The source files are typically located in the /etc directory on the master server. However, leaving them in /etc is undesirable because the contents of the maps are then the same as the contents of the local files on the master server. This is a special problem for passwd and shadow files because all users have access to the master server maps and the root password would be passed to all NIS clients through the passwd map. See passwd Files and Namespace Security for additional information.
However, if you put the source files in some other directory, you must modify the Makefile in /var/yp by changing the DIR=/etc line to DIR=/your-choice, where your-choice is the name of the directory you will be using to store the source files. This allows you to treat the local files on the server as if they were those of a client. (It is good practice to first save a copy of the original Makefile.)
In addition, the audit_user, auth_attr, exec_attr, and prof_attr NIS maps should be created from a directory other than the default. Amend /var/yp/Makefile by changing RBACDIR =/etc/security to RBACDIR=/your-choice.