Getting started with CFEngine part 4 (writing the first policy)

Ok, so we've installed the policy server & client & tested out some of the commands.
Now lets write a policy.

The first policy would have to say 'hello world'.

Given below is a small policy file my.cf:

[root@dockertest tmp]# cat my.cf
body common control
{
bundlesequence => { "my_test" };
}
bundle agent my_test{
 files:
  linux::
   "/tmp/hello-world"
     create => "true";
}

The only mandatory element in this section is bundlesequence, which tells CFEngine which bundles  to execute and in which order. For the above example policy, we will have a single bundle my_test executed:

body common control
{
bundlesequence => { "my_test" };
}

The example says to create a file /tmp/hello-world on all Linux hosts.

To run a syntax check run the following command:

[root@dockertest tmp]# cf-promises -f ./my.cf
[root@dockertest tmp]#

To execute the policy type:

[root@dockertest tmp]# cf-agent -KI -f ./my.cf

    info: Created file '/tmp/hello-world', mode 0600

[root@dockertest tmp]#

[root@dockertest tmp]# ls -l /tmp/hello-world

-rw-------. 1 root root 0 Apr 24 13:52 /tmp/hello-world

[root@dockertest tmp]#

To run the policy on a distributed system:

By default cf-serverd will serve policy from the /var/cfengine/masterfiles directory. Upon updates, cf-agent will be notified and start to download these before executing them locally.

This means that by default you should store all your policies in the /var/cfengine/masterfiles directory on your policy server. So, now let’s copy our policy to this location:

cp /tmp/my.cf /var/cfengine/masterfiles/my.cf

1. Modify the /var/cfengine/masterfiles/promises.cf file and insert the bundle name my_test in the bundlesequence in body common control. 

2. Include the my.cf  in the inputs section of body common control in promises.cf. 

Save the file, and you are done!