Does Red Hat Enterprise Linux run on Azure?

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Now that Microsoft has moved to General Availability for IaaS on Windows Azure, I decided to spend an hour or two investigating a question which I’ve been asked a couple of times over the last few months. Currently, Microsoft provides a number of Linux ‘platform’ images in the IaaS gallery. These are for OpenLogic CentOS, OpenSUSE and Ubuntu.


CentOS is based on the Red Hat Enterprise Linux distribution, but RHEL, itself, is conspicuous by its absence. This has raised eyebrows over the months, given the widespread use of RHEL in the enterprise, and the desirability to many organisations to run RHEL in the cloud.


I can’t comment on any ‘political’ or commercial reasons why Windows Azure does not currently offer RHEL platform images. Rumours abound as to why there has been no apparent progress towards this. I will simply note that it takes two to tango, and I can’t say if either or both companies are currently blocking this. It would seem strange for either company to play silly games here. RHEL would clearly add to the value proposition of the Azure platform with few, if any, obvious downsides for Redmond. I don’t know what Red Hat’s position is, but again, offering RHEL on subscription to Azure customers would seem, in principle, to be in Red Hat’s interest. RHEL is, of course, only available through paid subscriptions, and while this broadly conforms to the model Microsoft uses for Azure platform images, there may well be issues in reaching a mutually acceptable agreement. This is, of course, pure speculation on my part.


Of course, pre-built, subscription-based platform images are just one way to go. There is no impediment to building your own Linux image or virtual disk and uploading it into Azure. I know of no rule that says you can only use CentOS, OpenSUSE and Ubuntu. Indeed, the Microsoft-run VM Depot currently contains a handful of images that use other Linux distributions (ALT Linux, Debian, Mageia). The question, then, is whether RHEL will run under the Windows Azure hypervisor.


What evidence there is on the Internet suggests that people have been running into problems trying to do this. However, there is a simple technical explanation for this. Although RHEL has, for some time, offered support for Microsoft’s Hyper-V technology, Red Hat has only just, in the last few weeks, released a version that incorporates Microsoft’s Hyper-V Linux drivers. This code was written by Microsoft and contributed to Linux. Indeed, back in 2011, the contribution of this code appears to be a major reason why Microsoft appeared in the top 10 Linux contributors in the Linux Foundation’s annual report.


The incorporation of the Microsoft Hyper-V drivers in RHEL 6.4 suggests that this latest version should work just fine on Windows Azure. Azure uses Hyper-V technology to implement virtualisation, and the Microsoft drivers, I understand, support Windows Azure. Red Hat, however, neglects to mention Windows Azure specifically in their documentation. I could find no evidence on the web of anyone trying to run RHEL 6.4 on Azure.


In such cases, the only thing to do is to try it out. I downloaded the 30-day evaluation copy of RHEL 6.4 and built a VM under Hyper-V on my notebook. I converted the dynamic VHDX file to a fixed-size VHD using Hyper-V Manager. I then uploaded the resulting file to Windows Azure using the Add-Disk option of the CSUpload utility. I created a VM using this disk. I checked that there was a public SSH endpoint and noted the public port. I started PuTTY, entered the host name and port…


…et voilà. It worked. Looks like RHEL 6.4 works just fine on Windows Azure.



Written by Charles Young at 17:00

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