Theory

- mkinitcpio
  It is used to generate initrd (initial ramdisk). : The initial ramdisk is in essence a very small environment (early userspace) which loads various kernel modules and sets up necessary things before handing over control to init .
   
  it is a scheme of loading temporary file system into memory as a part of linux startup process. Very useful in case system not starts and to edit or fix it it falls to initrd fallback