apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName错误的解决方法

apache在启动时出现apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName错误，其解决方法如下：
在/etc/apache2/conf.d/目录下创建一个新文件fqdn，并写入内容“ServerName localhost”：
echo "ServerName localhost" | sudo tee /etc/apache2/conf.d/fqdn
sudo /etc/init.d/apache2 restart
重启apache2解决问题。