啟動Apache時出現[AH00558: apache2: Could not reliably determine the server's fully qualified domain name]

目前使用的方法有二種：
一、apache2.conf
sudo vim apache2.conf
在最後加上ServerName localhost

二、新增servername.conf
sudo vim /etc/apache2/conf-enabled/servername.conf
只加一行
ServerName localhost