No log file generated

Hi, I’m just hand on with Drone.io.
First of all, Thanks developers for this very great tools.

I’m setting up “runner exec” on Mac following the document steps.
https://docs.drone.io/runner/exec/installation/macos/

However, I server was up and running.
I was able to open the dashboard in the browser
but there is no log file at all.

DRONE_RPC_PROTO=http
DRONE_RPC_HOST=localhost
DRONE_RPC_SECRET=xxxx
DRONE_LOG_FILE=.drone-runner-exec/log.txt
DRONE_LOGS_DEBUG=true
DRONE_LOGS_TEXT=true
DRONE_LOGS_PRETTY=true
DRONE_LOGS_COLOR=true
DRONE_UI_USERNAME=root
DRONE_UI_PASSWORD=root

What I’m done wrong here?

I noticed some of the runner variables in the above configuration, related to logging, are invalid. For more information about configuring logging and the appropriate variables:
https://docs.drone.io/runner/exec/configuration/logging/

and for a reference of runner configuration parameters:
https://docs.drone.io/runner/exec/configuration/reference/