Load bootloader after OS partition loaded?

[Serpreme]

How do i go back to my grub bootloader after i've loaded a partition?
Basically i want to avoid having to power down.
I want to be prompt'd to go back to the selection screen after terminating my OS.
Thanks for any help and for just reading this alone.

[i92guboj]

How do i go back to my grub bootloader after i've loaded a partition?
Basically i want to avoid having to power down.
I want to be prompt'd to go back to the selection screen after terminating my OS.
Thanks for any help and for just reading this alone.

As far as I know grub runs in real mode. And linux runs in protected mode from the start. After entering protected mode is not possible to go back to real mode. So, you need to reboot.

I don't understand what's the big problem with that. Even if that was possible, you'd still have to unload all the services, and then load them back. So, that's the long part anyway.

The closest you can get is to boot a new kernel from the current one using kexec:

Reboot Linux faster using kexec

[Serpreme]

The issue is, when you need 2500 computers to have to reboot a extra time, it generally isnt good. I'm trying to find on my own a way around this.
But i've not had very much luck. I'll look into kexec, it sounds interesting!
Thanks again.

[i92guboj]

The issue is, when you need 2500 computers to have to reboot a extra time, it generally isnt good. I'm trying to find on my own a way around this.
But i've not had very much luck. I'll look into kexec, it sounds interesting!
Thanks again.

Well, let's look at it objectively: to shut off and then on the services can take from 30 seconds to 2 minutes or even more. To get to the grub point after the machine is turned on it's 4 or 5 seconds or even less if you configure your BIOS to do a fast POST. Really, I can't see the advantage in what you intend to do. Because, even if there was a way around, you still need to turn off and then on again all the services, which is -by far far far- the longest part of the boot process.

The same goes for kexec. ALL the services need to be turned off and on. So, the time save is virtually inexistent. The only advantage of kexec is that you don't need to select anything in grub, for the rest, I consider it wasted development time on the kernel devs side. But it's just my humble opinion, of course.

[Serpreme]

If its a smaller kernel i am loading and unloading, i bet it would go fast enough.
Basically i need a script to run , then load a OS.
Currently Grub legacy doesn't support this i believe, so i'm stuck with the boot once, reboot and boot into the OS i want. This is just an option i'm going to look into.
It may be slower as you say, but at least i looked into it. And thanks again, the more and more i look into it, the better it looks.

[i92guboj]

If its a smaller kernel i am loading and unloading, i bet it would go fast enough.
Basically i need a script to run , then load a OS.
Currently Grub legacy doesn't support this i believe, so i'm stuck with the boot once, reboot and boot into the OS i want. This is just an option i'm going to look into.
It may be slower as you say, but at least i looked into it. And thanks again, the more and more i look into it, the better it looks.

If you are really wanting to get the fastest boot time that you can, you should look into this:

Welcome to coreboot - coreboot

You should be able even to put a kernel directly on the bios, as long as your motherboard is supported. It has it's risks though. You usually need to hotswap the bios chip while the box is on.

This would eliminate the time required to load the bios firmware and the post tests. You'd be running in linux protected mode from almost the same time you press ON on your computer's case.

[Serpreme]

That sound simply amazing. But it may be a little to complicated. I'll do some research into it.
Thanks for all the links bud, i'm just starting out in the linux world after 12 years of windows, and these few months have been very liberating.
community has been great also.