ref: ff5d6e119f3b6d1a6e7e7752db5de3adab6386ad
dir: /rpi-p9.ms/
Plan 9 Installation for Raspberry Pi Zero WH
First, download Richard Miller's Plan 9 image:
https://9p.io/sources/contrib/miller/9pi.img.gz
gunzip the file to get 9pi.img, then use dd to copy this image onto a microSD card.
Next, we need to configure config.txt and cmdline.txt to specify the proper boot
settings. For reference, see
https://www.raspberrypi.com/documentation/computers/config_txt.html.
Mount the microSD card and make a few edits.
In cmdline.txt, add the definition console='0 b115200' to the end of the line.
NOTE: everything must be on a single command line. Multiple lines will not be parsed
correctly in cmdline.txt.
In config.txt, the block for the pi zero (or the [all] block) should include the lines:
enable_uart=1
core_freq=250
You will need a USB to TTL serial cable (see https://www.adafruit.com/product/954).
It must be attached to the correct pins (see https://learn.adafruit.com/raspberry-pi-zero-creation/give-it-life)
Afterwards, if the machine to which the USB cable is connected is running Linux,
you might run a command such as:
$ sudo screen /dev/ttyUSB0 115200
Afterwards, you should see output like the following:
time...
fossil(#S/sdM0/fossil)...version...
init: starting /bin/rc