Debug the host

To debug the operating system, you need a shell on the host itself, not inside a container. This page shows the ways in, and where to look once you are there.

Home Assistant OS has an SSH server for developers, Dropbear, on port 22222. It is separate from any SSH app, and only runs when root has at least one authorized key. There is no password login.

1. If you don't have an SSH key yet, create one with ssh-keygen -t ed25519. GitHub's guide to generating a new SSH key covers every operating system.
2. Format a USB drive with the label CONFIG, see the CONFIG USB drive.
3. Create a file named authorized_keys in the root of the drive, without an extension. Put your public key in it, the content of the file ending in .pub, one key per line. Use Unix line endings (LF), and plain ASCII.
4. Plug the drive into the device, and run ha os import, or reboot with the drive plugged in.

Since Supervisor 2026.09.0, the Supervisor API can manage these keys too, with the /os/ssh/authorized_keys endpoints. See the Supervisor API reference in the Apps area.

ssh [email protected] -p 22222

Changed the hostname, or no mDNS on your network? Use the IP address of the device instead.

Import a CONFIG drive without an authorized_keys file. The import removes all keys and stops the SSH server. Through the API, a DELETE on /os/ssh/authorized_keys removes all of root's authorized keys.

On a screen and keyboard, or a virtual machine console, the device shows the Home Assistant CLI, ha >. Type login to get a root shell on the host.

If the CLI does not come up within three minutes, or you press Ctrl+C while it waits, you get an emergency shell instead. That is the way in when the Supervisor does not start.

Many boards also have a serial console. It shows the boot messages, and gives you a login prompt: log in as root, without a password.

The consoles are set in cmdline.txt on the boot partition. The defaults per board:

The kernel writes its messages to every console in cmdline.txt, but the systemd startup messages only go to the one listed last. On every board with a screen, that is console=tty0, so they show on the screen. Home Assistant Yellow has no HDMI port, so it lists its serial console last. To see the startup messages on the serial console of another board, move its console= entry to the end of the line. On boards not in this table, add the serial console yourself, see the board pages.

On boards with GRUB (generic x86-64, generic aarch64, and virtual machines), the boot menu has a rescue shell entry for each slot. It boots the system into systemd's recovery target, with debug output. Useful when the system does not get far enough to start a console.

The journal is stored on the data partition, so it survives reboots. On the host shell:

# The service that starts the Supervisor
journalctl -u haos-supervisor -f

# The Supervisor itself
docker logs -f hassio_supervisor

# Home Assistant Core
docker logs -f homeassistant

# Everything, newest last
journalctl -e

Without host access, the CLI shows most of this too: ha supervisor logs, ha core logs, and ha host logs. Add --help to see the options, like choosing a boot.

Every part of the system is a Docker container. To open a shell in one:

docker ps
docker exec -it homeassistant /bin/bash

The Supervisor overview lists the containers and their names.