以前遇到一个问题：
sudo /etc/init.d/apache2 start
* Starting web server apache2
apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName
()Address already in use: make_sock: could not bind to address 0.0.0.0:
no listening sockets available, shutting down
Unable to open logs
其实就是80端口被占用的原因，解决办法如下：
sudo fuser -k -n tcp sudo /etc/init.d/apache2 start