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When running update-mime-database - usually automatically launched by apt-get - why do I reliably get complaints like:

Unknown media type in type 'all/all'
Unknown media type in type 'all/allfiles'
Unknown media type in type 'uri/mms'
Unknown media type in type 'uri/mmst'
Unknown media type in type 'uri/mmsu'
Unknown media type in type 'uri/pnm'
Unknown media type in type 'uri/rtspt'
Unknown media type in type 'uri/rtspu'
Unknown media type in type 'fonts/package'
Unknown media type in type 'interface/x-winamp-skin'

It doesn't seem to be hurting anything, but chronic errors during updates risk obscuring an error that I do care about.

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Actually you can fix it simply by doing

sudo rm /usr/share/mime/packages/kde.xml 
sudo update-mime-database /usr/share/mime

Here is a quote from Ana Guerrero in 2008 so you'd think it would be fixed by now.

Those fake mimetypes are installed by kdelibs with the file /usr/share/mime/packages/kde.xml since long time ago. They are kept in kde4libs.

In a recent version, update-mime-database became verbose about this unknown types, and that is why you get this error when you update stuff and then update-mime-database is run. It is unlikely to be changed.

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Still needed in 15.10 ;-( I have followed this, forgot how to do it, searched, found it, and did it again. lather rinse repeat. Each time, although I did not remember where the files and what the commands were, I found this post and have visited and used it 3 times (stats from google search on chrome). I used this search string, and add it here so that it rises from second to first (How to remove warnings like `Unknown media type in the set of answers. ubuntu mime-types all/all unknown media type – ElderDelp Nov 17 '15 at 20:28

That's a problem with update-mime-database and the MIME standard itself. Originally it was supposed to be extensible. But the IETF dumbed it down, and no new major mime types are registered (application/* is used as undifferentiated catch-all). The reasoning/surmise behind that being, that few tools are designed to work correctly with new MIME types.

Now update-mime-database at least doesn't fall over when it sees pseudo classifiers like uri/ and fonts/ or interface/. So I assume it only complains because other apps might actually trip over them. strings gave me following list of probably built-in list of "safe" MIME types:

  • text
  • application
  • image
  • audio
  • inode
  • video
  • message
  • model
  • multipart
  • x-content
  • x-epoc

Meaning it would nag over any other x- or x. and vnd. or prs. major mime types. Curiously inode/ is anything but an official media type.

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Thanks for this valuable comment. It's very useful to know that custom-named mimetypes won't work. Tried creating a mimetype named 'comprovante/biblioteca' and that's why it wasn't working on recent Ubuntu / Linux Mint versions. – Leonardo Montenegro Dec 4 '14 at 18:49
up vote 2 down vote accepted

It appears that there are a pile of KDE libraries that bring in these otherwise Gnome unfriendly mime-type definitions. In my case, the libraries were added as dependencies to a KDE application package that I later uninstalled.

To remove the pile of KDE libraries and their associated /usr/share/mime entries, I used:

sudo apt-get purge kdelibs-bin kdelibs-data 
sudo apt-get autoremove --purge
sudo update-mime-database /usr/share/mime

Do be careful that the first command does not force removal of a package you need before you confirm the removal. Getting rid of kdelibs-bin will then make a large set of packages unneeded and ready for autoremove.

I found the basis for this fix in an old bug report for Intrepid Ibex.

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