我apache_在 munin 节点上启用了插件：
ln -sv /usr/share/munin/plugins/apache_* /etc/munin/plugins/
用service munin-node restart这里重新启动节点后，我得到了错误：
$ munin-node-configure --suggest 2>/dev/null | grep "apache\|Plugin\|------"
Plugin | Used | Suggestions
------ | ---- | -----------
apache_accesses | yes | no [apache server-status not found. check if mod_status is enabled]
apache_processes | yes | no [apache server-status not found. check if mod_status is enabled]
apache_volume | yes | no [apache server-status not found. check if mod_status is enabled]
但是mod_status已经启用：
$ a2enmod status
Module …