Today i spent hours to search the kernel resources I think I've already got it; bzImage includes two parts, one is initrd/initramfs, another is kernel, they're all in one file. The key is initrd, this is the one customised, Next question is that how to get the initrd source code and how to change,then recompile, I think I need to read more books about Linux kernel knowledges. Cheers. 😄