The default usernames are root on 7mode, admin on cDOT. From manufacturing there is no password set. The first time a 7mode system is booted it will load to a setup script. Similarly in cDOT it will boot to either node setup or cluster setup, depending on the code version installed. In a few corner cases, a partially configured cDOT system will boot to a login screen, username admin with no password.
The one exception would be a "factory configured cluster", which would have included the password in the documentation but I think its been some time since any of those shipped.
If you've lost the password you can reset it via the serial port from the boot menu (requires a reboot).
If this post resolved your issue, help others by selecting ACCEPT AS SOLUTION or adding a KUDO.