debian更新后，apache启动报错

# service apache2 restart
[....] Restarting web server: apache2apache2: Could not reliably determine the server's fully qualified domain name, using **.**.**.** for ServerName
... waiting apache2: Could not reliably determine the server's fully qualified domain name, using **.**.**.** for ServerName
. ok
请问诸位是呵原因，如何解决？谢谢！