前提
首先，你的Centos的系统一定要是64位的，不管版本是什么。并且内核版本至少是3.10以上。
用以下命令去查看你的内核版本：
$ uname -r
3.10.0-229.el7.x86_64
用yum安装
用具有sudo或者root权限的用户登录系统。
确保你的yum包已经更新。
$ sudo yum update
添加yum仓库
$ sudo tee /etc/yum.repos.d/docker.repo <<-'EOF'
添加如下内容：
[dockerrepo]
name=Docker Repository
baseurl=https://yum.dockerproject.org/repo/main/centos/$releasever/
enabled=1
gpgcheck=1
gpgkey=https://yum.dockerproject.org/gpg
EOF
结束回车即可
安装Docker包
$ sudo yum install docker-engine
镜像加速
鉴于国内网络问题，后续拉取 Docker 镜像十分缓慢，我们可以需要配置加速器来解决，我使用的是阿里的镜像地址：
在/etc/docker/daemon.json文件中添加如下内容.
{
"registry-mirrors": ["https://wghlmi3i.mirror.aliyuncs.com"]
}
或者使用如下地址
{
"registry-mirrors": ["https://registry.docker-cn.com"]
}
启动 Docker 后台服务
[root@docker-node1 ~]# systemctl start docker.service
到此，docker 在 CentOS 系统的安装完成。
验证是否成功：
[root@dtc ~]# docker version
Client:
Version: 18.09.5
API version: 1.39
Go version: go1.10.8
Git commit: e8ff056
Built: Thu Apr 11 04:43:34 2019
OS/Arch: linux/amd64
Experimental: false
Server: Docker Engine - Community
Engine:
Version: 18.09.5
API version: 1.39 (minimum version 1.12)
Go version: go1.10.8
Git commit: e8ff056
Built: Thu Apr 11 04:13:40 2019
OS/Arch: linux/amd64
Experimental: false
[root@dtc ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
[root@dtc ~]#
[root@dtc ~]# docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete
Digest: sha256:92695bc579f31df7a63da6922075d0666e565ceccad16b59c3374d2cf4e8e50e
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:
- The Docker client contacted the Docker daemon.
- The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64) - The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading. - 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@dtc ~]#
[root@dtc ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
hello-world latest fce289e99eb9 3 months ago 1.84kB
[root@dtc ~]#
此处hello-world已经出现，成功。
安装遇到的问题：
centos7安装docker出现Cannot connect to the Docker daemon at tcp://0.0.0.0:2375. Is the docker dae...
管理端口在 /lib/systemd/system/docker.service 文件中
将其中的 ExecStart=/usr/bin/dockerd 替换为：
ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock -H tcp://0.0.0.0:7654
（此处默认2375为主管理端口，unix:///var/run/docker.sock用于本地管理，7654是备用的端口）
将管理地址写入 /etc/profile
echo 'export DOCKER_HOST=tcp://0.0.0.0:2375' >> /etc/profile
使profile生效
如果出现：Warning: docker.service changed on disk. Run 'systemctl daemon-reload' to reload units.
根据提示执行：systemctl daemon-reload
然后重启：systemctl restart docker.service