[Operator SDK] Use entrypoint of a Docker Image as default Service Command

[Michele Mancioppi]

[Moved to Juju from https://github.com/canonical/pebble/issues/22]

[With Sidecar Charms] Currently if you want to start a container through Pebble you will have to provide the command to start the container in the command field.

This command seems to be equivalent to the ENTRYPOINT field of a Dockerfile, for example.

In the case of a container definition in a Pod in Kubernetes the command field is optional and will default to the entrypoint if none is stated. Similar default behavior in Pebble would make sense. Additionally an arguments field to expand the entrypoint would also be very useful, for further configuration.

More context on how this is done in Kubernetes: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/

Use case of a pod_spec charm where no command option is provided, but a argument option is: https://github.com/charmed-kubernetes/kubernetes-dashboard-operator/blob/main/charms/kubernetes-dashboard/src/charm.py#L79

[Canonical Juju QA Bot (juju-qa-bot)]

This Medium-priority bug has not been updated in 60 days, so we're marking it Low importance. If you believe this is incorrect, please update the importance.

[Harry Pidcock (hpidcock)]

Without introspecting OCI images from within the juju controller, this is not possible. If it is really required, please change back to New.