[gentoo-portage-dev] manual uninstall

[Lanza Fabrizio]

 Hi,
I need to manually uninstall a package (without emerge --unmerge). How
do I tell emerge that a package is not installed (even if it is)? (I
basically need to force a reinstall, for a catalyst issue.)
 
 Another good question is: how does portage know that a package is
actually installed?
 
 Thank you.