Comment 7 for bug 2055288

> The relations should be done automatically by the charm.
> But once it's running on error, this step is also not done.

No, that's not how it works. A subordinate charm needs to be "deployed" (essentially, added to the model), and then related (integrated in newer-speak) to the principle charm (in this case manila) for it to be added to the principle's unit. Deploying a subordinate charm doesn't add it to any units.

> deployer@ic-infra1:~$ juju add-relation manila manila-generic
> ERROR ambiguous relation: "manila manila-generic" could refer to "manila-generic:juju-info manila:juju-info"; "manila:manila-plugin manila-generic:manila-plugin"; "manila:remote-manila-plugin manila-generic:manila-plugin"

This just means that you need to do (after the manila-generic charm is deployed):

    juju add-relation manila:manila-plugin manila-generic:manila-plugin

That will resolve the correct relation and then add the manila-generic subordinate unit to (all of) the manila unit(s).

Note this, though from the manila-generic readme:

> This charm exists to provide an example backend for Manila, for the purpose of test and reference. It is NOT intended for production use in any case.

Please be sure that this is the subordinate charm that you wish to use. If it's for testing it is fine, but otherwise, it's not a production charm. Thanks.