CPACK_PACKAGING_INSTALL_PREFIX ------------------------------ The prefix used in the built package. Each CPack generator has a default value (like /usr). This default value may be overwritten from the CMakeLists.txt or the cpack command line by setting an alternative value. e.g. set(CPACK_PACKAGING_INSTALL_PREFIX "/opt") This is not the same purpose as CMAKE_INSTALL_PREFIX which is used when installing from the build tree without building a package.