Raspberry Pi

Home Assistant OS supports the Raspberry Pi 3, 4, and 5, all 64-bit. Home Assistant Yellow is built on the same board support, with a Compute Module 4 or 5.

Board	Build target	Bootloader
Raspberry Pi 3 Model B and B+	rpi3_64	U-Boot
Raspberry Pi 4 Model B	rpi4_64	U-Boot
Raspberry Pi 5	rpi5_64	Firmware tryboot
Home Assistant Yellow	yellow	U-Boot

All of them use the Raspberry Pi Linux kernel, not mainline. The board files are in buildroot-external/board/raspberrypi/.

On Raspberry Pi 3 and 4, the Raspberry Pi firmware loads U-Boot (kernel=u-boot.bin in config.txt), and U-Boot picks the slot. Raspberry Pi 5 boots without U-Boot: the firmware loads the kernel of the active slot directly, and an update uses the firmware's tryboot mechanism to test the new slot. Always reboot a Raspberry Pi 5 with systemctl reboot after a manual update, see the update system.

config.txt and cmdline.txt are on the boot partition. Changes to them survive OS updates.

On Raspberry Pi 3 and 4, the serial console is not enabled by default. To enable it on the GPIO header (pin 6 is ground, pin 8 is TX, pin 10 is RX):

1. Add enable_uart=1 and dtoverlay=disable-bt to config.txt. The overlay moves Bluetooth off the main UART.
2. Add console=ttyAMA0,115200 to cmdline.txt.

Home Assistant Yellow has its serial console enabled, on ttyAMA2 at 115200 baud.

1. Add dtparam=i2c_arm=on to config.txt.
2. Load the i2c-dev module at boot: a file with the line i2c-dev in the modules/ folder of a CONFIG USB drive, or in /etc/modules-load.d/ on the host.

Raspberry Pi 4 and 5 can boot from a USB drive, if their bootloader in EEPROM is recent enough. Home Assistant OS includes the EEPROM tools. ha os boards raspberrypi firmware update updates the bootloader from the CLI.

Some things to know:

• Remove every bootable SD card. The firmware tries the SD card first.
• Booting is slower, because the firmware looks at the SD card before USB.
• Not every USB to SATA adapter works. On Raspberry Pi 4, cmdline.txt already contains usb-storage.quirks for adapters known to need them. The Raspberry Pi 5 image has none. If yours misbehaves, find its USB ID and add a quirk for it.
• Without an SD card, add dtparam=sd_poll_once=on to config.txt, to stop the kernel from polling the empty slot.

Raspberry Pi 3 Model B can boot from USB after program_usb_boot_mode=1 is set once in config.txt. That change is permanent: it is written to one-time programmable memory.

Bluetooth is on by default. If you don't need it, dtoverlay=disable-bt in config.txt turns it off.