Shell_command has exit code 255 but no error message

Configuration
1

I run HA OS in a qemu virtual guest. frigate lives outside, and I want to access frigate media from HA. Which works so far:

root@xxx:~# cd
root@xxx:~# ssh ha mount -t virtiofs frigate_clips /media/frigate/clips
root@xxx:~# ssh ha df |grep frigate
frigate_clips        11625371040 8258944000 2780466388  75% /media/frigate/clips

Now I need to make this permanent. Changes to /etc/fstab are not permanent. So I defined an automation. It only logs an error 255. What am I doing wrong with the automation?

Workaround would be to just do that ssh command from the host some time after booting HA OS but I really would like to understand what is going on.

logger:
  logs:
    homeassistant.components.shell_command: debug

shell_command:
  mount_frigate_clips: mount -t virtiofs frigate_clips /media/frigate/clips

alias: Frigate Media mounten
description: ""
trigger:
  - platform: homeassistant
    event: start
condition: []
action:
  - service: shell_command.mount_frigate_clips
    data: {}
mode: single
2

Always keep in mind that the SSH addon is not the same environment as HA itself.
Even id your ssh ha mount ... works, it doesn’t mean that HA can access it.

The only SSH that allow you to access the actual OS is:

3

ssh ha docker container list shows containers for homeassistant and addons. Does that not mean ssh ha goes to the HA OS?

My primary question was why I only got error 255 and no error message. Maybe I should have said so more clearly. IMHO, Missing or misleading error message are a bug in itself. They can consume a lot of time and produce lots of frustration when looking for the root cause. For me, improving error messages always has priority over fixing the bug causing the error.

Upon further investigation: stderr created by shell_command only appears in homeassistant.log with loglevel DEBUG. Loglevel ERROR is not sufficient. I think Loglevel ERROR should show stderr.

Am I missing something or should I open an issue?

logger:
  default: info
  logs:
    homeassistant.components.shell_command: debug

2023-12-23 10:45:57.277 DEBUG (MainThread) [homeassistant.components.shell_command] Stderr of command: `mount -t virtiofs frigate_clips /media/frigate/clips`, return code: 255: b'mount: mounting frigate_clips on /media/frigate/clips failed: Resource busy\n'
2023-12-23 10:45:57.277 ERROR (MainThread) [homeassistant.components.shell_command] Error running command: `mount -t virtiofs frigate_clips /media/frigate/clips`, return code: 255