Comment 5 for bug 1871940

actions (to date) are intended to run on the workload, to do things like initiate backups or whatever. For k8s charms, juju copies the charm code and hook commands to the workload pod under /var/lib/juju so this can happen. You can absolutely exec into the workload pod and call juju-run.

If the workload docker image does not have Python or other dependencies installed out of the box, it's up to the charm to provide something like an init container combined with a shared mount point to pull in the required dependencies.

BTW, for the new (experimental) charms acting as k8s operators, actions do run in the charm pod since the charm itself is the workload.