[DavidePrincipi]

When a module update adds an image the module did not have before, update-module stores PREV_<NAME>_IMAGE=None in the module environment, and the cleanup step then runs podman image rm None. The update succeeds, but the log shows a failed removal and the bogus variable stays in the environment. It was found while testing ns8-metrics 1.6.0-dev.1, which adds the metrics-grafana image. NethServer/dev#8210

Updates now record a previous image only when one exists, and remove a stale previous value otherwise. The cleanup step also skips empty and None values, so environments already holding None from earlier releases are handled. Updates that replace an image behave as before.

• update-module/05pullimages: set PREV_<NAME>_IMAGE only if <NAME>_IMAGE was already set, otherwise unset it
• update-module/95cleanup_images: skip previous images that are empty or None; complements fix(update-module): handle missing PREV_IMAGE_URL #1340, which did the same for PREV_IMAGE_URL

How to test

• On a module whose new release adds an image (e.g. metrics 1.5.1 to 1.6.0-dev.1), run update-module and check that no PREV_<NAME>_IMAGE=None is written and the log has no podman image rm None
• On a module environment already holding PREV_<NAME>_IMAGE=None, run an update and check that the value is removed without errors
• Update a module to a release that changes an image and check that the previous image is still removed

These cases were checked on a test node (core 3.23.0 with the two patched steps copied in), including a direct run of 95cleanup_images with None, empty and real previous images.

See also

• fix(update-module): handle missing PREV_IMAGE_URL #1340
• feat: Grafana image with bundled plugins only ns8-metrics#99

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Generated by Claude Code:claude-opus-5.5 with nethserver-pr

[DavidePrincipi]

Tested on a single-node cluster with core 3.23.1-dev.7 (updated from 3.23.1-dev.5), updating metrics1 from 1.5.1 to 1.6.0. In 1.6.0 prometheus and alertmanager change, and metrics-grafana replaces grafana.

Case	Result
Update changes an image	✅ PREV_PROMETHEUS_IMAGE and PREV_ALERTMANAGER_IMAGE are set and the old images are removed
Update adds an image	✅ With METRICS_GRAFANA_IMAGE unset, a forced update to 1.6.0 sets only METRICS_GRAFANA_IMAGE, and a stale PREV_METRICS_GRAFANA_IMAGE is unset
Environment already holds PREV_<NAME>_IMAGE=None	✅ 95cleanup_images skips it: no podman image rm None, no errors

PREV_GRAFANA_IMAGE=None was injected for an image that 1.6.0 no longer lists. 05pullimages does not touch it, so the value stays in the environment. It is harmless because the cleanup step skips it.

The unrelated PREV_IMAGE_URL path logged Error: ghcr.io/nethserver/metrics:1.5.1: image not known, because the module image was not in the module's image storage. The update still succeeded.

All metrics services were running after each update.

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Assisted-by: Claude Code:claude-opus-5-5