This seems to be a pretty commonly Google question, but one for which there are no answers.

http://www.linuxquestions.org/questions/linux-software-2/firefox-download-mime-types-378902 http://www.birkit.com/content/kubuntu-linux/internet/firefox/fix-file-associations-in-firefox.html

Being three links amongst the many.

The gist of what I want to accomplish is to have Firefox understand the file associations I download without me having to manually map all of them myself. Gnome knows the file extensions, so I would have expected that Firefox could just use the already-known file mappings there to open the right stuff (as I presume Chrome does). But it doesn't. At least not for me, using Firefox 4, and not by default. When I click on a downloaded file right now, Firefox always has to ask me what application should be used to open the file.

A handful of Google results tell me that I can reassociate my file extensions by deleting ~/.mozilla/firefox/[profile name]/mimeTypes.rdf, but while deleting that file does in fact result in a new mimeTypes file being generated, the new mimeTypes is just as barren as the old one had been.

Based on the amount of unanswered Qs on the Googlesphere, I know this is a very common problem for Ubuntu users, but it seems to be one for which nobody has chimed in with a good solution. Maybe Superuser can finally be the panacea for us all?