Sensor platform command_line "command failed"

Configuration
1

New guy here. I think I’m getting the general hang of it all, but I’ve run into a problem with trying to read a sensor output using

sensor:
   - platform: command_line

I’m setup as (from System Health):

  • Host OS is raspbian buster
  • dev=false
  • docker=true
  • hassio=true
  • installation_type=Home Assistant Supervised
  • version 0.112.4
  • virtualenv=false

I may eventually come back here for specific syntactical help, but before that, I have three general questions:

  1. I’ve found the logger capability and set it up in configuration.yaml (variously debug and notset to get as much info as possible). I’ve also found home-assistant.log. Are there other logs anyplace else I should be looking at? All I get from home-assistant.log is ERROR…Command failed".
  2. When running a command under command_line, what is the context I’m in? Is it the underlying (rasbian) OS context? Is it the busybox context I see when I use Terminal & SSH add-on? Other? If I manually run a command in that context, am I guaranteed it will work in the command_line command?
  3. What are the debugging tools available to me for troubleshooting command_line issues?

Thanks in advance for teaching me to fish…

-Mark