is there a Helm built-in function that would allow me to write a file within my chart to an external directory?

Question

Our helm charts create the appropriate k8s manifest and they install into our cluster. Associated (or packaged within our helm chart is a rule file which I would like to be able to write to some external directory.

What we would like to do is for an integrator to install an number of our helm charts. Each helm chart they install will have a rule that would be written to some external directory. The integrator after installing all of the associated helm charts would then inspect the rule's directory and then create a configmap containing those rules.

We can't create the configmap until we have install all the helm charts that contribute rules. Is there a helm built in that would allow me to write one (or more) files to an external directory?

Answer 1

No. The only outputs of a Helm chart are Kubernetes resources (that are installed in the cluster) and the plain-text rendered output of the NOTES.txt file.

However, you could install this metadata in the cluster. The easiest way would be to create a ConfigMap with the content you need, and then have the integrator process look for those ConfigMaps and combine them.

kubectl get configmap --all-namespaces -l type=rule -o name

If you want to do this programmatically, you could write a Kubernetes operator that runs in the cluster, and instead of writing out ConfigMaps, write some kind of custom resource; a controller would watch for those resources appearing using the Kubernetes API, and combine them appropriately.