1. Access the console of both controllers through a serial connection
At startup, press Ctrl-C to access the startup menu
Shut down all nodes (this can be done by shutting down the chassis PSU or uninstalling the controller), and then restart
From the startup menu, select option (4) : Clean configuration and initialize all disks
Clear all configurations and data and reconfigure the device
2. If you want to keep the previous configuration, only change the current password:
Console access to both controllers via serial connection
Shut down a node (this can be done by shutting down the chassis PSU or uninstalling the controller) and then restart
At startup, press Ctrl-C to access the startup menu
Select option (3) from the startup menu: Change password.
Enter your user name, and then enter a new password
You will be returned to the startup menu. Select option (1) for normal boot
Below is the official operation link of the specific operation, you can refer to:
https://kb-cn.netapp.com/on-prem/ontap/Ontap_OS/OS-KBs/How_to_reset_admin_password_from_boot_menu_in_ONTAP