Troubleshooting

This page contains some tips to help you resolve issues with thumbnails.

First thing to check is if the format is detected properly.

file --mime-type <FILE>

EPUB

Sometimes epub's are not packed properly, they're essentially just zip files.

Let's extract contents first.

unzip <FILE> -d tmp && cd tmp

Create mimetype file inside.

echo -n 'application/epub+zip' > mimetype

Two things are essential in repacking process:

• mimetype must be the first file that goes into archive.
• Cover image must be the first image that goes into archive.

zip -rX <FILE> mimetype META-INF OEBPS/Images/cover.jpg OEBPS <...>

If OEBPS directory doesn't exist, use whatever your file was packaged with.