The variable (17.7) ngbehavior sets the compatibility mode. 'all' is set as the default value. 'spice3' as invoked by the command

set ngbehavior=spice3

in spinit or .spiceinit will disable some of the advanced ngspice features. 'ps' will enable including a library by a simple .lib <lib_filename> statement that is not compatible to the more comfortable library handling described in Chapt. 2.7.