ambari安装hadoop Host checks were skipped on 3 hosts that failed to register.

ambari 2.7.1安装hadoop时报错。
Host checks were skipped on 3 hosts that failed to register.

一开始网上找，试过几个都没解决，后来发现是主机名没配好。
以前centos6 是 vim /etc/sysconfig/network 里面改
现在用centos7，上面的改完还不生效，改：vim /etc/hostname
centos7重启这个服务：systemctl restart systemd-hostnamed
hostname 查看还是没生效。
重启，查看，修改成功。
然后在ambari上点击进入下一步。。