Document basic requirements of installation

Author: renatomefi

README.md

@@ -6,6 +6,29 @@ This POSIX compliant sh script gets php-fpm status page using `cgi-fcgi` tool, p
 
 ## Installation
 
+### Enable php-fpm status page
+
+On you php-fpm pool configuration add: `pm.status_path = /status`
+
+For instance on the official php image you can alter the file `/usr/local/etc/php-fpm.d/zz-docker.conf`
+
+[See a simple example](https://github.com/renatomefi/php-fpm-healthcheck/blob/master/test/Dockerfile#L7)
+
+[More about PHP fpm pool configuration](http://php.net/manual/en/install.fpm.configuration.php)
+
+### Requirements
+
+The script is POSIX sh but also uses some tools from your operating system, being:
+
+- cgi-fcgi
+- sed
+- tail
+- grep
+
+In case you're using alpine you only need to make sure you have installed `busybox` and `fcgi` packages.
+
+[See a simple Dockerfile based on the official PHP image](https://github.com/renatomefi/php-fpm-healthcheck/blob/master/test/Dockerfile)
+
 ### Download
 
 ```sh