Wow, this one stumped me for the better part of 12 hrs… So Puppet (the Ruby Gem) uses SSL certificates to authenticate to the Puppet Master.  I kept receiving the warning listed in the title of this post no matter how I altered my configs. Here’s the short version: Determine what Fully Qualified Domain Name is being used by the PuppetMaster to created the signing cert.  On my virtual platform this ended up being the hostname Add that hostname/FQDN and it’s IP address to your PuppetClient’s /etc/hosts like so: 173.999.999.999    hostname Now start up the PuppetMaster Server with the following command # puppetmasterd --verbose --no-daemonize Now invoke the puppet client like so: puppet agent --no-daemonize --verbose --server=HostnameOfServer Finally, now that we know it’s working well edit the /etc/puppet/puppet.conf on Puppet Client so that you have a server entry in the [main] section: [main] server=HostnameOfServer Tada!   Source of partial answer: Puppet hostname doesnt match server certificate - Server Fault.