These directory contains the sources to build the resolver portion which is compiled into every program that uses the name server. There are two options. You can simply type 'make install' which will build and install /usr/lib/libresolv.a or you can 'cp *.c' to /usr/src/lib/libc/net, edit /usr/src/lib/libc/net/Makefile and install a new version of /lib/libc.a. The first means you must compile programs 'cc ... -lresolv', the second just replaces the old gethostbyname() and gethostbyaddr() with routines to access the nameserver. In either case, most programs that use the gethostby...() routines will work correctly.