How does OpenBSD/i386 boot?
The boot process for OpenBSD/i386 is not trivial, and understanding how it works can be useful to troubleshoot a problem when things don’t work. There are four key pieces to the boot process: • Master Boot Record (MBR): The Master Boot Record is the first physical sector (512 bytes) on the disk. It contains the primary partition table and a small program to load the Partition Boot Record (PBR). Note that in some environments, the term “MBR” is used to refer to only the code portion of this first block on the disk, rather than the whole first block (including the partition table). It is critical to understand the meaning of “initialize the MBR” — in the terminology of OpenBSD, it would involve rewriting the entire MBR sector, not just the code, as it might on some systems. You will rarely want to do this. Instead, use fdisk(8)’s “-u” command line option (“fdisk -u wd0”). While OpenBSD includes an MBR, you are not obliged to use it, as virtually any MBR can boot OpenBSD. The MBR is mani
