1）去除GSS认证
    2）去除DNS
    3）重启

    sudo sed -i “s/^.GSSAPIAuthentication./GSSAPIAuthentication no/g” /etc/ssh/sshd_config
    sudo sed -i “s/^.UseDNS./UseDNS no/g” /etc/ssh/sshd_config
    sudo systemctl restart sshd

    4）允许root 登录
    5）允许密码登录
    sudo sed -i “s/^.PermitRootLogin./PermitRootLogin yes/g” /etc/ssh/sshd_config
    sudo sed -i “s/^.PasswordAuthentication./PasswordAuthentication yes/g” /etc/ssh/sshd_config