Hitchhiker's Guide to Openbsd

4.5.3 - Setting up disks
Important Note: Users with a large hard disk (larger than was commonly available when your computer was made) will 
want to see 
this section
 before going any further. 
Laying out your disk appropriately is probably the most difficult part of an OpenBSD install. 
Setting up disks in OpenBSD varies a bit between platforms. For 
i386
, 
amd64
, 
macppc
, 
zaurus
and 
armish
, disk setup is 
done in two stages. First, the OpenBSD slice of the hard disk is defined using fdisk(8), then that slice is subdivided into 
OpenBSD partitions using disklabel(8). 
Some users may be a little confused by the terminology used here. It will appear we are using the word "partition" in two 
different ways. This observation is correct. There are two layers of partitioning in the above OpenBSD platforms, the 
first, one could consider the Operating System partitioning, which is how multiple OSs on one computer mark out their 
own space on the disk, and the second one is how the OpenBSD partition is sub-partitioned into individual filesystems. 
The first layer is visible as a disk partition to DOS, Windows, and any other OS that uses this disk layout system, the 
second layer of partitioning is visible only to OpenBSD and those OSs which can directly read an OpenBSD filesystem. 
OpenBSD's new installer attempts to make your disk layout tasks easier by having a sane default for "general" use. Note 
that many people will still want to customize the default, or use their own disk layout, but new users should probably 
start with this configuration until they see what they need to do differently. Note that the default layout will vary 
depending on how large your disk system is. 
For now, we'll take the defaults on our 40G disk. 
Available disks are: wd0.
Which one is the root disk? (or 'done') [wd0] Enter
Disk: wd0 geometry: 4863/255/63 [78125000 Sectors]
Offset: 0 Signature: 0xAA55
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
-------------------------------------------------------------------------------
0: 06 0 1 1 - 521 254 63 [ 63: 8385867 ] DOS > 32MB
1: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
2: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
3: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
Use (W)hole disk or (E)dit the MBR? [whole] Enter
Setting OpenBSD MBR partition to whole wd0...done.
Note that this disk has a pre-existing partition on it -- using "whole" disk will remove it!. 
Setting up the "whole" disk for OpenBSD does a number of important things: 
●
erases any existing partitions on the disk 
●
creates an MBR and disk signature so the disk can be booted 
●
Creates an OpenBSD partition using the entire disk 
●
Sets that partition as "active". 
http://www.openbsd.org/faq/faq4.html (11 of 43)9/4/2011 10:01:58 AM

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4 - OpenBSD 4.9 Installation Guide
There are many times when you won't want to do that, including: 
●
You wish to retain other OS partitions 
●
You wish to retain "setup", "suspend to disk", or other system partitions 
●
You wish to build a 
multi-booting
system 
Note that it is critical that a new (or never-used for booting) drive has a valid MBR, a valid signature, an OpenBSD 
partition, and a partition flagged as "active". If you don't do these things using the "Use whole disk" option, you need to 
manually make sure they get done. 
More information on fdisk partitioning your disk 
below
. 
Now we will break up our OpenBSD fdisk partition into OpenBSD disk partitions using 
disklabel(8)
: 
Setting OpenBSD MBR partition to whole wd0...done.
The auto-allocated layout for wd0 is:
# size offset fstype [fsize bsize cpg]
a: 1024.0M 63 4.2BSD 2048 16384 1 # /
b: 507.1M 2097215 swap
c: 38147.0M 0 unused
d: 2620.4M 3135791 4.2BSD 2048 16384 1 # /tmp
e: 4143.1M 8502287 4.2BSD 2048 16384 1 # /var
f: 2048.0M 16987323 4.2BSD 2048 16384 1 # /usr
g: 1024.0M 21181627 4.2BSD 2048 16384 1 # /usr/X11R6
h: 3610.7M 23278779 4.2BSD 2048 16384 1 # /usr/local
i: 1961.6M 30673543 4.2BSD 2048 16384 1 # /usr/src
j: 1961.6M 34690971 4.2BSD 2048 16384 1 # /usr/obj
k: 19245.9M 38708399 4.2BSD 2048 16384 1 # /home
Use (A)uto layout, (E)dit auto layout, or create (C)ustom layout? [a] Enter
The installer has presented us with its proposed "Auto layout" for OpenBSD partitions on our disk, which we are going to 
accept. 
If the proposed layout is not appropriate for your needs, you can, of course, edit the default or customize it completely, 
more details on the disklabel partitioning 
below
.