Create a .tgz with theese files. Name it KoboRoot.tgz and put by usb cable in your Kobo Glo HD at .kobo/KoboRoot.tgz.
You will be able to execute scripts from images with fmon (see mnt/onboard/.kobo/fmon/). You also will be able to telnet as root to your Kobo Glo HD (no password initially) and upload files through ftp.
A script is able to update the Kobo Glo HD database after ftp uploads: it emulates the connection of a usb cable; click connect when it asks and wait a while to update the sqlite data with your new e-books. You have to choose an image and put it into /mnt/onboard/update.png (see mnt/onboard/.kobo/fmon/update.sh)
Enjoy it ;)