Centos7 安装 Docker

1. 卸载旧版本，如果已安装较旧版本的Docker，请卸载它们以及相关的依赖项。

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

2. 安装所需的包

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

3. 添加 yum 软件源，推荐国内镜像，如果不能使用在修改为官方镜像。

$ sudo yum-config-manager \
    --add-repo \
    https://mirrors.ustc.edu.cn/docker-ce/linux/centos/docker-ce.repo

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

4. 安装 Docker CE

$ sudo yum makecache fast
$ sudo yum -y install docker-ce

5. 启动 Docker CE

$ sudo systemctl enable docker
$ sudo systemctl start docker

6. 测试 Docker 是否安装正确

$ sudo docker run hello-world

能正常输出以下信息，说明安装成功

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete 
Digest: sha256:b8ba256769a0ac28dd126d584e0a2011cd2877f3f76e093a7ae560f2a5301c00
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/

参考文档：
https://yeasy.gitbooks.io/docker_practice/content/install/centos.html
https://docs.docker.com/install/linux/docker-ce/centos/