Creating minimal linux test environment

Building Kernel with default x86_64 configuration

• create default kernel build configuration using existing defconfig make ARCH=x86 x86_64_defconfig The file .config is created in linux root directory. It can be still modified with make menuconfig

• build kernel image make -j8 As a result we obtain a vmlinux binary which is a stand-alone monolithic ELF image. This binary contains no unresolved external refeces. Despite this file was found at the top-level kernel directory. Very few platforms boot this image directly including qemu emulator. In order to boot qemu we need to use bzImage compressed kernel file. From: arch/x86/boot/bzImage

• preparing initramfs

I prepared a simple initramfs just to make kernel fully boot into shell. As a shell it was used busybox (just remember to check if that's a standalone version "static") The directories were created in compliance to FHS (Filesystem Hierarchy Standard). And I finally I add an init script which initializes busybox and mount pseudo-file system like sysfs procfs dev and tmp.

• running qemu By running appropriate qemu command: qemu-system-x86_64 -kernel ./arch/x86/boot/bzImage -nographic -append "console=ttyS0" -initrd initrd

In order to exit qemu run: Ctrl-a x

Full work can be found here: test_environment