For Google Cloud Platform, the answer to that second question now seems to be yes. Last month, Google joined the OpenStack Foundation, with the goal of making sure that Linux containers and Google-backed Kubernetes container cluster management will work well in OpenStack environments.

Since OpenStack is seen as the leading brand for private cloud, that gives Google (GOOG) a potentially better story in the hybrid cloud arena where customers keep some workloads and data behind their own firewalls, while utilizing shared public cloud infrastructure for other jobs, or to handle spikes in their workloads.

Joe Sandoval, director of cloud platforms at Lithium, said Kubernetes, which the company deployed with help from OpenStack provider Mirantis, could be a game-changer in allowing companies to move workloads from cloud to cloud. “At the highest level, I have one goal: I wanted cloud portability without sacrificing developer productivity,” he told Fortune recently. Support for Kubernetes is crucial there, he said.

Google also inked a pact with VMware, the virtualization kingpin in company data centers, that will enable VMware(VMW)vCloud Air public cloud customers to more easily use Google services like BigQuery and Google Cloud Storage. That would give Google cloud a potential toe hold inside corporate shops.

Up until last year, public cloud leader Amazon’s answer to almost any question seemed to be that it welcomed the flow of customer data and applications into the Amazon (AMZN) Web Services cloud and was working hard to facilitate that with products like Storage Gateway, as well as IT-friendly tools that let VMware or Windows System Center administrators manage AWS resources as well.

But last year, AWS chief Andy Jassy signaled a pretty dramatic shift in Amazon’s seemingly all-public-cloud-all-the-time worldview, acknowledging that some customer computing jobs would not necessarily move to public cloud.

Competitors like to point out that Amazon continues to tout public cloud for more and more corporate workloads—completely understandable since AWS is (by far) the largest public cloud around. But they also maintain that AWS still lacks the sort of ties to private clouds that will make companies with mission-critical data and applications that they want to control more comfortable with cloud computing in general.

“AWS today is like Windows of yesteryear. It’s really popular, everyone uses it, but it’s a black box,” said the executive in charge of the cloud computing effort at one AWS rivals but who would not speak on the record because he doesn’t like “to disparage” competitors. At least on the record.

Companies like Microsoft(MSFT), IBM(IBM), and Cisco(CSCO), all of which have pre-existing ties to customer IT shops, clearly want to push the private cloud-hybrid cloud-public cloud mix of options: It’s only natural that they would paint AWS as a public-cloud-only option.

“Look, AWS is the largest public cloud out there but it’s also the only hold-out that does not have a private cloud strategy,” said Scott Sanchez, director of Cisco cloud strategy.

A more independent observer, Gartner analyst Lydia Leong, said both Amazon and Google “see cloud-first (and eventually nearly cloud-only) as the primary goal.”

But, both companies also know they need to ease that transition to cloud, she added. AWS has been doing it with things like the aforementioned VMware vCenter and Microsoft System Center adminstration tools. AWS, which launched in 2006, has critical mass. It is the de facto cloud for most startups and is used by a growing number of bigger companies as well. Google, on the other hand, with its roots in Internet search and advertising, is relatively new to this cloud business.

“Google right now also needs to generate demand for Google Cloud Platform services, and I think they see the containers/Docker/Kubernetes trend as a way of trying to shift the conversation, playing into themes of portability and the like,” Leong said.

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