Once you have started to manage tens of servers with CFEngine (great!), if you stick to mail reports you will quickly become overwhelmed. To classify them more easily, here is a trick with CFEngine-3.6.
By default the subject is [fqdn/ip], for example (mail headers)
Not very easy to filter them through your email client (in case you don’t/can’t use a powerful MDA like procmail) without clashing with others similar subjects.
Here comes the mailsubject option of cf-execd, which allows you to set your own mail subject through body executor control. The cf-execd configuration lies in the /var/cfengine/inputs/controls/cf_execd.cf file.
Example from the documentation:
body executor control
mailsubject => "CFEngine report ($(sys.fqhost))";
Which gives (mail headers):
Subject: CFEngine report (debian70.boring)
Easier to filter, easy to customize with all the CFEngine variables available, and a little undocumented bonus, an extra X-CFEngine: mail header is added when this option is set:
X-CFEngine: vfqhost="debian71.boring";ip-addresses="127.0.0.1 192.168.1.111 fe80::a00:24fe:9eab:77ba";policyhub="192.168.1.110";..."
But this time, no way to customize it.
There is a pull request to add this header even if mailsubject option is not set, if you are interested in, please add a comment to the GitHub entry!
Latest extra, the corresponding procmail rule:
Reporting through mail becomes more inefficient with the increase of managed servers. Consider logging through Syslog for better scalability, here is a great post about it.