Add Environment Variable Override

[trankin]

I need to be able to manage settings on this service via Environment Variables. I've added the ability to override anything in the settings schema with a corresponding environment variable.

e.g. to override settings.serial.port you can set ZIGBEE2MQTT_SERIAL_PORT=/dev/ttyS0
to override the mqtt username you can set ZIGBEE2MQTT_MQTT_USER=testusername

This new addition will not perform any action on existing installations unless the matching environment variable is set. I have tested this setting string, number, boolean, object and array values.

[trankin]

I see this is failing for code coverage... I'm working on adding a test that will complete this.

[Koenkk]

Could you explain the use case for this?

[trankin]

Could you explain the use case for this?

Sure, basically it's because I'm using a fleet manager to deploy and manage applications on hosts. I can set up configurations for all of the computers to share settings in the fleet manager via environment variables and it performs the work of syncing those settings down to the devices. It's much easier for me to deploy changes across the entire fleet via environment variables rather than managing the configuration.yaml on a per device basis.

[Koenkk]

Thanks, wrote some docs here: https://github.com/Koenkk/zigbee2mqtt.io/blob/develop/docs/information/configuration.md#override-via-environment-variables

[qm3ster]

Can the overrides mutate configuration.yaml?
@trankin what do you do to manage coordinator_backup.json and devices.yaml(or corresponding section of configuration.yaml) in your fleet?

[trankin]

@qm3ster the overrides to not mutate configuration.yaml. My addition of the env variable feature simply overrides settings after the configuration.yaml file has been loaded. In my set up devices.yaml and/or coordinator_backup.json would still be stored locally to the device.