Install Docker in CentOS 8.4

created at 11-17-2021 views: 30

preface

Docker is an open platform for developing, delivering and running applications. Docker enables you to separate applications from infrastructure so that you can deliver software quickly. With Docker, you can manage the infrastructure like an application. By taking advantage of Docker's rapid code delivery, testing, and deployment methods, you can significantly reduce the delay between writing code and running it in production. In order to make development, deployment, testing and distribution more efficient and easy, let's install Docker and experience its charm!

System Requirements

  • Docker supports the 64-bit version of CentOS 7/8, and requires the kernel version to be at least 3.10.
  • Need to enable centos-extras repository. In CentOS 7 this repository is enabled by default, if you 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 overlay2 storage layer driver) cannot be used, and some functions may not be stable.

Installation Environment

This article is mainly to install Docker in the Liunx operating system CentOS8.4, we can check our system version before installing, use the command: lsb_release -a to view (as shown in the figure below).

Note: Do not directly use the yum command to install Docker without configuring the Docker YUM source.

Installation Environment

Uninstall old version

The package name of the old version of Docker in CentOS is docker or docker-engine. If you installed an old version of Docker in your previous Linux CentOS system, you need to uninstall the old version of Docker and its related dependencies first, and execute 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 has just been installed, the execution of the above command prompts that the package that needs to be removed is not found!

uninstall docker

If yum reports that these packages are not installed, it does not matter.

Note: The contents of the /var/lib/docker/ directory, including files such as images, containers, volume groups, and networks, will be preserved. The new package of Docker CE is named docker-ce.

What exactly does yum do?

Brief description: Yum is called a package manager, which is mainly used to solve four problems: download, dependency, installation, and uninstall.

Install with yum:

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

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

Configure yum stable mirror source:

Due to network in China, it is recommended to use the Docker CE mirror source site provided by Alibaba Cloud!

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

mirror

Official mirror source address:

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

Install Docker

Update the yum software source cache and install docker-ce (yes all the way).

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

The following are the dependencies for successful installation:

installed successfully

View the successfully installed docker version: 

docker -v

docker version

CentOS8 extra settings

Since the CentOS8 firewall uses nftables, Docker does not yet support nftables.

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

systemctl status firewalld

firewall closed

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:

Executing the sudo service docker start command to start the Docker service prompts an exception: Redirecting to /bin/systemctl start docker.service

start docker successfully

To see the exception, you need to execute systemctl related commands, because different Linux distributions have different commands to open the Docker service.

sudo systemctl enable docker
sudo systemctl start docker

Finally check the running status of docker

systemctl status docker

Start the Docker daemon

Manual start

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

sudo systemctl start docker

Automatically start when the system starts

If you want Docker to start at boot time, please refer to 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
  • View docker status: systemctl status docker
  • Boot start: 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 image: docker image ls

Test if Docker is installed correctly

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

Note: This command will let Docker pull the image of hello-world from the official warehouse to the local (when the image does not exist locally), and it will automatically instantiate the container.

test docker

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 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/

View the hello-World image and container:

image id

container

ref:

created at:11-17-2021
edited at: 11-17-2021: