Can't flash smaller root-fs through dfu-util?

[andy selby]

> > If you upload rootfs image that is smaller that previous one it
> > won't work - you need to attach to bootloader, erase NAND and then
> > upload your rootfs first:
> >
> > cu -l /dev/ttyACM0
> > GTA01Bv3 # nand erase rootfs
> This *should* help but I am trying to understand why dfu-util can't
> do that? And what do I do if I have no serial interface? Does this
> mean I can't ever again flash a (smaller) rootfs?

Just type
screen /dev/ttyACM0
into any pc while the device is in u-boot mode attached by a usb
cable, that will give you the GTA01Bv3 prompt