Linux: Thumbnailers and MIME Types (thumbnail / mimetype) - creating thumbnail images for file manager

How to detect the MIME type of a file

• Right-click properties within file manager
• xdg-mime query filetype <filename>
• file --mime-type -b <filename>

References

• How to create custom thumbnailers for nautilus, nemo, and caja
• Adding MIME types in Ubuntu Linux
• Storage of file associations in Ubuntu Linux
• Desktop specifications