I doubt the parent really cares about whether or not it's a root volume, but for the record you can mount it to root.

It'll just essentially be empty, which means you have to add a step of populating root with something useful. You'd have to either try and use an initContainer to copy in a filesystem at runtime, have ceph give you a pre-populated directory, probably via thin provisioning, or do something out of band (I've did this in k8s).

This is usually more effort than it's worth though, as container runtimes populate the root for you with whatever you want anyway. Plus, if you start treating containers as blobs like VMs, you'll end up in the situation where you don't know where your important variable data is, which leads to situations where people forget to back it up and test it.

I only said "root volumes" as it's a common use case for EBS volumes. For instance with etcd running in a container you would want the host volume to be an EBS volume since it's critical it's a critical K8S component.

Right, but you would only need to mount the etcd data partition (/var/lib/etcd afaik), rather than the entire node and/or container.

The main problem you have here, is chicken and egg. How do you use a StorageClass, kubernetes PVC, or rook to provision Block Storage for etcd, when you need etcd for kubernetes to function, and you need kubernetes to function for rook, et all.

At some point, you need to bootstrap the world, which is people either start off with cloud APIs, ansible, or PXE.

."The main problem you have here, is chicken and egg. How do you use a StorageClass, kubernetes PVC, or rook to provision Block Storage for etcd, when you need etcd for kubernetes to function, and you need kubernetes to function for rook, et all."

I totally agree. The EBS lifecycle management is generally handled by something like Terraform. That's why I was wondering if the use case for Rook is primarily bare-metal Kubernetes since AWS/GCP et al. already provide these. So I'm wondering that even in a bare-metal environment where you still need to use config management tools like Ansible/Terraform to do things like provision block storage what's the upside of Rook over existing iscsi/Ceph/minio installations?