# CPACK_SET_DESTDIR

Boolean toggle to make CPack use `DESTDIR` mechanism when packaging.

`DESTDIR` means DESTination DIRectory. It is commonly used by makefile users in order to install software at non-default location. It is a basic relocation mechanism that should not be used on Windows (see `CMAKE_INSTALL_PREFIX` documentation). It is usually invoked like this:

    make DESTDIR=/home/john install

which will install the concerned software using the installation prefix, e.g. `/usr/local` prepended with the `DESTDIR` value which finally gives `/home/john/usr/local`. When preparing a package, CPack first installs the items to be packaged in a local (to the build tree) directory by using the same `DESTDIR` mechanism. Nevertheless, if `CPACK_SET_DESTDIR` is set then CPack will set `DESTDIR` before doing the local install. The most noticeable difference is that without `CPACK_SET_DESTDIR`, CPack uses `CPACK_PACKAGING_INSTALL_PREFIX` as a prefix whereas with `CPACK_SET_DESTDIR` set, CPack will use `CMAKE_INSTALL_PREFIX` as a prefix.

Manually setting `CPACK_SET_DESTDIR` may help (or simply be necessary) if some install rules uses absolute `DESTINATION` (see CMake `install()` command). However, starting with CPack/CMake 2.8.3 RPM and DEB installers tries to handle `DESTDIR` automatically so that it is seldom necessary for the user to set it.