I'd like to have certain file extensions to be opened with some specific programs.What are the files the edit ? I have found in /usr/share/appplications/default.list but it doesn't work.
How to change the default program for a specific file extension system-wise in kde or xfce?
files;kde;xfce;freedesktop
Have a look at the file $HOME/.local/share/applications/defaults.listThere is a section [Default Applications] to specify the programs for particular mime types. You can add for example:application/x-debian-package=gdebi.desktopThe .desktop files can be found in /usr/share/applications/ or you can create your own files under $HOME/.local/share/applications/. To find out the mime type of the files, runfile --mime-type <some_file>Alternatively, in KDE one can accomplish the same in GUI in File Associations inside System Settings.To register a MIME type for an extension see freedesktop.org - AddingMIMETutor and stackoverflow - Register file extensions / mime types in Linux.