# Linux Kernel Module Cheat
The perfect emulation setup to study and develop the <<linux-kernel>> v5.9.2, kernel modules, <<qemu-buildroot-setup,QEMU>>, <<gem5-buildroot-setup,gem5>> and x86_64, ARMv7 and ARMv8 <<userland-assembly,userland>> and <<baremetal-setup,baremetal>> assembly, <<c,ANSI C>>, <<cpp,C++>> and <<posix,POSIX>>. <<gdb>> and <<kgdb>> just work. Powered by <<about-the-qemu-buildroot-setup,Buildroot>> and <<about-the-baremetal-setup,crosstool-NG>>. Highly automated. Thoroughly documented. Automated <<test-this-repo,tests>>.

#### 38.13.4. Buildroot build variants

Allows you to have multiple versions of the GCC toolchain or root filesystem.

Analogous to the Linux kernel build variants but with the `--build-id` option instead:

    ./build-buildroot
    git -C "$(./getvar buildroot_source_dir)" checkout 2018.05
    ./build-buildroot --buildroot-build-id 2018.05
    git -C "$(./getvar buildroot_source_dir)" checkout -
    ./run
    ./run --buildroot-build-id 2018.05