Hitchhiker's Guide to Openbsd

9 - Migrating to OpenBSD
Table of Contents
●
9.1 - Tips for users of other Unix-like Operating Systems
 
●
9.2 - Dual boot of Linux and OpenBSD
●
9.3 - Converting your Linux (or other Sixth Edition-style) password file to BSD-style.
●
9.4 - Running Linux binaries on OpenBSD
●
9.5 - Accessing your Linux files from OpenBSD
For more information for Linux users, please refer to 
http://sites.inka.de/mips/unix/bsdlinux.html
. 
9.1 - Tips for users of other Unix-like Operating Systems
While OpenBSD is a very traditional Unix-like operating system and will be very familiar to those who 
have used other Unix-like systems, there are important differences. New users to OpenBSD must look at 
their own experience: if your only knowledge of Unix is some experience with one variant of Linux, you 
may find OpenBSD "strange". Rest assured, Linux looks pretty strange to anyone who starts from 
OpenBSD. You must recognize the difference between "standard" and your experience. 
If you learned Unix from any of the 
good books
on general Unix, understanding the "Unix philosophy" 
and then extended your knowledge to a particular platform, you will find OpenBSD to be a very "true" 
and familiar Unix. If you learned Unix using a "type this to do that" process or a book such as "Learn 
PinkBeenie v8.3 in 31.4 Hours", and told yourself you "know Unix", you will most likely find 
OpenBSD very different. 
One important difference between OpenBSD and many other operating systems is the documentation. 
OpenBSD developers take great pride in the system 
man pages
. The man pages are the authoritative 
source of OpenBSD documentation -- not this FAQ, not third-party independently maintained pages, not 
"HOWTO"s, etc. When a developer makes a change to the system, they are expected to update the man 
pages along with their change to the system code, not "later" or "when they get around to it" or "when 
http://www.openbsd.org/faq/faq9.html (1 of 5)9/4/2011 10:02:12 AM

---

9 - Migrating to OpenBSD
someone complains". A manual page exists for virtually every program, utility, driver, configuration 
file, and so on on the stock system. It is expected that a user will check the man pages before asking for 
help on the 
mail lists
. 
Here are some of the commonly encountered differences between OpenBSD and other Unix variants. 
●
OpenBSD is a fairly pure "BSD-Style" Unix, following the 4.4BSD design closely. Linux and 
SCO Unix are "System V" style systems. Some Unix-like operating systems (including some 
Linux distributions) mix many SysV and BSD characteristics. A common place where this causes 
confusion is the 
startup scripts
, OpenBSD uses the traditional BSD4.4-style 
rc(8)
style. 
●
OpenBSD is a complete system, intended to be kept in sync. It is not a "Kernel plus utilities" that 
can be upgraded separately from each other. Failure to keep your system (kernel, user utilities, 
and applications) in sync will result in bad things happening. 
●
As many applications are not developed to directly compile and run on an OpenBSD 
environment, OpenBSD has a 
ports tree
, a system where users can easily acquire code, patch it 
for OpenBSD, install dependencies, compile it, install and remove it in a standardized and 
maintainable way. Pre-compiled 
packages
 are created and distributed by the OpenBSD ports 
team. Users are 
encouraged
to use these packages over compiling their own. 
●
OpenBSD uses CVS to keep track of source code changes. OpenBSD pioneered 
anonymous 
CVS
, which allows anyone to extract the full source tree for any version of OpenBSD (from 2.0 
to current, and all revisions of all files in between) at any time, and you can access the most 
recent changes within hours of its commit. There is also a very convenient and easy to use 
web 
interface to CVS
. 
●
OpenBSD produces an official release available on 
CD
 and 
FTP
 every six months on a 
predefined schedule
. Snapshots for all supported platforms are made semi-regularly with the 
current development code. It is the goal that the source tree is kept fully buildable and the 
resultant system usable at all times. The tree is occasionally broken, but this is an extraordinary 
event that will be corrected rapidly, not something that will be permitted to continue. 
●
OpenBSD contains 
strong cryptography
, which can not be included with OSs based in some 
countries. 
●
OpenBSD has gone through heavy and continual security auditing to ensure the quality (and thus, 
security) of the code. 
●
OpenBSD's kernel is 
/bsd
. 
●
The names of hard disks are usually 
/dev/wd
(IDE) and 
/dev/sd
(SCSI or devices emulating 
SCSI disks). 
●
/sbin/route
 with no arguments in Linux gives the state of all the active routes, under OpenBSD 
(and many other OSs), you need the "show" parameter, or do a "
netstat -r
". 
●
OpenBSD does NOT support Journaling Filesystems like ReiserFS, IBM's JFS or SGI's XFS. 
Instead we use the 
Soft Updates
 feature of the already very robust Unix Fast File System (FFS) to 
accomplish the goals of performance and stability. 
●
OpenBSD comes with 
Packet Filter (PF)
, not ipfw, ipchains, netfilter, iptables, or ipf. This means 
http://www.openbsd.org/faq/faq9.html (2 of 5)9/4/2011 10:02:12 AM

