update-mime

update-mime-database <directory>

<directory>
    The directory containing XML files with MIME type definitions. This is typically a directory like /usr/share/mime.

The update-mime-database command updates the shared MIME information database. This database is used by applications to determine the MIME type of files based on their content and extension. It scans a directory tree for XML files conforming to the shared MIME info database specification. These XML files contain information about MIME types, their associated file extensions, and other metadata. The command then compiles this information into a binary database file, which is used by applications to quickly determine the MIME type of a file.
Running this command is essential after installing new applications or updating existing ones that provide new MIME type definitions. Without updating the database, applications may not recognize new file types correctly. The command should be run with administrative privileges as the target databases are generally located in system directories.

Running update-mime-database requires write access to the target database directory, typically requiring root privileges. Incorrectly formatted XML files can cause the command to fail. Using outside sources for xml based files can introduce security problems.

The primary purpose of update-mime-database is to ensure that applications have access to an up-to-date and accurate MIME type database, enabling them to correctly handle a wide variety of file formats.

xdg-mime(1), mimeopen(1)