The root user and at least one normal user can be added during install using data supplied in the control file. User data and passwords (encrypted or in clear text) are part of the configure resource in the control file.

At least the root user should be configured during auto-installation so you can login after the installation is finished. It will also ensure nobody else can login to the system (in case the password is not set).

The two users in the following example are added during system configuration.

...
   <users config:type="list">
      <user>
         <username>root</username>
         <user_password>password</user_password>
         <encrypted config:type="boolean">true</encrypted>
         <forename/>
         <surname/>
      </user>
      <user>
         <username>nashif</username>
         <user_password>password</user_password>
         <encrypted config:type="boolean">true</encrypted>
         <forename>Anas</forename>
         <surname>Nashif</surname>	  	
      </user>
   </users>
...

The last example shows the minimal information required for adding users. Additional options are available for a more customized user account management. The data in /etc/default/useradd is used to determine the home directory of the user to be created as well as other parameters.