deb-postinst - package post-installation maintainer script
DEBIAN/postinst
A package can perform several post-installation actions via maintainer scripts, by including an executable postinst file in its control archive (i.e. DEBIAN/postinst during package creation).
The script can be called in the following ways:
After the package was installed.
After the package was triggered. The list of space-separated trigger-names is passed as the second argument.
If prerm fails during upgrade or fails on failed upgrade.
If prerm fails during removal.
If prerm fails during deconfiguration of a package.
If prerm fails during replacement due to conflict.