应该是sshd的设置不允许root用户用密码远程登录
1、修改 vim /etc/ssh/sshd_config
找到# Authentication:
LoginGraceTime 120
PermitRootLogin without passwd
StrictModes yes
改成
# Authentication:
LoginGraceTime 120
PermitRootLogin yes
StrictModes yes
2、重启ssh
systemctl restart sshd