Hitchhiker's Guide to Openbsd

partition the source tree is on will often give significantly better performance. 
5.3.4 - Building the kernel
We will assume you wish to build a standard (GENERIC or GENERIC.MP) kernel here. Normally, this 
is what you want to do. Do not consider building a custom kernel if you have not mastered the standard 
building process. 
Obviously, the kernel is a VERY hardware dependent portion of the system. The source for the kernel is 
in the 
/usr/src/sys
directory. Some parts of the OpenBSD kernel code are used on all platforms, 
others are very specific to one processor or one architecture. If you look in the 
/usr/src/sys/
arch/
directory, you may see some things that look a little confusing -- for example, there are 
mac68k
, 
m68k
and 
mvme68k
directories. In this case, the mvme68k and mac68k systems both use the 
same processor, but the machines they are based on are very different, and thus require a very different 
kernel (there is much more to a computer's design than its processor!). However, parts of the kernel are 
common, those parts are kept in the m68k directory. If you are simply building a kernel, the base 
architecture directories like 
m68k
are not anything for you to worry about, you will be working 
exclusively with the "compound architecture" directories, such as 
mvme68k
. 
Kernels are built based on 
kernel configuration files
, which are located in the 
/usr/src/sys/arch/
<your platform>/conf
 directory. Building the kernel consists of using the 
config(8)
program to 
create and populate a kernel compile directory, which will end up in 
/usr/src/sys/arch/<your 
platform>/compile/<KernelName>
. For this example, we will assume you are using the i386 
platform: 
# cd /usr/src/sys/arch/i386/conf
# config GENERIC
# cd ../compile/GENERIC
# make clean && make depend && make
[...lots of output...]
# make install
Replace "
i386
" in the first line with your platform name. The 
machine(1)
command can tell you what 
your platform name is, so an obvious generalization would be to use the command "
cd /usr/src/
sys/arch/`machine`/conf
" instead on the first line. 
At this point, reboot your machine to activate this new kernel. Note that the new kernel should be 
running before the next step, though if you have followed the 
above
advice about upgrading to the most 
recent available snapshot, it may not matter as much. Sometimes, however, APIs change, and the old 
http://www.openbsd.org/faq/faq5.html (10 of 26)9/4/2011 10:02:02 AM

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5 - Building the System from Source
kernel will be unable to run new applications, but the new kernel will generally support the old ones. 
Note that you can build a kernel without root access, but you must have root to install the kernel.