A user is configuring a server OS. Which of the following should the user do after setting up the system?

Default usernames and passwords are well-known and represent a significant security vulnerability, as attackers can easily use them to gain unauthorized access to the server. Changing them immediately hardens the system against common attack vectors.

Synchronizing administrative logins with other servers on the domain is part of identity management in an enterprise environment, but changing default credentials is a more immediate and fundamental post-setup security step for a newly set up server.

Disabling the administrator password would leave the administrator account completely unprotected, which is a severe security risk and never a recommended action.

Clearing the password complexity database would remove rules requiring strong passwords, making the system less secure by allowing users to set weak, easily guessable passwords.