Ohai is the tool used by a Chef client to find out everything about the node's environment. During a Chef client run, Ohai plugin populates the node object with all the information it found about the node such as its operating system, hardware, and so on.
It is possible to write custom Ohai plugins to query additional properties about a node's environment.
In this example, we will see how to query the currently active firewall rules using iptables and make them available as node attributes.
Make sure you have iptables installed on your node. See the Managing firewalls with iptables recipe in Chapter 7, Servers and Cloud Infrastructure.
Make sure you have the chef-client cookbook available:
Add the
chef-clientcookbook to yourBerksfile:mma@laptop:~/chef-repo $ subl Berksfilecookbook 'chef-client'
Add the
chef-clientcookbook to your node's run list:mma@laptop:~/chef...