运行docker镜像时出如下错误：
docker: Error response from daemon: OCI runtime create failed: systemd cgroup flag passed, but systemd support for managing cgroups is not available: unknown.
cat daemon.json
{
"registry-mirrors": ["https://registry.docker-cn.co"],
"exec-opts": ["native.cgroupdriver=systemd"]
}
因为指定了systemd，导致文件docker 运行镜像失败，
解决方法，去掉
"exec-opts": ["native.cgroupdriver=systemd"]
重启docker 服务
service docker restart
