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Building your own Virtual Appliances using OVF properties Part 2

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In the previous article, we reviewed the concepts and basic approach to building your own VMware Virtual Appliance (OVF/OVA). In Part 2, we are now going to take a look at a reference implementation for building a Linux VA using VMware PhotonOS. Although I am using PhotonOS as the guest, you can apply these same techniques to any other Linux distribution of your choice.

Step 1 - Create a new VM in vCenter Server and then install PhotonOS using the ISO format. Once you have completed the OS installation, you may want to apply any patches or packages that you want included as part of your VA. Once that is done, go ahead and shut down the VM.

Step 2 - Select the VM in the vSphere Inventory and then click on Configure->vApp and then check the Enable vApp Options. Once enabled, select OVF environment for the IP allocation scheme. In the OVF Details tab, select VMware Tools for the OVF environment transport. (Optionally) You can specify some additional metadata including appliance name and URLs to help others who maybe consuming your VA once it has been exported to an OVF/OVA.

Step 3 - Next, add the following 6 OVF properties which will be used as input to configure networking within PhotonOS. Click Add and provide a Label, Key and optional Category.

Label Key Category
Hostname guestinfo.hostname Networking
IP Address guestinfo.ipaddress Networking
Netmask guestinfo.netmask Networking
Gateway guestinfo.gateway Networking
DNS Server guestinfo.dns Networking
DNS Domain guestinfo.domain Networking


Step 4 - Power back on the VM and once it is available on the network (assuming DHCP), download and copy the sample first boot script rc.local to /etc/rc.d/rc.local. This script is where all the magic happens and will process the OVF property input and then configure the network settings. Right now it assumes these fields are optional, meaning if they left blank, it will default the system to DHCP. If you provide all input properties, then it will go ahead and configure a static network address.

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Building your own Virtual Appliances using OVF properties Part 1

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This has been a topic I have been wanting to write about for quite some time, especially as I get asked about this on fairly regular basis from both partners and customers. I normally point folks over to our official Virtual Appliance (VA) authoring tool, VMware Studio which includes a number of development resources to help get started. Studio is used by many of our partners when creating their VA offerings, although it may not be the easiest thing to get started with, it does provide a complete end-to-end solution.

Most recently, I found myself building out a couple of VAs for my own day to day use, including a custom PhotonOS OVA that allows me to configure a static network address during deployment through the use of custom OVF properties. The official PhotonOS OVA that VMware ships does not provide this option and automatically defaults to DHCP. If you want to setup a static IP Address, you would need to first deploy the VM and then login to the console or SSH (if you have DHCP enabled) and then manually update the networking settings.


For my use case, Studio was going to be overkill and not to mention it may not even support PhotonOS or other modern OSes in general. However, everything that is needed to build your own VA is actually available right in vCenter Server. This was the perfect opportunity and excuse for me to finally document *my* process, in case it can help others wanting to do the same, especially for a home lab setup. In Part 1, I will take you through the two important concepts of building your own VA and then in Part 2 and Part 3, we will take a look at building both a Linux and Windows VA. I will also publish a reference Linux and Windows implementation so that you can use that as a basis to build your own VA, which is not limited to just Linux or Windows, it can be ANY GuestOS that vSphere supports.

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Hidden OVF 2.0 capablity found in the vSphere Content Library

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There are a number of new and useful capabilities that have been introduced in the OVF 2.0 specification. One such capability which I thought was really interesting and that could easily benefit VMware-based solutions is the ScaleOutSection feature. This feature allows you specify the number of instances of a given Virtual Appliance to instantiate at deployment time by making use of pre-defined OVF Deployment Options which can also be overriden by a user.

Lets use an example to see how this actually works. Say you have a single Virtual Appliance (VA) and the application within the appliance can scale to N, where N is any number greater or equal to 1. If you wanted to deploy 3 instances of this VA, you would have to deploy it 3 separate times by either by running through an OVF upload or deploying it from a template. In either case, you are performing N-instantiations. Would it not be cool if you could still start with a single VA image and specify at deployment time the number of instances you want to deploy and only need to upload the VA just once? Well, that is exactly what the OVF ScaleOutSection feature provides.

Below is a diagram to help illustrate this feature further. We start out with our single VA, which contains several pre-defined Deployment Options which can contain any text you wish for the logical grouping. In this example, I am using the terms "Single", "Minimal" and "Typical" to map to number of VA's to deploy which are 1, 3, and 4 respectively. If we choose the "Minimal" Deployment option, we would then get 3 instantiated VA's. If we decide that the defaults are not sufficient, we could also override the default by specifying a different number which the VA supports.

OVF20_ScaleOut
A really cool use case that I had thought about when I first came across the ScaleOutSection feature was to make use of it with my Nested ESXi Virtual Appliance. This capability would make it even easier to standup a vSphere or VSAN Cluster of any size for development or testing purposes. Today, vSphere and many of the other VMware products only support OVF 1.x specification and as far as I know, OVF 2.0 was not something that was being looked at.

Right before holiday break, I was chatting with one of the Engineers in the Content Library team and one of the topics that I had discussed in passing was OVF 2.0 support. It turns out that, although vSphere itself does not support OVF 2.0, the vSphere Content Library feature actually contains a very basic implementation of OVF 2.0 and though not complete, it does have some support for the ScaleOutSection feature.

This of course got me thinking and with the help of the Engineer, I was able to build a prototype version of my Nested ESXi Virtual Appliance supporting the ScaleOutSection feature. Below is a quick video that demonstrates how this feature would work using a current release of vSphere 6.0. Pretty cool if you ask me!? 🙂

Demo of Prototype Nested ESXi Virtual Appliance using OVF 2.0 ScaleOut from lamw on Vimeo.

Now, before you get too excited. There were a couple of caveats that I found while going through the deployment workflow. During the deployment, the VMDKs were not properly being processed and when you power on the VMs, it was as if they were empty disks. This was a known issue and I have been told this has already been resolved in a future update. The other bigger issue is how OVF properties are handled with multiple instances of the VA. Since this is not a supported workflow, the OVF wizard is only brought up once regardless of the number of instances being deployed. This means that all VAs will inherit the same OVF values since are you are only prompted once. The workaround was to deploy the VAs, then go into each individual VA and update their OVF properties before powering on the VMs. Since OVF 2.0 and the ScaleOutSection feature is not an officially supported feature, the user experience is not as ideal as one would expect.

I personally think there are some pretty interesting use cases that could be enabled by OVF 2.0 and ScaleOutSection feature. A few VMware specific solutions that I can think of off the top of my head that could potentially leverage this capability are vRealize Log Insight, vRealize Operations Manager and vRealize Automation Center to just name a few. I am sure there are others including 3rd party and custom Virtual Appliances that have been developed and I am curious to hear if this is something that might be of interest to you? If you have any feedback, feel free to leave a comment and I can share this with the Content Library PM.