Hitchhiker's Guide to Openbsd

Setting active partitions
This is probably the most overlooked, and yet, sometimes the best solution for multibooting. Simply set the active 
partition in whatever OS you are currently using to be the one you want to boot by default when you next boot. Virtually 
every OS offers a program to do this; OpenBSD's is 
fdisk(8)
, similar named programs are in Windows 9x and DOS, and 
many other operating systems. This can be highly desirable for OSs or systems which take a long time to shut down and 
reboot -- you can set it and start the reboot process, then walk away, grab a cup of coffee, and come back to the system 
booted the way you want it -- no waiting for the Magic Moment to select the next OS. 
Boot floppy
If you have a system that is used to boot OpenBSD infrequently (or don't wish other users of the computer to note 
anything has changed), consider using a boot floppy. Simply use one of the 
standard OpenBSD install floppies
, and 
create an 
/etc/boot.conf
file (yes, you will also have to create an 
/etc
directory on the floppy) with the contents: 
boot hd0a:/bsd
to cause the system to boot from hard drive 0, OpenBSD partition 'a', kernel file 
/bsd
. Note you can also boot from 
other drives with a line like: "
boot hd2a:/bsd
" to boot off the third hard drive on your system. To boot from 
OpenBSD, slip your floppy in, reboot. To boot from the other OS, eject the floppy, reboot. (You can, of course, use this 
floppy to make a bootable CD, too.) 
http://www.openbsd.org/faq/faq4.html (32 of 43)9/4/2011 10:01:58 AM

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4 - OpenBSD 4.9 Installation Guide
The 
boot(8)
program is loaded from the floppy, looks for and reads 
/etc/boot.conf
. The "
boot hd0a:/bsd
" 
line instructs boot(8) where to load the kernel from -- in this case, the first HD the BIOS sees. Keep in mind, only a small 
file (
/boot
) is loaded from the floppy -- the system loads the entire kernel off the hard disk, so this only adds about five 
seconds to the boot process.