Currently, kubeadm would refuse to perfom an upgrade (or even planing for one)
if it detects a user supplied unsupported component config version. Hence,
users are required to manually upgrade their component configs and store them
in the config maps prior to executing `kubeadm upgrade plan` or
`kubeadm upgrade apply`.
This change introduces the ability to use the `--config` option of the
`kubeadm upgrade plan` and `kubeadm upgrade apply` commands to supply a YAML
file containing component configs to be used in place of the existing ones in
the cluster upon upgrade.
The old behavior where `--config` is used to reconfigure a cluster is still
supported. kubeadm automatically detects which behavior to use based on the
presence (or absense) of kubeadm config types (API group
`kubeadm.kubernetes.io`).
Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>
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