All a.out shared object libraries required on the SunOS 4.x release, except for the SunOS and the Open Windows libraries, must be moved to Solaris 2.x or mounted. These libraries can be copied to the /usr/4lib directory. These libraries must retain the same major and minor version numbers they had in the SunOS 4.x release.
Environment variable LD_LIBRARY_PATH
Directories specified at link-time with the -L dir option to ld(1)ld(1)
Default directories: /usr/4lib:/usr/lib:/usr/local/lib
The /usr/4lib directory did not exist in SunOS 4.x. It is provided as a location for SunOS 4.x a.out libraries. This directory has been added to the default search rules so that compatibility package users can store their SunOS 4.x libraries there and be assured that the run-time linker will find them.