Originally Posted by BensonBear
I believe someone has posted somewhere that if you look at the most recent files in the images directory you will be likely to be able to tell which file the kobo was on when it hung.
Sorry for not looking for the post... I no longer use the Kobo software except as a hook for my own pdf and epub renderers and database manager.
(btw, to clarify: large red font not in my original post but I assume added for emphasis in the quotation...)
That might have been the case with the 1.9.x firmware. From 2.0.0, the cover images are generated the first time they are needed.
I did some experimenting recently about the processing order. It seems to be alphabetical. It is definitely alphabetical within a directory. When multiple directories are involved, it seems to be alphabetical as well. I haven't done a proper test on that, just checked the timestamps in the database after using SD card with about 500 books on it.