This Raspberry Pi's official document details the procedures of how to cross-compile new Linux Kernel for Raspberry Pi. Some commands in this document which are shown below, however, I can hardly understand.
For Pi 2:
$ cd linux
$ KERNEL=kernel7
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcm2709_defconfig
- What dose
KERNEL
env stand for? - Why we need to set
KERNEL
tokernel7
? - Also, what doese
make bcm2709_defconfig
do?