When attempting to run "dkp upgrade kommander" using a charts bundle for airgap environments, you may encounter an error that resembles the following:
uploading chartbundle from "dkp-kommander-charts-bundle-v2.X.X.tar.gz" to chartmuseum
chartmuseum returned status 400 Bad Request, body: {"error":"gzip: invalid header"}
Ensuring helm-mirror implementation is migrated to chartmuseum
failed to ensure "helm-mirror implementation is migrated to chartmuseum": could not install chartmuseum: unable to upload charts from bundle dkp-kommander-charts-bundle-v2.3.1.tar.gz: unable to upload chart from chartbundle to chartmuseum, NOTICES.txt, dkp-kommander-charts-bundle-v2.3.1.tar.gz: unexpected reply from chart museum: 400 Bad Request
This error indicates that the dkp binary ran into a problem when trying to extract a nested tar.gz file.
The "dkp-kommander-charts-bundle-v2.X.X.tar.gz" file has another "dkp-kommander-charts-bundle-v2.X.X.tar.gz" file inside it, along with a "NOTICES.txt" file that is required for third party licensing.
To resolve this error, first extract the file with "tar -xzvf", then retry "dkp upgrade kommander", this time referencing the new "dkp-kommander-charts-bundle-v2.X.X.tar.gz" file that was inside it.