Comment 3 for bug 820578

Reopening and assigning to Michael Casadevall, as he knows what the issue is.

The problem is the netinstall img file is only 10M, and unless the SD card is repartitioned during install, the flash-kernel step fails due to disk space. Flash-kernel doesn't reformat the SD boot partition, and tries to backup the existing files before copying new ones over. 10M is simply too small for this.