This mini guide explain how to update an OpenBSD server with no CD reader. You still need to access the server during boot to change the boot kernel.
4.x folder directly under root as this is default during installation.bsd.rd kernel.Roughly this means running the following commands.
scp -r /Volumes/OpenBSD4.4/4.4 root@192.168.0.104:/
ssh root@192.168.0.4
reboot
boot wd0a:/4.4/i386/bsd.rd (at boot prompt)
export PKG_PATH=ftp://ftp.sunet.se/pub/OpenBSD/4.4/packages/i386
pkg_add -ui -F update -F updatedepends
See 4.5 Upgrade FAQ for an examle of how configuration files may be upgraded. In some cases the system will work perfectly without any changes in configuration.
To do remote upgrade requires that you are connected to the server via a serial port console. This enables you to reboot the machine and access the boot promt after reboot. Several guides exists where this setup is explained. There are also special builds of OpenBSD which enables remote update via SSH e.g. Yaifo.
See Bootable Installation From USB Flash Sticks for a more thorough description.