Kexec

What is kexec?
Kexec lets you reboot faster, skipping hardware initialization by BIOS POST / firmware, and bootloader.

Kexec shutdowns your current kernel, and starts another. It is like a reboot but it is independent of the system firmware. And like a reboot you can start any kernel with it, not just Linux.

What you need

 * kernel >= 2.6.13 with kexec support built-in
 * kernel >= 2.6.13 with kexec support built-in

Kernel configuration
You will need to have kexec support enabled:

Configuring kexec
Configuration is done in. That file is self-documenting. =)

Usage
In Gentoo, Kexec is executed when you reboot, by  command or pressing Ctrl+Alt+Del.

If you want to use kexec once, just run

It'll reserve kexec call at reboot. Later on, you can reboot anytime, letting kexec starts another (or the same) kernel.

If you want kexec to be run every time you reboot, add it to a runlevel:

If you want to reboot the normal way this time, do: