update-mime

update-mime-database [OPTIONS] DIRECTORY

-v, --verbose
    Enables verbose output, showing detailed progress during cache generation.

-n, --no-fork
    Prevents the command from forking, useful for debugging purposes.

DIRECTORY
    The path to the directory containing MIME XML definition files, typically /usr/share/mime.

update-mime-database (the command usually invoked by update-mime) is a utility that rebuilds the cache files used by the shared-mime-info system.

This system provides a centralized collection of common MIME types, enabling applications (like file managers, web browsers, or text editors) to correctly identify and handle various file formats. When new applications are installed or new MIME type definitions are added to the system (typically in XML files within directories like /usr/share/mime), this command scans these definitions and compiles them into efficient binary cache files (commonly mime.cache and mimeinfo.cache).

These cache files allow for rapid lookup of file types based on their extensions or magic numbers, ensuring applications can quickly determine how to open or process a file. Users rarely need to run this command manually, as it is usually triggered automatically by package managers after installing software that introduces new MIME types.

The command typically needs root privileges to update the system-wide MIME database in locations like /usr/share/mime.

update-mime is often a symlink or wrapper script for update-mime-database, which is the primary utility for this task.

Manual execution is rarely necessary as package managers usually trigger it automatically upon installing or updating software that provides new MIME definitions.

MIME (Multipurpose Internet Mail Extensions) types are crucial for operating systems and applications to understand the format and content of files. For example, a web browser uses MIME types (e.g., application/pdf, image/jpeg, text/html) to determine how to display or handle downloaded content, ensuring the correct viewer or application is launched.

The generated cache files, typically named mime.cache and mimeinfo.cache, are usually located within the DIRECTORY specified, such as /usr/share/mime. These binary files are optimized for fast lookups by applications.

The update-mime-database command is an integral part of the shared-mime-info project, which emerged to standardize MIME type definitions across various Linux desktop environments like GNOME, KDE, and XFCE.

Before its widespread adoption, different desktop environments often had their own, sometimes conflicting, methods for handling MIME types, leading to inconsistencies. The shared-mime-info project aimed to provide a single, centralized, and extensible repository for MIME data.

This command was developed to efficiently compile these XML-based definitions into a quickly searchable binary cache, improving system performance and consistency.

xdg-mime(1), file(1), shared-mime-info(7)