You are using Microsoft Internet Information Services IIS to provide firmware updates via HTTP for your IGEL thin clients (Windows or Linux based). When starting an update process you will receive an error message such as "File not available" or "File is not an archive" and the update process will terminate unsuccessfully.
IIS does not offer files with unknown MIME types for download and blocks the request coming from the thin client.
Make sure all files provided in the firmware update are added to the list of MIME types in IIS. Proceed as described in this Microsoft support document.
Add a new MIME type for files of extension (wildcard) '*' with a type of 'application/octet-stream'. This will provide a default MIME type for all files that don't already have one and bypass the blocking.
Microsoft does not recommend setting a wildcard enabling IIS to send out any kind of file for security reasons. You may add every single file extension of your firmware update files to the list of MIME types instead.
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