Originally Posted by kovidgoyal
Do any epub reading systems actually insist on the mimetype file being first?
Probably not. In principle the Unix file command should be able to identify the file as an ePub if mimetype is first, but under Fedora 9 all I get is "Zip archive". Even FBReader (which looks inside .pdb files for the file type) just keys on the .epub filename extension.
For Linux, the following single command works:
zip -vur Author_Title.epub mimetype *
The "*" wildcard also includes mimetype but it still ends up 1st in the file and uncompressed. The "-u" does not seem necessary, but it is supposed to only overwrite existing files in the archive with newer versions.