Hitchhiker's Guide to Openbsd

14.9 - Installing Bootblocks - i386/amd64 specific
Modern versions of OpenBSD (3.5 and later) have a very robust boot loader that is much more indifferent to drive 
geometries than the older boot loader was, however, they are sensitive to where the file 
/boot
 resides on the 
disk. If you do something that causes boot(8) to be moved to a new place on the disk (actually, a new inode), you 
will "break" your system, preventing it from booting properly. To fix your boot block so that you can boot 
normally, just put a boot floppy in your drive (or use a bootable CD-ROM) and at the boot prompt, type "b hd0a:/
bsd" to force it to boot from the first hard disk (and not the floppy). Your machine should come up normally. You 
now need to reinstall the first-stage boot loader (
biosboot(8)
) based on the position of the 
/boot
file, using the 
installboot(8)
 program. 
Our example will assume your boot disk is sd0 (but for IDE it would be wd0, etc.): 
# cd /usr/mdec; ./installboot /boot biosboot sd0
If a newer version of bootblocks are required, you will need to compile these yourself. To do so simply: 
# cd /sys/arch/i386/stand/
# make && make install 
# cd /usr/mdec; cp ./boot /boot
# ./installboot /boot biosboot sd0 (or whatever device your hard 
disk is)
14.10 - Preparing for disaster: Backing up and Restoring from tape
Introduction:
If you plan on running what might be called a production server, it is advisable to have some form of backup in 
the event one of your fixed disk drives fails, or the data is otherwise lost. 
This information will assist you in using the standard 
dump(8)
/
restore(8)
utilities provided with OpenBSD. More 
advanced backup utilities, such as "
Amanda
" and "
Bacula
" are available through 
packages
for backing up 
multiple servers to disk and tape.