The MIME database is a collection of files that include the following information:
The set of known MIME types
The method for determining the MIME type of a file
Meta information regarding a MIME type
The MIME database is created from the set of files located in the $XDG_DATA_HOME/mime and $XDG_DATA_DIRS/mime directories. If the environment variables are not set, then the default values are ~/.local/share and /usr/local/share:/usr/share respectively.
This guide uses <MIME> to refer collectively to these directories. If conflicting information for the same MIME type is found, the information in the file that is found first takes precedence.
For example, assuming default paths for the environment variables , an instruction to load the <MIME>/text/plain.xml file, loads the following files:
~/.local/share/mime/text/plain.xml
/usr/local/share/mime/text/plain.xml
/usr/share/mime/text/plain.xml