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To verify that the puppet7-master works you can start to direct puppetrequests to it. Update for some nodes in your environment the profile::puppet::hostname to the puppet7 master and see everything works as expected. Remeber to deploy the needed environments to it first.
Point the rest of the puppet-masters (including the CA) to the puppet7-master, add the two following keys to hiera node-files, and then run puppet to upgrade the puppet-agent:
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