Re: How to exit from linux kernel and return to then grub?

["Lennart Sorensen" <lsorense@csclub.uwaterloo.ca>]

On Sun, May 18, 2014 at 01:33:15PM +0800, Z C wrote:
> If I boot into a linux kernel using a grub command like "linux /vmlinuz;
> inirtd /initrd; boot", how do I shutdown linux itself (but do not power off
> or reboot the computer hardware) and return back to the grub directly?
> 
> What I meant is something equivalent to the "exit" command in most shells:
> If you are within one shell and you enter another shell, then if you want
> to quit the second shell and return back to the first shell, just simply
> type exit. All env variables and commands you previous typed in the first
> shell are completely intact.
> 
> Suppose I am now in the grub shell, and then I boot into a tiny linux
> kernel, say, a busybox shell, then what can I do to exit the second shell
> (i.e. busybox shell) and return to the first shell (i.e. grub shell)? Of
> course I can enter the grub shell again by simply rebooting the hardware,
> but this is not what I want.

Once linux boots, it does not preserve the boot loader in memory (whyever
would it do that?)

If you want to invent a way to load grub using kexec so you can switch
back to grub fropm a running linux system, well have fun, but why bother?
Where is the use?  It is so hard to deal with what the state of all the
hardware is without doing a reset.

-- 
Len Sorensen