On Fri, 02.04.2010 at 22:20:46 +0200, Henning Brauer <lists-open...@bsws.de> wrote: > * Toni Mueller <openbsd-m...@oeko.net> [2010-04-02 12:25]: > > it would be great to be able to specify a fallback kernel in case > > booting a new kernel fails > how exactly does the bootloader notice your new kernel sitting in ddb?
Good question. I'm not familiar with the boot process, but would assume that the boot loader could set up a timer that triggers an interrupt if not cleared after some time. The interrupt handler, installed by the boot loader, would do something that the boot loader recognizes to select a different kernel at the next reboot. In PCs, there's afaik a mandatory BIOS routine that can be used to issue a warm boot that would preserve some parts of memory. The kernel would clear the timer or diverting the interrupt handler after booting successfully, or if the user asked for entering ddb. -- Kind regards, --Toni++
