anchor.diff:          exec = "${cups}/sbin/cupsd -c ${pkgs.writeText "cupsd.conf" cfg.cupsdConf} -F";
         };
   
  -    services.printing.drivers = [ pkgs.cups pkgs.ghostscript ];
  +    services.printing.drivers = [ pkgs.cups pkgs.ghostscript additionalBackends ];
       services.printing.cupsdConf = 
         ''
           LogLevel info
  
positive.code: 
    cfg = config.services.printing;
  
    # Here we can enable additional backends, filters, etc. that are not
    # part of CUPS itself, e.g. the SMB backend is part of Samba.  Since
    # we can't update ${cups}/lib/cups itself, we create a symlink tree
  
negative.code:   # cupsd.conf tells cupsd to use this tree.
    bindir = pkgs.buildEnv {
      name = "cups-progs";
      paths =  cfg.drivers;
      pathsToLink = [ "/lib/cups" "/share/cups" ];
      postBuild =  ''
        ${cfg.bindirCmds}
      '';
    };
  