No documentation on how to set feature flag to disable disk space warning (runner.diskspace.warning/system.runner.lowdiskspacethreshold)

[Peter-McLean-Altera]

Describe the bug
Executing the runner from a docker image with a readonly / small rootfs causes a rather annoying disk space warning.

This warning feature appears to be controlled by very well obfuscated feature flags. I've searched the github runner code, documentation, llm, and google thoroughly and am fairly certain there IS a way to set a lower threshold or completely disable this warning. But, I did not find and documentation on these settings.

To Reproduce
Steps to reproduce the behavior:

1. Launch a github runner on a system with a readonly rootfs with very little free space, but the runner executes from a separate disk with plenty of space (/tmp should also be readable with abundant free space)
2. Run any action
3. You will see the error

"Warning: You are running out of disk space. The runner will stop working when the machine runs out of disk space. Free space left: 15 MB"

4. Search in vain for documentation on setting internal flags such as :

• runner.diskspace.warning
• system.runner.lowdiskspacethreshold

Expected behavior
There should be documented steps to disable this disk space warning or set the threshold to zero.

Runner Version and Platform

Version of your runner? 2.321.0

OS of the machine running the runner? Linux

What's not working?

No method to prevent the disk space warning

Job Log Output

See steps

Runner and Worker's Diagnostic Logs

NA

[indy-singh]

This was a fun little nerd snipe.

Using a self hosted runner on Debian and liberal use of fallocate, left with ~30MB of disk free.

The way to disable the warning is to add a environment variable to the workflow file:-

name: indy-test
run-name: indy-test (${{ github.run_id }})

on:
  workflow_dispatch:

env:
  runner.diskspace.warning: false

jobs:
  import:
    runs-on: 
      group: INDY-TEST    
    steps:
      - name: Say hello
        run: echo "hello world"

Cheers,
Indy

[Peter-McLean-Altera]

Thank you, @indy-singh . I can confirm this removes the warning. I was confused how 'env' vars could have dots '.' in them when AFAIK that is not allowed in Linux. Now I see that the env var has to be specified in the workflow as you demonstrated.

We had tried setting the variable false in a .env file to the runner, and I can even see the runner.diskspace.warning=false in run: env, but the warning only goes away when setting the env var in the workflow file.

It would be nice if these feature flags / env variables were documented so users can discover useful behavior like this.