Yeah, something strange, really…
I’ve added this extra line to home-assistant.service file to check what shell the Home Assistant is being started:
ExecStartPre=echo $SHELL >> /home/homeassistant/asa.txt
daemon.log showed an interesting result:
Oct 16 08:25:48 localhost systemd[1]: Stopped Home Assistant.
Oct 16 08:27:21 localhost systemd[1]: Reloading.
Oct 16 08:27:37 localhost systemd[1]: Starting Home Assistant...
Oct 16 08:27:37 localhost echo[24133]: /bin/bash >> /home/homeassistant/asa.txt
Oct 16 08:27:37 localhost systemd[1]: Started Home Assistant.
[...]
Oct 16 08:27:55 localhost hass[24134]: /bin/sh: 1: cat: not found
Oct 16 08:27:55 localhost hass[24134]: 2020-10-16 08:27:55 ERROR (SyncWorker_18) [homeassistant.components.command_line] Command failed: cat /sys/class/thermal/thermal_zone0/temp
Now I see that systemd works properly and starts Home Assistant from bash. But then, Home Assistant (for unknown reason) fires its own command line scripts from (much limited) sh shell. Gosh, why?
Or more precisely, why this happen only when HA is autostarted by this systemd script?