Showing affected nodes before uploading cookbooks
You tweak a cookbook to support your new server and upload it to your Chef server. Your new node converges just fine and you're happy. Well, until your older production server picks up your modified cookbook during an automated Chef client run and throws a fit. Obviously, you forgot that your old production server was still using the cookbook you tweaked. Luckily, there is the knife preflight command, which can show you all the nodes using a certain cookbook before you upload it to your Chef server.
Getting ready
For the following example, we assume that you have multiple servers with the ntp cookbook in their run list (either directly or via roles).
Use Chef to install the knife-preflight gem. It contains the preflight plugin extending knife with additional commands:
mma@laptop:~/chef-repo $ chef gem install knife-preflight Fetching gem metadata from https://rubygems.org/ ...TRUNCATED OUTPUT... Installing knife-preflight (0.1.8)
