Since vSphere 2.5, there is a feature allowing you to capture screen shot of a running virtual machine. It’s not well publicized but you can find a short description with screenshotSupported (boolean) in the HostCapability data object. Thanks to Nikita for bringing this up in the comment of the vSphere Java API 2.1 GA post.
Indicates whether the screenshot retrival over https is supported for this host’s virtual machines. If true, a screenshot can be retrieved at the HTTPS relative path /screen?id=<managed object ID of virtual machine or snapshot>. If any of the optional parameters ‘top’, ‘left’, ‘bottom’, and ‘right’ is specified, the returned image will be cropped from the rectangle with upper left corner (left, top) and bottom right corner (right – 1, bottom – 1). These values default to the top, left, bottom and right edges of the image. The client must use an authenticated session with privilege VirtualMachine.Interact.ConsoleInteract on the requested virtual machine or, in the case of a snapshot, the virtual machine associated with that snapshot.
The managed object ID of virtual machine is the value of ManagedObjectReference, which can be easily found using MOB.
Once you have it, you can issue a URL as follows in any browser and get the screen shot in PNG format. Read more »
Author: Steve Jin is the author of VMware VI and vSphere SDK (Prentice Hall), creator of VMware vSphere Java API. For future articles, please subscribe to Email or RSS, and follow on Twitter.
UUID stands for universally unique identifier (UUID). It’s a 128-bit value. vSphere uses it as IDs for many different types of entities like HostSystem, VirtualMachine, Datastore, etc.
The UUID surfaces to the vSphere API as well. You can find many methods use UUID as parameter or return result. The most commonly used one is the SearchIndex.findByUuid() which find you a virtual machine or a host based on its UUID, either instance or BIOS UUID. The format used for UUID is as follows:
52dc2e26-dbc4-7d05-5fed-019d234379d9
Since 4.0, DistributedVirtualSwitchManager managed object is added and it has a method called queryDvsByUuid(). As reported by VI Java API community, the standard format doesn’t work. The accepted format is like this: Read more »
Author: Steve Jin is the author of VMware VI and vSphere SDK (Prentice Hall), creator of VMware vSphere Java API. For future articles, please subscribe to Email or RSS, and follow on Twitter.
What does a promotion mean for a virtual machine’s disks? When you get a promotion, you may have more salary, a better title, bigger office space, etc. For sure a virtual disk cannot earn salary and doesn’t care about title, but it can occupy bigger space in datastore.
In my previous blog, I discussed how to create linked virtual machines using vSphere API. These linked virtual machines share a common disk as base, therefore the total disk consumption is significantly reduced. When a virtual disk is promoted, it gets its own “office” other than sharing it with others.
The vSphere API to promote virtual disks is promoteDisks_Task defined with VirtualMachine type. It has a tricky parameter called “unlink” (type: boolean) . According to the API reference:
1. If the unlink parameter is true, any disk backing which is shared shared by multiple virtual machines is copied so that this virtual machine has its own unshared version. Copied files always end up in the virtual machine’s home directory.
2. Any disk backing which is not shared between multiple virtual machines and is not associated with a snapshot is consolidated with its child backing.
Now when should you use true or false? “If the unlink parameter is true, the net effect of this operation is improved read performance, at the cost of disk space. If the unlink parameter is false the net effect is improved read performance at the cost of inhibiting future sharing.”
Here is the sample code that illustrates the usage of the API: Read more »
Author: Steve Jin is the author of VMware VI and vSphere SDK (Prentice Hall), creator of VMware vSphere Java API. For future articles, please subscribe to Email or RSS, and follow on Twitter.
Application Provisioning
With the right system configuration in place, it’s time to install the applications. So why not use the same tools we used for the OS and middleware? Do we need yet another set of tools?”
It depends. You can use the same set of tools for middleware to install some applications. The middleware appears like an application to the OS as well. The difference is whether your application is stable enough and whether you need to customize per node. The tools like Puppet can be good for stable applications that can be deployed the same way across all nodes. If your application is still a work in progress and you need flexibility to tweak it, you need more specialized application provisioning tools.
The big technical difference between application and middleware provisioning tools is that application tools push the application to the nodes and remotely change anything as needed. The process is procedural.
The middleware provisioning tools normally have agents on the nodes to pull the software based on the prescribed configuration files. The process is declarative.
Beyond the “push” and “pull” difference, the application provisioning tools can also manage the lifecycles of applications (sometimes called services) distributed on different nodes with a single line of command or code. Given the nature of remote command dispatching framework, the application provisioning tool can do almost anything. If there has to be a limitation, it’s your imagination.
So if you develop applications by yourself, you most likely need application provisioning tools.
Let’s see what tools are there. Read more »
Author: Steve Jin is the author of VMware VI and vSphere SDK (Prentice Hall), creator of VMware vSphere Java API. For future articles, please subscribe to Email or RSS, and follow on Twitter.
Cloud computing is an evolutionary technology because it doesn’t change the computing stack at all. It simply distributes the stacks between the service providers and the users. In some sense, it is not as impactful as virtualization technology which introduced a new hypervisor layer in the computing stack and fundamentally changed people’s perception about computing with virtual machines.
But if you look closely at the latest IaaS clouds, they do leverage virtualization as a way to effectively and efficiently deploy systems. Inside one virtual machine, the computing stacks remain the same as before: from OS to middleware to application.
Keep in mind that the application is the end while the OS and middleware are the means. Customers care about applications more than the underlying infrastructure. As long as the infrastructure can support the applications, whatever the infrastructure might be is fine technically. Then the question would shift to the economic side: whatever is the most cost effective wins in infrastructure. That’s why Linux gains more shares in the cloud than in traditional IT shops.
To get to the end, you have to take a mean. In the IaaS cloud, you have to install the underlying OS and middleware before you can run your application. For the PaaS cloud, you can get away from that by focusing on application provisioning.
OS Provisioning
Remember, the software stack inside a virtual machine doesn’t change. It needs OS, middleware and application installed and configured before the application can work. Read more »
Author: Steve Jin is the author of VMware VI and vSphere SDK (Prentice Hall), creator of VMware vSphere Java API. For future articles, please subscribe to Email or RSS, and follow on Twitter.
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