kubeadm 初始化时候报的警告信息：

[preflight] Running pre-flight checks
    [WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/

解决

# 修改docker配置文件添加参数
# 设置默认cgroup组为systemd（centos7中有2个cgrounp组，cgroupfs和systemd）

/etc/docker/daemon.json
{
   "exec-opts": ["native.cgroupdriver=systemd"]
}

# 重启docker
systemctl daemon-reload
systemctl restart docker