(Link in title is a complete dialog on the topic)
- As superuser, edit:
/usr/share/applications/mimeinfo.cache
/etc/gnome_defaults.conf
or /etc/gnome/defaults.conf
- As normal user, edit the details in the
MimeType
section in ~/.local/share/applications/[FOO-PROGRAM].desktop
For ridding yourself of the double entries:
http://linux.aldeby.org/get-rid-of-gnome-open-with-duplicate-entries.html