The default admin password in Enterprise Server 2.1 is changeit. To avoid problems when logging in to the Enterprise Server after upgrading from 8.2, do one of the three following things:
Change the 8.2 admin password to changeit before performing the upgrade.
Do not accept the default admin password during the upgrade process, but instead explicitly enter the password you want to use.
Log in to Enterprise Server 2.1 with the default password, and then immediately change it.