Appendix B: The boot loader; replace dummy exercise (exercise 2)

[nubok]

In "Appendix B: The boot loader" there is a dummy text for the second exercise:

xv6-book/appboot.t

Lines 672 to 673 in a2b9e9a

	.exercise
	something about BIOS lasting longer + security problems

Perhaps you want to replace it by a "real" exercise or (less likely) remove the dummy text of this exercise.