The first step is to determine if the target system meets the minimum installation requirements. A list of supported platforms can be found here. Most recent platforms are supported. Other ones have been dropped for various reasons. This tutorial is for the X86_64, or amd64, platform only and may or may not be applicable to other platforms.
The minimum amount of available space is only 512MB but requires more advanced knowledge and goes beyond the scope of this tutorial. The minimum amount of recommended space is 8GB which should allow for a simple installation.
Consider creating a backup of the system before attempting to install OpenBSD. Especially in case of an intended multiboot system since a mistake in drive number or partition is quickly made. The backup should not be stored on the system that’s the target of the installation but instead on another system like a NAS or NFS share, or on an external hard drive or USB stick.
Schrodinger’s backup: The condition of any backup is unknown until a restore is attempted.
The OpenBSD installer will ask you multiple questions during the installation. Although the default answers provided by the installer are normally usable, it’s good to look into the following in anvance.
If the target machine is connected to a network with a DHCP server, the networking information should be provided automatically. If there’s no DHCP server available, you need the following information:
The OpenBSD installer uses a ramdisk kernel named bsd.rd which creates the environment needed to install OpenBSD but also provides tools that can be useful in a disaster recovery scenario.
The kernel can be booted in multiple ways.
Once the kernel is booted, the installer asks the first question.
... root on rd0a swap on rd0b dump on rd0b erase ^?, werase ^W, kill ^U, intr ^C, status ^T Welcome to the OpenBSD/amd64 X.X installation program. (I)nstall, (U)pgrade, (A)utoinstall or (S)hell?
Choose (I)nstall and follow the instructions.
One of the questions is about which filesets you want to install. The OpenBSD distribution is broken up into multiple parts called sets. Depending on the intended purpose of the machine, as well as the available space, you can either install all sets or only the required ones. Installing all sets is recommended for new users.
The following file sets are available:
In case you realize later that a previously not installed set is needed after all. You can boot the bsd.rd kernel by rerunning the installer and instead of (I)nstall choose (U)pgrade. Move through the installer but select the filesets you need when asked about them.
Unlike some other operating systems, OpenBSD encourages users to split their disk into a number of partitions, rather than just one or two large ones. Some of the reasons for doing so are: OpenBSD recommends users to split their disk into multiple partitions. Rather than the simple layout in for example most Linux distributions like:
The reason OpenBSD encourages users to do so is threefold:
The installer is able to create the partitions automatically based on the available space. This might not be what you want but does provide a good starting point for modifications and should be fine for new OpenBSD users.
At the end of the installation, the installer asks if you’d like to send information about the machine to the OpenBSD developers. Doing this is completely voluntary but helps the developers understand the type of platforms the software is used on and whether or not there are hardware support issues that should be resolved by modifying or adding drivers.
If you choose not to during the installation, you can still send the information later via:
$ (dmesg; sysctl hw.sensors) | mail -s "Some information about the machine" firstname.lastname@example.org