How do I use GNU Chess 5 with XBoard?
By default, XBoard still tries to use GNU Chess 4 by running the command “gnuchessx”. That’s why if you don’t have GNU Chess 4, you get the error message “Failed to start first chess program gnuchessx on localhost: gnuchessx: No such file or directory.” If you have GNU Chess 5, the command should be “gnuchess xboard” instead.