Hitchhiker's Guide to Openbsd

Windows NT/2000/XP NTLDR
To multiboot OpenBSD and Windows NT/2000/XP, you can use NTLDR, the boot loader that NT uses. To multi-boot 
with NT, you need a copy of your OpenBSD Partition Boot Record (PBR). After running installboot, you can copy it to a 
file using 
dd(1)
, following a process similar to: 
# dd if=/dev/rsd0a of=openbsd.pbr bs=512 count=1
Note: this is a really good time to remind you that blindly typing commands in you don't understand is a really bad idea. 
This line will not work directly on most computers. It is left to the reader to adapt it to their machine. 
Now boot NT and put 
openbsd.pbr
in C:. Add a line like this to the end of 
C:\BOOT.INI
: 
c:\openbsd.pbr="OpenBSD"
When you reboot, you should be able to select OpenBSD from the NT loader menu. There is much more information 
available about NTLDR at the 
NTLDR Hacking Guide
. 
On Windows XP you can also edit the boot information using the GUI; see the 
XP Boot.ini HOWTO
. 
Programs that do much of this for you are available, for example, 
BootPart
. This program can be run from Windows 
NT/2000/XP, and will fetch the OpenBSD PBR, place it on your NT/2000/XP partition, and will add it to 
C:\BOOT.
INI
. 
Note: The Windows NT/2000/XP boot loader is only capable of booting OSs from the primary hard drive. You can not 
use it to load OpenBSD from the second drive on a system. 
Windows Vista
With Vista, Microsoft dropped NTLDR support in favor of their newer Boot Configuration Data (BCD) store used for 
controlling the boot environment. Since 
BOOT.INI
is no longer available for customization, a command-line utility, 
bcdedit
, takes its place. 
Once OpenBSD's PBR is copied to Vista's system partition, the following three commands are required to select and boot 
OpenBSD when the system is restarted: 
C:\Windows\system32> bcdedit /create /d "OpenBSD/i386 4.9" /application 
bootsector
The entry {05a763ce-d81b-11db-b3ec-000000000000} was successfully 
created.
C:\Windows\System32>
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4 - OpenBSD 4.9 Installation Guide
The GUID returned here, 
05a763ce-d81b-11db-b3ec-000000000000
, is shown for illustrative reasons. Take 
note of the GUID displayed when you run this command as this value will need to be copied into the following 
commands. Simply copying the GUID shown above will not work. 
The following two commands are also required: 
C:\Windows\system32> bcdedit /set {05a763ce-d81b-11db-b3ec-
000000000000} device boot
The operation completed successfully.
C:\Windows\system32> bcdedit /set {05a763ce-d81b-11db-b3ec-
000000000000} path \openbsd.pbr
The operation completed successfully.
C:\Windows\system32>
This must be run in a shell with administrative privileges. Once you've located cmd.exe, right click to be able to select 
"run as administrator". 
Note the absolute pathname of the imported PBR file. Do not add a drive letter as it is assumed that the file is placed in 
the system partition. 
bcdedit
will not complain about an explicit drive specification, but the boot manager will later 
balk claiming that it cannot resolve the designated pathname. 
Upon rebooting, Vista will be listed first in the boot manager ultimately followed by OpenBSD. Selecting either entry 
will boot the corresponding operating system. 
If nothing happens, look around in the control panel for boot information. Most likely, your Windows boot is set up with 
no delay, so you don't see the boot menu. You can also use this to boot OpenBSD by default. 
For more information, consult 
bcdedit
's help by issuing: 
C:\Windows\system32> bcdedit /?
or by searching Microsoft's documentation and Website. A good introduction can be found in this TechNet 
Frequently 
Asked Questions
 article. 
For those who find manual configuration daunting, 
EasyBCD
 provides a GUI alternative.