每当我尝试在UNIX/Linux下启动Apache 2服务器并收到以下警告时：

[warn] NameVirtualHost *:80 has no VirtualHosts

我该如何解决这个问题？

NameVirtualHost指令是配置基于名称的虚拟主机所必需的。
您需要编辑Apache配置文件httpd.conf或apache2.conf，输入：

# vi httpd.conf

查找如下所示的行：

<VirtualHost *>

替换如下：

NameVirtualHost *:80
<VirtualHost *:80>

保存并关闭文件。
这是示例配置文件：

# My Virtual Hosts Config File for two Domains
NameVirtualHost *:80
 
<VirtualHost *:80>
    ServerAdmin [email protected]
    DocumentRoot "/usr/local/docs/theos.in"
    ServerName www.theos.in
    ServerAlias theos.in
    ErrorLog "/var/log/theos.in-error_log"
    CustomLog "/var/log/theos.in-access_log" common
</VirtualHost>
 
<VirtualHost *:80>
    ServerAdmin [email protected]
    DocumentRoot "/usr/local/docs/theitroad.com"
    ServerName www.theitroad.com
    ServerAlias theitroad.com
    ErrorLog "/var/log/theitroad.com-error_log"
    CustomLog "/var/log/theitroad.com-access_log" common
</VirtualHost>

保存并关闭文件。
最后，重新启动Apache：

# /etc/init.d/apache2 restart

要么

# service httpd restart