The ESXi 6 evaluation license is valid for 60 days and a free license can be obtained from VMware at any time.
Enable SSH and log in to the host.
Remove the current license with the command below in the terminal
rm -r /etc/vmware/license.cfg
Copy the new trial license, which is already available on the host
cp /etc/vmware/.#license.cfg /etc/vmware/license.cfg
Restart ESXi services
/etc/init.d/vpxa restart
Restart the HOST (Virtualizer)
Automating the process
You can add a script in CRON to always run before the next expiration, this way you keep the free license valid for another period of 60 consecutive days.
First create the script (reset-eval.sh) somewhere accessible to ESXi
#!/bin/sh
## remove license
echo 'Removing License'
rm -r /etc/vmware/license.cfg
## get a new trial license
echo 'Copying new license'
cp /etc/vmware/.#license.cfg /etc/vmware/license.cfg
## restart services
echo 'Restarting VPXA'
/etc/init.d/vpxa restart
