在CentOS7.6、红帽7.6系统中安装Docker：

yum install -y docker
systemctl start docker.service
systemctl enable docker.service

注意：需要root权限。

命令详情具体如下。

一、卸载旧版本

卸载旧版本（如果安装过的话）

sudo yum remove docker \
docker-common \
docker-selinux \
docker-engine

二、安装Docker

docker软件包已经包括在CentOS7默认的CentOS-Extras软件源。因此想要安装 docker，只需要运行下面的 yum 命令：

# 安装docker
yum install -y docker

# 启动docker,并设置开机启动
systemctl start docker.service
systemctl enable docker.service

三、测试是否安装成功

通过运行简单的Docker镜像hello-world来测试安装是否有效 ：

 docker run hello-world

执行该命令打印的信息中包含如下提示信息时，说明安装成功：

Hello from Docker!
This message shows that your installation appears to be working correctly.

完整打印信息：

[root@chushiyan ~]# docker run hello-world
Unable to find image 'hello-world:latest' locally
Trying to pull repository docker.io/library/hello-world ... 
latest: Pulling from docker.io/library/hello-world
1b930d010525: Pull complete 
Digest: sha256:2557e3c07ed1e38f26e389462d03ed943586f744621577a99efb77324b0fe535
Status: Downloaded newer image for docker.io/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/