Usually it will find something in the onboard eMMC and boot from there. In default mode (S2 not pressed) it tries to boot from The BeagleBone Black provides by alternative boot sequences which are selectable by the boot switch (S2). The AM335x processor on the BeagleBone Black has many configurable options where it can boot from which are all documented in Chapter 26 of the AM335x ARM® Cortex™-A8 Microprocessors Technical Reference Manual. As we later want to change the Linux Kernel itself we need to know how it is started by the BeagleBone.
Understanding the boot up mechanism of the BeagleBone Black is important to be able to modify it.
