A quick tour into the bootloader
As stated at the beginning of this chapter, using the serial console, we can get access to the bootloader.
Actually, all the developer kits presented in this book have two bootloaders: a pre-bootloader or Secondary Program Loader (SPL), named MLO for the BeagleBone Black, boot.bin for SAMA5D3 Xplained, and SPL for the Wandboard, which initializes the hardware components, such as the RAM and some mass storage devices, and bootloader named U-Boot for all boards, which is the real bootloader that initializes almost all the peripherals and has support for, among other things, booting over network and a scriptable shell through which basic commands can be given. Now the one million dollar question is: why should a developer be able to manage the bootloader too?
Well the answers are more than one; however, the most important ones are:
- By passing a well-formed command line to the kernel, we can change some functionalities in the running filesystem.
- From the bootloader...
