If for some reason the iDRAC username and login have been lost or are unknown, the password can be reset using ipmitool
NOTE: The previous username and password does not need to be known for this process to work.
ipmitool user list 1
ipmitool user set password 2 <new_password>
You can also use racadm to reset the password and perform other configuration tasks. See the following article for details: