Couldn't connect to Docker daemon at http+docker://localhost - is it running

使用docker-composer出现的一个问题:

[[email protected] wordpress]$ docker-compose up
ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

解决方法
方法1: 切换到root用户执行
方法2：把当前用户加入到docker组，这里以centos7为例

sudo groupadd docker
sudo gpasswd -a vagrant docker // 把当前用户vagrant加入到docke分组中
sudo service docker restart // 重启docker服务