I recently caught a question on Twitter from Steve Jin, asking if anyone knew how to force an ESXi host to expire it’s trial license for testing purposes.
This got me thinking a bit, and I initially thought the obvious solution would be to set the host’s system clock forward by 60 days for example. I quickly remembered though, that ESXi hosts always seem to count time toward their trial license time based on the number of hours they are powered up for. If you power your host down for a month, and power it back up again, you’ll still have the same amount of time left over on your trial license.
So the next thing I thought, was if I were building a product and protecting it with licensing, surely I would try to prevent people from tampering with the license files. So if someone were to tamper with a license, I could immediately deactivate it, or expire it. This is where I got the idea that worked for Steve’s use case – finding the license.cfg file, and entering some invalid data.
The exact solution, as Steve found, was to find the etc/vmware/license.cfg file on your ESXi host, and tamper with <epoc> the entry, causing the license to become invalid. At this point, any remaining trial license time is invalidated and your license enters an expired state.
— Steve Jin (@sjin2008) July 3, 2014
Change the string highlighted above to some random entry, save the file, then reboot your host. Once rebooted, your trial period will have expired!
This could be really useful in some circumstances. Perhaps there is no clear documentation on how a host running VMs in your environment would react if a trial license expired, or you wanted to know how your 3rd party backup software would react to unlicensed hosts. Being able to easily test an expired license scenario can be really handy!