Customers who upgrade to Chef Server 12 may notice the following message displayed at the top of the Chef Manage console:
This installation is managing 26 nodes, but is only licensed for 25. Please upgrade now to ensure proper licensing.
Most importantly, Chef Server 12 does not take or use license keys. The Chef Server Core will not limit nodes functionality in any way. The Chef Manage interface will only provide a "nag message" if your node count exceeds a certain value (25 by default).
Licensed customers are recommended to change that value by setting the following attribute in the /etc/opscode/chef-server.rb file:
license['nodes'] = number_of_licensed_nodes
where number_of_licensed_nodes is an integer value that matches your Chef Premium Subscription node count.
Then perform a 'chef-server-ctl reconfigure' and 'chef-manage-ctl reconfigure' for the setting to take effect. In Tier and HA Chef Server topologies, these steps must be performed on all of the Chef servers.