File associations in Linux can be tricky. On my Gnome-based Ubuntu machine, I can associate a filetype by right-clicking a file in Nautilus, and slecting “Open with”. To modify the defaults using config files, this post describes it well. Basically, the two main locations to check out are
~/.local/share/applications/. File associations made using these methods apply to the commands
xdg-open as well.
File associations in the command line is mainly done via MIME types (I think). At least file associations in conkeror, org-mode’s
org-open-at-point (also look at
org-file-app), and the
see commands are done by MIME. MIME handlers are defined in a user’s ~/.mailcap file.
I think this information is enough to modify default apps throughout Linux. Do see this post where I outline how I launch all my files using Emacs’ dired mode. Now I can launch apps more uniformly in Nautlius, Emacs, and on the command line based on configuring default apps.