Update README

README.md

@@ -17,9 +17,32 @@ To determine the number of mails for these graphs the recent (5 minutes, hardcod
 syslog entries are grep'ed for signaling sequences indicating some kind of
 action of postfix.
 
+Install
+-------
+
+Clone this repository or download the postfix_mailqueue file and create a
+symlinkas *root* in /etc/munin/plugins by using e.g.:
+
+	cd /etc/munin/plugins; ln -s /your/path/to/postfix_mailqueue postfix_mailqueue
+
+Since this script does not honor a environment variable to locate your
+*mail.log* you currently have to set the `MAILLOG` variable (which defaults
+to */var/log/mail.log*) in the script's header.
+
+Next make sure that munin is allowed or at least allows this script to read
+your *mail.log*. How to do this depends on your system.
+
+On Debian 6 *mail.log* is owned by `root:adm` and readable by nobody but them.
+The recommended way here is to advice munin to run postfix_mailqueue with group
+adm (and user postfix, by default) by modifying */etc/munin/plugin-conf.d/munin-node*
+where you should change/add a line to the `[postfix_mailqueue]` section:
+
+	group adm
+
+Later you will set the *mail.log* path here, too.
+
 syslog5mins
 -----------
 
 This little script returns the entries of a (syslog created) file of the last
 5 minutes.
-**You should modify the scripts location in postfix_mailqueue script!**