deb-preinst - package pre-installation maintainer script
DEBIAN/preinst
A package can perform several pre-installation actions via maintainer scripts, by including an executable preinst file in its control archive (i.e. DEBIAN/preinst during package creation).
The script can be called in the following ways:
Before the package is installed.
Before removed package is upgraded. The new-version is passed only since dpkg 1.18.5.
Before the package is upgraded. The new-version is passed only since dpkg 1.18.5.
If postrm fails during upgrade or fails on failed upgrade.