ImageOS environment variable changed without warning

[mhanberg]

Type of issue

• Error when running a workflow.
• Request for additional tools or software for an existing image.
• Request for a new image, Linux or Windows.
• Other

Describe the issue

We use the ARM Linux Ubuntu 24 partner image as part of our CI, as well as the erlef/setup-beam action.

The setup-beam action utilizes the ImageOS environment variable, which on earlier releases of these partner images, mimicked the behavior of the GitHub official images, in being something like ubuntu24 or ubuntu22.

Today, our CI started failing because this variable is now set to "Linux", which breaks the setup-beam workflow.

To Reproduce

Run a job with that workflow on an ARM Linux runner.

Expected behavior

The ImageOS variable is appropriately set.

Note

Our workaround is the manually set this environment variable, which is setup-beam's suggestion when using self-hosted runners.