You'll need an access to the serial console to achieve this, the JTAG module is OK.
* To connect to the bootloader, proceed exactly like for the [[Marvell Plug Computer|Sheevaplug: http://wiki.amahi.org/index.php/Marvell_Plug_Computer ]
* Reset the GuruPlug.
* At the terminal, press enter a couple of seconds after boot to prevent it from booting using the onboard flash (Ubuntu). You should end up with a prompt.