Is it possible to "return" to GRUB after booting Linux without restarting

I am dual-booting Windows and Linux on my SSD and find myself often switching between the two OSes. The SSD is really fast and both OSes boot in about 3 seconds once selected in GRUB. However, it takes forever (about 30 seconds) for my BIOS, RAID and second SATA controller to initialize before I'm finally in GRUB.

So I was wondering if it is possible to skip these initializations and just "return" to GRUB once I have booted Linux. Ideally I would also be able to do the same from within Windows but my hope is not very high there :)

I did a little search online and found nothing but a somewhat out-dated linux loader - loadlin.exe, which one could run from within Dos or Windows 95/98 to boot Linux. So at least the concept of switching OSes without rebooting is not new. Anyone know of a current tool that does this?

If not, is there a technical issue that prevents us from writing such a program or is there simply not enough demand?

UPDATE: A friend of mine just told me about Kexec. Using that it seems to be possible to start a different Linux kernel from within a running kernel, but is it possible to go back to GRUB or start a windows installation directly?

Solution 1:

Using kexec you can solve the problem. There is no need to involve GRUB. You can use kexec-loader to boot directly into different operating systems from within Linux. (Make sure kexec support is compiled into your kernel.)

Solution 2:

Check if you have UEFI support. That can DRASTICALLY improve booting speed.

Solution 3:

Long story short, not with the way things work now. A better approach may be to find why your BIOS/RAID/SATA controller is taking so long. There might be BIOS updates available, and possibly firmware updates for the raid controller.

Solution 4:

No. Unless your BIOS has a specific setup option to skip POST during a reboot (I saw it once) this hasn't existed since Windows 98/ME (the Fast Reboot trick which really only reloaded Windows.)

Maybe someone with enough time boot hacking could reproduce that and reload GRUB, but it would have to change how INIT restarts the system.