anchor.diff:          , createHome ? false
           , useDefaultShell ? false
           , password ? null
  +        , isSystemUser ? true
           }:
  -        { inherit name description uid group extraGroups home shell createHome password; };
  +        { inherit name description uid group extraGroups home shell createHome password isSystemUser; };
   
       in map addAttrs (defaultUsers ++ config.users.extraUsers);
   
  
positive.code: 
    # Note: the 'X' in front of the password is to distinguish between
    # having an empty password, and not having a password.
    serializedUser = u: "${u.name}\n${u.description}\n${toString u.uid}\n${u.group}\n${toString (concatStringsSep "," u.extraGroups)}\n${u.home}\n${u.shell}\n${toString u.createHome}\n${if u.password != null then "X" + u.password else ""}\n";
    serializedGroup = g: "${g.name}\n${toString g.gid}";
    
    # keep this extra file so that cat can be used to pass special chars such as "`" which is used in the avahi daemon
  
negative.code:             read shell
              read createHome
              read password
              read isSystemUser
  
              if ! curEnt=$(getent passwd "$name"); then
                  useradd ''${isSystemUser:+--system} \
                      --comment "$description" \
                      ''${uid:+--uid $uid} \
                      --gid "$group" \
  