Disclaimer: This is not a secret procedure, all the information is available on EMC Powerlink. But remember, in a normal situation, this procedure performs the EMC support. You do it at your own risk.
This post is a synthesis of knowledge from the Internet. The entire procedure lasts one minute and is completely safe. However, it requires the input mode SE (system engineer) and later to the Data Domain Bash. The main requirement is to also have an active user, other than the sysadmin, with administrator privileges. If you do not have such user that you must turn for help to EMC Support (sorry).
We start from the log in via SSH to Data Domain, then enter the command sequence:
system show serialno
priv set se
(Password is SN)
At this point, we are in the bash as the root user and we can, using the passwd command, to change your sysadmin password. The whole procedure looks like this:
This is all.