Ubuntu Server will be one of the first operating systems offered to customers of VMware's infrastructure-as-a-service (IaaS) cloud, with OS images that should be portable across clouds operated by VMware and rivals such as Amazon.

vCloud Hybrid Service, set to go live in September, will support all 90 or so operating systems certified to run on the vSphere virtualization platform. For most of those, customers will need to install the operating system themselves. A select few will be published by VMware on what's basically an app store, making them a bit more accessible.

VMware's pricing page currently lists just Microsoft Windows Server 2012, Windows Server 2008 R2, and CentOS. It has been reported that SUSE Linux is on its way. Ubuntu will join the party sometime in the fourth quarter, likely November.

"That's certainly what we've been working towards with VMware, that Ubuntu is available on the vCHS [vCloud Hybrid Service] and that it's an Ubuntu image that we produce," Ubuntu Server and Cloud Product Manager Mark Baker told Ars at the VMworld conference this week. "It should be fully compatible and exactly the same as the Ubuntu you'd run on Amazon or [Windows] Azure."

Red Hat Enterprise Linux (RHEL) is a standard option on Amazon, which runs the biggest IaaS cloud, but it's not clear when it might make it onto vCloud Hybrid Service.

VMware and Red Hat are increasingly becoming competitors. With VMware touting its new services and software this week at a conference attended by 22,000 people, Red Hat released a blog post arguing that its "open" approach to hybrid cloud computing is better. Publishing CentOS instead of RHEL could be a snub directed by VMware at Red Hat, as CentOS is essentially a version of Red Hat that customers can get without paying for a Red Hat subscription, compiled from the RHEL source code.

"No comment from us on this one" is the answer a Red Hat spokesperson gave Ars when asked if RHEL will be an option on vCloud Hybrid Service.

UPDATE: VMware has told Ars that it plans to add Red Hat to its catalog of OSes, but did not say when.

vCloud Hybrid Service aims to be a natural extension of VMware's virtualization platform, letting customers run applications in the cloud and in their own data centers and manage them all in the same way.

From a purely technological perspective, ignoring competitive concerns, it would make sense for RHEL to be front and center on the VMware cloud. Red Hat is far and away the most successful enterprise Linux vendor, and VMware is far and away the most successful server virtualization vendor. Although Red Hat would prefer customers to use the KVM hypervisor instead of VMware's, many businesses do run Red Hat's OS on vSphere.

Customers should still be able to use RHEL on the VMware cloud if they install it themselves. VMware has said the cloud "will support the thousands of applications and more than 90 operating systems that are certified to run on vSphere." RHEL is one of those supported operating systems.



Ubuntu users can also upload their own images instead of using the ones provided by VMware and Canonical.

"Customers who created an image on any currently supported version of Ubuntu can transfer that image to the vCloud Hybrid Service," an Ubuntu fact sheet states. "To ensure that VMware provides a safe and secure environment for critical business applications, VMware will only accept images based on versions of Ubuntu for which updates are still being produced."

There wasn't a ton of heavy lifting Canonical had to do to get Ubuntu running on vCHS, Baker said. "A lot of it is validation, testing and making sure it behaves the same way as it does on AWS [Amazon Web Services] or other platforms and that we have a nice model to be able to provide updates," he said.

Baker said Ubuntu 12.04, the Long Term Support release from April 2012, will be on vCloud Hybrid Service, along with more recent versions up through the 13.10 release scheduled for October.

Portability across clouds is a key goal for Canonical. It's inevitable that customers who are heavily dependent on VMware virtualization and management tools would find it complicated to move workloads back and forth between the VMware cloud and the Amazon cloud. But Ubuntu itself won't throw up any roadblocks.

"There's a lot of customer uncertainty about how portable are these things," Baker said. By validating and testing Ubuntu images on Amazon, Azure, and VMware, Canonical hopes to provide some certainty. If you want to move a workload from one cloud to another, "the desired goal is that you don't see any difference at all," he said. Canonical's Juju and cloud-init tools can also help customers deploy workloads to various cloud services.

vCloud Hybrid Service will charge customers by the amount of CPU, RAM, storage, and bandwidth they need. Operating system costs are in addition to that. Windows Server on vCloud Hybrid Service will cost $25 per virtual CPU per month, while CentOS is free.

Ubuntu will be a free download on vCloud Hybrid Service when it's ready in Q4 2013. Customers who pay for the Ubuntu Advantage support service can shift their licenses from on-premises deployments to the VMware cloud.

Canonical and VMware have been ramping up their partnership as of late, collaborating to bring VMware's server and network virtualization technology to OpenStack clouds. Canonical may well be making some cash from VMware, as the company generally charges cloud providers for the right to publish Ubuntu images. VMware will also get "an efficient service for ongoing image maintenance," in Canonical's words.