The user accounts and GRUB passwords can be changed on the database servers. The default user accounts on the database server are root, and the software owner account. Typically the software owner account is oracle or grid.

• Changing the User Account Password on the Database Server
  As the root user, use the passwd command to change operating system user passwords.
• Changing the GRUB Account Password on the Database Server
  Use the host_access_control script to change the GRUB account password on database servers.