Running OpenBSD on Raspberry Pi Zero 2 W

    

I had that Raspberry Pi Zero 2 W lying in a box. And because I changed my network configuration, I decided I could use that Pi as a DNS et DHCP server. But I also wanted to take benefits from my POE switch.

It turns out to be really simple, with the proper hardware. Here are the notes.

Software

Get the OpenBSD installer for ARM. I’m using 7.4.

# ftp https://ftp.openbsd.org/pub/OpenBSD/7.4/arm64/miniroot74.img

Get the Raspberry Pi Zero 2 W Device Tree Blob.

# ftp https://github.com/raspberrypi/firmware/raw/master/boot/bcm2710-rpi-zero-2.dtb

Hardware

I have used:

Attach the Pi to the POE Hat using the provided screws. Plug the HDMI cable to the Pi. Plug the USB keyboard to the Hat.

Do not plug the RJ45 cable, yet.

Installation

Plug the microSDHC to a machine ; I used a ThinkPad running OpenBSD. Transfer the OpenBSD installer onto the card. Add the DTB file to it. Configure OpenBSD to use the HDMI output.

# dd if=miniroot74.img of=/dev/rsd2c bs=1m

# mount /dev/sd2i /mnt/usb
# cp bcm2710-rpi-zero-2.dtb /mnt/usb/
# umount /mnt/usb

# mount /dev/sd2a /mnt/usb
# mkdir -p /mnt/usb/etc
# echo "set tty fb0" >> /mnt/usb/etc/boot.conf
# umount /mnt/usb

Take the microSD card out of the laptop and plug it into the Pi.

Plug the RJ45 cable. The Pi should start and boot from the microSD card.

Thanks to the HDMI monitor and USB keyboard, you can proceed to the OpenBSD installation as usual. Be sure to configure the ure0 network interface as the WiFi card has no available firmware (yet). When asked for disk partitioning, select the “Whole” option. Select an HTTP mirror to install the sets.

When the installation is finished, turn off the Pi, take the microSD card out and plug it back to your other machine. Copy the DTB to the microSD card to be able to boot. Instruct OpenBSD to use the HDMI output.

# mount -t msdos /dev/sd2i /mnt/usb
# cp bcm2710-rpi-zero-2.dtb /mnt/usb/
# umount /mnt/usb

# mount /dev/sd2a /mnt/usb
# echo "set tty fb0" >> /mnt/usb/etc/boot.conf
# umount /mnt/usb

Take the microSD card out and plug it into the Pi. I’m using it headless, with only the RJ45 cable pluggued in. From my testings, the USB switch allows connecting and using USB keyboard and USB sticks (Corsair Flash VoyagetGT 16GB).

The dmesg is available here .

Performance overview

This POE Hat provides a 10/100 Realtek RTL8152 network interface:

# speedtest-cli --simple
Ping: 10.925 ms
Download: 91.35 Mbit/s
Upload: 65.38 Mbit/s

# mount -t mfs -o -s128M /dev/sd0b /mnt
# ftp -o /mnt/test https://cdn.openbsd.org/pub/OpenBSD/7.4/amd64/comp74.tgz
Trying 199.232.171.52...
Requesting https://cdn.openbsd.org/pub/OpenBSD/7.4/amd64/comp74.tgz
100% |*****************************************************| 75644 KB    00:07
77459716 bytes received in 7.74 seconds (9.53 MB/s)
# umount /mnt

Disk performance to download an OpenBSD set:

# ftp -o /root/test https://cdn.openbsd.org/pub/OpenBSD/7.4/amd64/comp74.tgz
Trying 199.232.171.52...
Requesting https://cdn.openbsd.org/pub/OpenBSD/7.4/amd64/comp74.tgz
100% |*****************************************************| 75644 KB    00:15
77459716 bytes received in 15.42 seconds (4.78 MB/s)

Disk performance while installing and extracting the python-3.10.13 package:

      tty                sd0                cpu
 tin tout  KB/t  t/s    MB/s  us ni sy sp in id
   0   92  7.28  303    2.15   7  0  6  1  2 84
   0  326  8.96  350    3.06   6  0  6  0  1 87
   0   49  8.61  262    2.21   5  0  5  1  1 88
   0  132  9.62  422    3.96   4  0  3  1  2 90
   0   50  9.98  363    3.54   3  0  3  0  0 94
   0   49  9.81  357    3.42   2  0  5  1  1 91
   0   90  8.70  454    3.86   3  0  6  1  2 88
   0   48  7.61  411    3.05   3  0  7  1  1 88
   0  128 11.77  450    5.17   8  0  7  0  1 84
   0  126 11.34  370    4.09   7  0  4  2  1 86
   0  159 13.79  323    4.35   7  0  4  0  2 87
   0  120 19.90  158    3.07   6  0  3  2  2 87
   0   49 20.21  126    2.49   3  0  3  1  0 93
   0   84 19.22  151    2.83   1  0  3  0  1 95
   0   80 24.67  124    2.98   3  0 11  5  1 80
   0   81 25.04  282    6.89   7  0  3  0  1 89
   0   79 20.07  292    5.73  13  0 10  3  2 73
   0  107 15.10  279    4.11   4  0  5  1  3 87
   0  106 15.99  314    4.91  10  0 13  7  1 68
   0  129 23.15  345    7.81   6  0  3  2  2 87

Overall responsiveness is quite good.

Now, let’s use it!