Discussion
I'm kinda obsessed with serial (UART) CLI interaction with Linux hosts lately.
To access a Raspberry Pi 4 running Home Assistant OS:
Mount the first partition on its SD card. Add
dtoverlay=uart2
to the [pi4] section in config.txt there, and
console=ttyAMA2,115200
to the kernel command line in cmdline.txt.
Then, connect 3v3 UART on GPIO0 (Pi's TX) and GPIO1 (Pi's RX), Ground on Pin 25 or 30 (see https://pinout.xyz/pinout/uart), and reboot.
Login: root, no password.
Pro tip: When connected to a Linux host via a serial connection, you can run
eval `resize`
on many hosts to have them query your terminal for its current size, and propagate that to the running applications.
You'll need to re-run that every time you change the terminal size, because there's no SIGWINCH-like mechanism over serial links.
If you use #systemd ≥ 257, it does that for you on login:
https://github.com/systemd/systemd/pull/33707
But only once; size changes afterwards still don't propagate.
![Terminal screenshot. I'm running the command: tio /dev/ttyUSB1
Output:
[15:07:51.571] tio 3.9
[15:07:51.571] Press ctrl-t q to quit
[15:07:51.642] Connected to /dev/ttyUSB1
homeassistant login: root
Welcome to Home Assistant OS.
Use `ha` to access the Home Assistant CLI.
# [cursor]](https://assets.chaos.social/media_attachments/files/117/524/588/844/816/683/original/4c79b1c3a74cf017.png)
Note that on a Raspberry Pi 5, things are different, I haven't researched any of that.
The Pi 4 usually has its Bluetooth adapter running on UART0, and UART1 is a limited "mini UART", which is why we need to move the serial console over to UART2.
See https://www.raspberrypi.com/documentation/computers/configuration.html#uarts for the technical details.
https://contributors.home-assistant.io/os/operating-system/raspberry-pi/#serial-console also has instructions by the HAOS team, but they unnecessarily disable Bluetooth instead of just using UART2.
#HomeAssistant
Raspberry Pi