

  • The scripts require root or sudo privileges to run. Therefore,you should carefully examine and audit the scripts before running them.
  • The scripts attempt to detect your Linux distribution and version andconfigure your package management system for you. In addition, the scripts donot allow you to customize any installation parameters. This may lead to anunsupported configuration, either from Docker’s point of view or from your ownorganization’s guidelines and standards.
  • The scripts install all dependencies and recommendations of the packagemanager without asking for confirmation. This may install a large number ofpackages, depending on the current configuration of your host machine.
  • The script does not provide options to specify which version of Docker to install,and installs the latest version that is released in the “edge” channel.
  • Do not use the convenience script if Docker has already been installed on thehost machine using another mechanism.

This example uses the script at get.docker.com toinstall the latest release of Docker Engine - Community on Linux. To install the latesttesting version, use test.docker.com instead. Ineach of the commands below, replace each occurrence of get with test.

Warning:

Always examine scripts downloaded from the internet beforerunning them locally.

If you would like to use Docker as a non-root user, you should now consideradding your user to the “docker” group with something like:

Remember to log out and back in for this to take effect!

Warning:

Adding a user to the “docker” group grants them the ability to run containerswhich can be used to obtain root privileges on the Docker host. Refer toDocker Daemon Attack Surfacefor more information.

Docker Engine - Community is installed. It starts automatically on DEB-based distributions. OnRPM-based distributions, you need to start it manually using the appropriatesystemctl or service command. As the message indicates, non-root users can’trun Docker commands by default.

Note:

To install Docker without root privileges, seeRun the Docker daemon as a non-root user (Rootless mode).

Upgrade Docker after using the convenience script

If you installed Docker using the convenience script, you should upgrade Dockerusing your package manager directly. There is no advantage to re-running theconvenience script, and it can cause issues if it attempts to re-addrepositories which have already been added to the host machine.

Uninstall Docker Engine

  1. Uninstall the Docker Engine, CLI, and Containerd packages:

  2. Images, containers, volumes, or customized configuration files on your hostare not automatically removed. To delete all images, containers, andvolumes: Install windows 10 using bootcamp.

You must delete any edited configuration files manually.

Next steps

  • Continue to Post-installation steps for Linux.
  • Review the topics in Develop with Docker to learn how to build new applications using Docker.
requirements, apt, installation, centos, rpm, install, uninstall, upgrade, update

Installing Docker on Ubuntu is simple because Ubuntu provides Docker in its repositories. However, Docker is not available in CentOS's default repositories.

Fret not, there are three ways you can install docker on a CentOS Linux system.

  • Using docker's repository
  • Downloading the RPM
  • Using helper scripts

Here, I'll walk you through the installation process of Docker CE using docker's RPM repository.

Docker CE stands for Docker Community Edition. This is the free and open source version of Docker. There is Docker EE (Enterprise Edition) with paid support. Most of the world uses Docker CE and it is often considered synonymous to Docker.

Installing Docker on CentOS

Before going any further, make sure you have the system updated. You can update the CentOS using:

Step 1: Add the official repository

Add docker's official repository using the following command

You should also update the package cache after adding a new repository:

Step 2: Install Docker CE

The trouble with using a custom repository is that it may have dependency issue if you try installing the latest version of docker-ce.

For example, when I check the available versions of docker-ce with this command:

I got docker-ce-3:19.03.9-3.el7 as the latest version. But the problem in installing the latest version is that it depends on containerd.io version >=1.2.2-3. Now, this version of containerd.io is not available in CentOS 8.

To avoid this dependency cycle and battling them manually, you can use the --nobest option of the dnf command.

It will check the latest version of docker-ce but when it finds the dependency issue, it checks the next available version of docker-ce. Basically, it helps you automatically install the most suitable package version with all the dependencies satisfied.

To install docker in CentOS without getting a migraine, try this command and see the magic unfold on your terminal screen:

You'll be prompted to import a GPG key, make sure the key matches to 060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35 before entering 'y'.

containerd.io is a daemon for managing containers. Docker is just one form of Linux containers. To make the various types of container images portable, Open Container Initiative has defined some standards. containerd is used for managing the container images conforming to OCI standard.

Setting up docker on CentOS

Alright! You have docker installed but it's not yet ready to be used yet. You'll have to do some basic configurations before it can be used smoothly.

Run docker without sudo

You can run docker without any sudo privileges by adding your user to the docker group.

Docker Start Centos

The docker group should already exist. Check that using the following command:

If this outputs nothing, create the docker group using groupadd command like this:

Now add your user to the docker group using the usermod command:

Change the user_name in the above command with the intended user name.

Now log out and log back in for the group change to take effect.

Start docker daemon

Docker is installed. Your user has been added to the docker group. But that's not enough to run docker yet.

Before you can run any container, the docker daemon needs to be running. The docker daemon is the program that manages all the containers, volumes, networks etc. In other words, the daemon does all the heavy lifting.

Start the docker daemon using:

You can also enable docker daemon to start automatically at boot time:

Verify docker installation by running a sample container

Everything is done. It's time to test whether the installation was successful or not by running a docker container.

To verify, you can run the cliché hello-world docker container. It is a tiny docker image and perfect for quickly testing a docker installation.

If everything is fine, you should see an output like this:

Here's what the command is doing behind the hood:

  • The docker client, i.e. the command line tool that you just used, contacted the docker daemon.
  • The daemon looked for hello-world docker image in the local system. Since it doesn't find the image, it pulls it from Docker Hub.
  • The engine creates the container with all the options you provided through the client's command line options.

This hello-world image is used just for testing a docker installation. If you want a more useful container, you can try running Nginx server in a container like this:

Once the command is done running, open up a browser and go to http://your_ip_address:56788. I hope you know how to know your IP address in Linux.

You should see nginx server running. You can stop the container now.

I hope this tutorial helped you in installing docker on CentOS. Do subscribe for more Docker tutorials and DevOps tips.

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