Step 1 – cloning the kernel source tree

We arbitrarily select a staging folder (the place where the build happens) for the kernel source tree and the cross-toolchain, and assign it to an environment variable (so as to avoid hard-coding it):

1. Set up your workspace. We set an environment variable as RPI_STG (it's not required to use exactly this name for the environment variable; just pick a reasonable-sounding name and stick to it) to the staging folder's location – the place where we shall perform the work. Feel free to use a value appropriate to your system:

export RPI_STG=~/rpi_work
mkdir -p ${RPI_STG}/kernel_rpi ${RPI_STG}/rpi_tools

Do ensure you have sufficient disk space available: the kernel source tree takes approximately 900 MB, and the toolchain around 1.5 GB. You'll require at least another gigabyte for working space.

2. Download the Raspberry Pi kernel source tree (we clone it from the official source, the Raspberry Pi GitHub repository for the...