First of all you need to install the toolchain (cross compiler, linker, etc) on your Linux Ubuntu PC following this article (tested on Ubuntu 16.04):
The GitHub repository is available here:
Clone this repository in your Linux PC by typing:
~$ git clone https://github.com/linux4sam/at91bootstrap.git
Move inside the new at91bootstrap directory and set the right configuration to use with the roadrunner board by typing:
~/at91bootstrap-3.8 $ make sama5d2_roadrunner_defconfig
If you want to take a look to the at91bootstrap configuration run:
~/at91bootstrap-3.8 $ make menuconfig
To launch the compilation type:
~/at91bootstrap-3.8 $ make CROSS_COMPILE=arm-linux-gnueabi- ...
The compilation result is this binary file:
A symbolic link is generated automatically during the at91bootstrap compilation so you can refer to it as at91bootstrap.bin.
Actually the RoadRunner SOMs mount the Microchip SAMA5D27 revision B that can boot boot directly from the QuadSPI memory but not from the MicroSD.
To transfer at91bootstrap.bin on the QuadSPI follow this guide: