Using why-run mode to find out what a recipe might do

why-run mode lets each resource tell you what it would do during a Chef client run, assuming certain prerequisites. This is great because it gives you a glimpse of what might really happen on your node when you run your recipe for real.

However, because Chef converges a lot of resources to a desired state, why-run will never be accurate for a complete run. Nevertheless, it might help you during development while you're adding resources step-by-step to build the final recipe.

In this section, we'll try out why-run mode to see what it tells us about our Chef client runs.

Getting ready

To try out why-run mode, you need a node where you can execute the Chef client and at least one cookbook available on that node.

How to do it…

Let's try to run the ntp cookbook in why-run mode:

1. Override the current run list to run the ntp recipe in why-run mode on a brand new box:

   user@server:~$ sudo chef-client -o 'recipe[ntp]' --why-run
   ...TRUNCATED OUTPUT......