本文总结如何在CentOS中安装Docker Engine
〇、Docker Engine 介绍
Docker Engine是一种开源容器化技术，用于构建和容器化应用程序。Docker引擎作为一个客户端-服务器应用程序:
- 具有长时间运行守护进程的服务器。
- 指定接口的api，程序可以使用这些接口与Docker守护进程通信并向其发出指令。
- 命令行接口(CLI)客户端docker。
CLI使用Docker api通过脚本或直接的CLI命令来控制Docker守护进程或与之交互。许多其他Docker应用程序使用底层API和CLI。守护进程创建和管理Docker对象，如镜像、容器、网络和卷。
一、先决条件
1. 系统要求
要求CentOS版本为： CentOS 7/CentOS 8/CentOS 8 Stream/CentOS 9 Stream
要求centos-extras仓库配置开启（默认是开启的）
如果你的yum源有问题请参考：
CentOS 执行yum命令报错【错误：为仓库 ‘appstream‘ 下载元数据失败: …】
如下是CentOS8中的CentOS-Linux-Extras.repo，要求enabled=1
[root@GC yum.repos.d]# cat /etc/yum.repos.d/CentOS-Linux-Extras.repo
# CentOS-Linux-Extras.repo
# ...
[extras]
name=CentOS Linux $releasever - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
baseurl=https://mirrors.aliyun.com/centos-vault/8.4.2105/extras/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
2. 卸载旧版本
卸载旧版本的docker or docker-engine，如果你使用的是新安装的CentOS，可以忽略该步骤
执行如下命令，进行卸载
sudo yum remove docker \
docker-client \
docker-client-latest \
docker-common \
docker-latest \
docker-latest-logrotate \
docker-logrotate \
docker-engine
示例（root用户无需加sudo）：
[root@GC ~]# yum remove docker \
> docker-client \
> docker-client-latest \
> docker-common \
> docker-latest \
> docker-latest-logrotate \
> docker-logrotate \
> docker-engine
Failed to set locale, defaulting to C.UTF-8
No match for argument: docker
No match for argument: docker-client
No match for argument: docker-client-latest
No match for argument: docker-common
No match for argument: docker-latest
No match for argument: docker-latest-logrotate
No match for argument: docker-logrotate
No match for argument: docker-engine
No packages marked for removal.
Dependencies resolved.
Nothing to do.
Complete!
[root@GC ~]
因为我是新安装的，所以：No packages marked for removal
二、安装 Docker Engine
安装Docker Engine的方式有多种，本文使用Docker仓库安装
1. 设置Docker仓库
sudo yum install -y yum-utils
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
安装yum-utils包，然后使用该包下的yum-config-manager命令配置Docker仓库
2. 安装Docker引擎
安装最新版本的Docker Engine、containerd、 Docker Compose等
sudo yum install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
3. 启动docker
sudo systemctl start docker
如果你使用systemctl命令报错，请参考：
使用systemctl命令报错:System has not been booted with systemd as init system (PID 1). Can‘t operate.
4. 验证docker安装是否成功
sudo docker run hello-world
如下，可正常运行hello-world表示安装成功了。
[root@GC ~]# docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
719385e32844: Pull complete
Digest: sha256:dcba6daec718f547568c562956fa47e1b03673dd010fe6ee58ca806767031d1c
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/
[root@GC ~]#
三、卸载Docker
如果你需要卸载Docker，可以参考如下命令：
sudo yum remove docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin docker-ce-rootless-extras
上述命令，不会删除images、containers、volumes等数据，
你可以再执行如下命令进行删除：
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd