On Sun, 8 Nov 2015 11:52:48 +0100 Stefan Sperling <s...@stsp.name> wrote: > On Sat, Nov 07, 2015 at 07:57:05PM -0500, Jonathan Thornburg wrote: >> At this point the machine can boot and run sd1[aeg] fine. *But* if I >> enter "boot sr1d:/bsd" at the "boot>" prompt, the machine boots sd1[aeg], >> not the desired sd1[dfh]. In other words, at this point my "backup" >> sd1[dfh] partitions aren't usefully bootable :(. > > You cannot boot a kernel from a non-'a' partition. > The bootloader won't look elsewhere.
As far as I know The boot loader itself should be located on 'a' partition at least on i386 or amd64 BIOS boot loader, but kernel seems to be able to be booted from non-'a' parition partition. This actually works at least on hd?? on amd64. When starting the kernel, the boot loaders pass the 'bootdev' parameter to the kernel. Below is the definition of 'bootdev' in sys/reboot.h. /* * Constants for converting boot-style device number to type, * adaptor (uba, mba, etc), unit number and partition number. * Type (== major device number) is in the low byte * for backward compatibility. Except for that of the "magic * number", each mask applies to the shifted value. * Format: * (4) (4) (4) (4) (8) (8) * -------------------------------- * |MA | AD| CT| UN| PART | TYPE | * -------------------------------- */ it includes the parition number. So booting from non-'a' partition seems to be intended. --yasuoka
