Getting OpenBSD 6.2 installed on my Thinkpad T420s was surprisingly easy. This was the first time I installed OpenBSD on bare metal, so I had a lot of wonderful discoveries this evening.
All in all, OpenBSD was a joy to use. Old school, really Unixy, no
bloat. Just edit text files and issue commands. Nothing more. No
magic. No systemd, no NetworkManager, no PulseAudio. After
installing the OS, which was a pure text based, simple question and
answer style installer (you know, the kind of BASH scripts you made
second year in Uni), it said:

Man, I instantly fell in love in OpenBSD ♥
A quick reboot later, X came up with a login screen looking awfully
lot like xdm:

Network configuration
Really old school. Back to basics. So nice, so simple. Minimal conf:
See all the network devices the kernel has recognised with ifconfig,
then create a file:
/etc/hostname.<device>
Wireless
After connecting my laptop to a wired connection, I installed missing firmware for the Intel wireless card with:
# fw_update -a
Suspend & resume
Suspend to RAM and resume worked flawlessly without doing much. I just
had to start apmd:
# apmd &
To make apmd start on the next boot, as well as make it scale the
CPUs up and down, I added the following to /etc/rc/.conf.local:
apmd_flags=-A
I could then suspend to RAM as a regular user by typing (I started apmd;
$ zzz
and hibernate (suspend to disk) by typing the same in upper case letters:
$ ZZZ
Issues
Slow booting
I'm hit by this error: OpenBSD 3.1 slow boot due to pciide error - Ars Technica OpenForum. Luckily suspend and resume works flawlessly so I "never" need to do a cold boot.
Useful reading
Apart from the man pages, I found the following articles helpful:
- OpenBSD FAQ: Networking
- Installing OpenBSD 6.1 on your laptop is really hard
(not)
- An OpenBSD
Workstation
- List installed packages on Linux or FreeBSD / OpenBSD system
nixCraft