squashfs work

create squashfs-tools package and create bootable squashfs image. The image contains one single ext4 partition, which in turn contains the bootloader, kernel, squashfs root file and the initramfs.
Boot process is the following:
  bootloader loads kernel to memory
  kernel loads /init inside the initramfs
  initramfs /init mounts the squashfs to / and pivots the root to it