通常我們使用Docker的時候都是使用的root，官方說法如下：

The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can access it with sudo. For this reason, docker daemon always runs as the root user.
To avoid having to use sudo when you use the docker command, create a Unix group called docker and add users to it. When the docker daemon starts, it makes the ownership of the Unix socket read/writable by the docker group.
下面是使用非root用戶操作的步驟

創建docker組

sudo groupadd docker

將當前用戶加入docker組

sudo gpasswd -a ${USER} docker

重新啟動docker服務（下面是CentOS7的命令）

sudo systemctl restart docker

當前用戶退出系統重新登陸

運行docker命令

docker ps

Docker使用非root用戶