---

9 - Migrating to OpenBSD
that Network Address Translation (known as IP-Masquerading in Linux), queuing, and filtering 
is done through 
pfctl(8)
, 
pf(4)
, and 
pf.conf(5)
. See the 
PF User's Guide
 for detailed configuration 
information. 
●
Interface address is stored in 
/etc/hostname.
(for example, 
/etc/hostname.
dc0
 for a NIC using the 
dc(4)
 driver). It can contain a hostname (resolved in 
/etc/hosts
) instead 
of an IP address. 
●
The machine name is in 
/etc/myname
. 
●
The default gateway is in 
/etc/mygate
. 
●
OpenBSD's default shell is 
/bin/ksh
, which is 
pdksh
, the Public Domain Korn shell. Other 
included shells are 
csh
 and 
sh
. Shells such as bash and tcsh can be added as 
packages
 or installed 
from 
ports
. Users familiar with bash are encouraged to 
try ksh(1)
 before loading bash on their 
system -- it does what most people desire of bash. 
●
Password management on OpenBSD is different from password management on some other 
Unix-like operating systems. The actual passwords are stored in the file 
master.passwd(5)
which 
is readable only by root. This file should be altered only with the 
vipw
 program. 
●
Devices are named by driver, not by type. For example, there are no eth* devices. It would be 
ne0 for an NE2000 Ethernet card, and xl0 for a 3Com Etherlink XL or a Fast Etherlink XL 
Ethernet device, etc. All of these drivers have man pages in section 4. So, to find more 
information about the messages your 3c905 driver is putting out, you can do "
man 4 xl
". 
●
OpenBSD/i386, amd64, and several other platforms use a "two layer" disk partitioning system, 
where the first layer is the 
fdisk
, BIOS-visible partition, familiar to most users of IBM 
compatible computers. The second layer is the 
disklabel
, a traditional BSD partitioning system. 
OpenBSD supports up to 15 disklabel partitions on a disk, all residing within one fdisk partition. 
This permits OpenBSD to coexist with other OSs, including other Unix-like OSs. OpenBSD must 
be one of the four "primary" partitions. 
●
Some other OSs encourage you to customize your kernel for your machine. OpenBSD users are 
encouraged
 to simply use the standard GENERIC kernel provided and tested by the developers. 
Users attempting to "customize" or "optimize" their kernel usually cause far more problems than 
they solve, and will not be supported by developers. 
●
OpenBSD works hard to maintain the 
license policy
and 
security
of the project. For this reason, 
some newer versions of some software which fail to meet either the license or security goals of 
the project have not and may never be integrated into OpenBSD. Security and free licensing will 
never take a back seat to having the biggest version number.