The following should work:
juju set-model-constraints root-disk-source="encrypted-ebs"
For all other storage you want to probably set this as well:
juju model-config storage-default-block-source="encrypted-ebs"
The following should work:
juju set-model- constraints root-disk- source= "encrypted- ebs"
For all other storage you want to probably set this as well:
juju model-config storage- default- block-source= "encrypted- ebs"