Detailed tutorial on installing Docker on CentOS 8.4

Preface:

Docker is an open platform for developing, shipping, and running applications. Docker enables you to separate applications from infrastructure so that you can deliver software quickly. With Docker, you can manage your infrastructure just like you manage your applications. By leveraging Docker's method of rapidly delivering, testing, and deploying code, you can significantly reduce the delay between writing code and running it in production. To make development, deployment, testing, and distribution more efficient and easier, let's install Docker and experience its charm!

System Requirements:

• Docker supports 64-bit versions of CentOS 7/8 and requires the kernel version to be no less than 3.10.
• The centos-extrasrepository needs to be enabled. This repository is enabled by default in CentOS 7. If you have disabled it before, you need to re-enable it.
• CentOS 7 meets the minimum kernel requirements, but due to the relatively low kernel version, some functions (such as the overlay2 storage layer driver) cannot be used, and some functions may be unstable.

Installation environment:

This article mainly installs Docker in the Liunx operating system CentOS8.4. Before installation, we can check our system version by using the command: lsb_release -a (as shown in the figure below).

Note: Do not install Docker using the yum command without configuring the Docker YUM repository.

Uninstall old versions:

The package name of the old version of Docker in CentOS is docker or docker-engine. If you have installed an old version of Docker on your Linux CentOS system, you need to uninstall the old version of Docker and its related dependencies by executing the following command:

sudo yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-selinux \
                  docker-engine-selinux \
                  docker-engine

Because my system was just installed, when I executed the above command, it prompted that no package to be removed was found!

If yum reports that the packages are not installed, that's OK.

Note: The contents of the /var/lib/docker/ directory, including images, containers, volume groups, networks, and other files, will be retained. The new package name for Docker CE is docker-ce .

What exactly does yum do?

Simple description: yum is called a package manager, which is mainly used to solve four problems: downloading, dependency, installation, and uninstallation.

Detailed description: https://www.jb51.net/article/165658.htm

Install using yum:

Execute the following commands to install dependency packages and some necessary system tools:

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

Configure yum stable mirror source:

Due to domestic network reasons, it is recommended to use the Docker CE image source station provided by Alibaba Cloud!

sudo yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo 

Official mirror source address:

# Official source# sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Install Docker

Update yum software source cache and install docker-ce（一路yes即可） .

sudo yum install docker-ce docker-ce-cli containerd.io

The following are the dependencies that were successfully installed:

Check the successfully installed docker version: docker -v

CentOS8 Additional Settings

Since CentOS8 firewall uses nftables , but Docker does not yet support nftables。

First, we check the status of the firewall. If the firewall status is turned on, we perform the following operations:

systemctl status firewalld 

We can use iptables with the following settings: Change /etc/firewalld/firewalld.conf

# FirewallBackend=nftables
FirewallBackend=iptables

Or execute the following command:

firewall-cmd --permanent --zone=trusted --add-interface=docker0
 
firewall-cmd --reload

Start the Docker service:

Execute the sudo service docker start command to start the Docker service and an exception is displayed: Redirecting to /bin/systemctl start docker.service

If you see an exception, you need to execute the relevant systemctl commands, because different Linux distributions have different commands for starting the Docker service.

sudo systemctl enable docker
sudo systemctl start docker

Finally check the docker running status

systemctl status docker 

Start the Docker daemon:

Official tutorial: https://docs.docker.com/config/daemon/systemd/

Manual Start

After installing Docker, you need to start the Docker daemon. Most Linux distributions use systemctl to start services.

sudo systemctl start docker

Automatically start at system boot

If you want Docker to start at boot time, see Configure Docker to start at boot time 👉.

Docker basic commands:

Start Docker: systemctl start docker

Stop Docker: systemctl stop docker

Restart Docker: systemctl restart docker

Check the docker status: systemctl status docker

Start at boot: systemctl enable docker

Current system docker information: docker info

List all containers: docker ps -a

Stop the container: docker start container ID or container name

Close the container directly: docker kill container ID or container name

Restart the container: docker restart container ID or container name

Delete container: docker rm container ID or container name

View the image: docker image ls

More command searches (recommended): Docker command online quick reference manual

Test whether Docker is installed correctly

First, we enter docker run hello-world to see if the prompt shown in the figure below appears. If an error occurs, there may be a problem with the environment configuration.

Note: This command will cause Docker to pull the hello-world image from the official repository to the local computer (if the image does not exist locally), and automatically instantiate a container for it.

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
2db29710123e: Pull complete
Digest: sha256:37a0b92b08d4919615c3ee023f7ddb068d12b8387475d64c622ac30f45c29c51
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 creates 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/

View the hello-World image and container:

Docker learning series

day1, comprehensive Docker quick start tutorial 👉

Day 2, CentOS 8.4 install Docker👉

Reference articles:

Install Docker Engine on CentOS

CentOS 7 (install using yum)

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