方法1

需要首次使用public key链接SSH

echo root:YourPasswordHere |sudo chpasswd root
sudo sed -i 's/^#\?PermitRootLogin.*/PermitRootLogin yes/g' /etc/ssh/sshd_config;
sudo sed -i 's/^#\?PasswordAuthentication.*/PasswordAuthentication yes/g' /etc/ssh/sshd_config;
sudo service sshd restart

YourPasswordHere 为自定义密码

第二次就可以用root + 密码登录