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What is VMware VM Customization Specification

VMware vCenter server has many built in features & functionalities which makes your life easy to deploy, manage & maintain your private datacenters. This is one of the very useful feature in vCenter server which is VM Customization specification which we will discuss today.

In Simple words VM Customization Specification is a policy which allows you to simply deploy the pre-configured virtual servers with removing of some manual tasks & human errors. When you deploy any VM you can select the VM Customization Specification policy which you have created to apply for that VM. It works on windows servers as well as on Linux servers but you must first check the guest OS compatibility.

VM Customization Specification allows you to deploy the VMs in the standard way where each VM will have the proper identification, configuration , networking etc. So it will also help you to make your VM deployment process more simpler.

So which all things which can be achieved using VM Customization Specification policy:

VM Registration information :

You can set the VM registration information to the virtual servers such as server owner name & owner organization. Which helps you to easily identify the details of your virtual servers.

Computer name:

You can set your virtual servers name using different ways available such as Use the virtual machine name, Enter name in Clone/Deploy wizard, Enter name & Generate a name using the custom application configured with vCenter Server. So using this options you can either provide the name at the time of deployment of the VM, You can set the predefined names & add the numeric values to the VM names & more.

Windows License:

Using this feature you can provide the license for your windows server where after deployment of windows VMs, It will be licensed. This feature only works with the windows servers.

Administrator Password:

You can configure & set the administrator password for your windows servers directly using this policy. So you don’t need to manually set & configure passwords on each servers.

Time Zone:

You can directly configure the Time zones for your VMs here in the policy. So you don’t need to set the time zones inside the each VMs again.

Commands to run once:

You can specify commands to run the first time a user logs in to the guest operating system. This is based on your own requirements where if you want to run any commands when the guest os starts. You can see the Microsoft Sysprep documentation for information about RunOnce commands.


You can configure networking for your guest operating systems directly from the policy. There are 2 options to configure here first you can use the standard network settings for the servers which uses DHCP on all the network interfaces. Second manually which allows you to set the network configuration directly using specific DHCP server or you will get prompt while deploying the VMs.

Workgroup or domain:

Every server which is part of datacenter belongs to some or the other domains. So you can directly set the workgroup of the guest os here or you can directly join the guest os into the domain by providing credentials who has the permission.

Above mentioned all the things can be configured in the VM Customization specification but may differ on the windows & Linux servers. Most of the things will work on the windows servers.

If you have already created any customization specification file then you can easily import your customization specification as well. For import you must have at least one customization specification saved as an xml file located on a file system accessible from the vSphere Client.

For using VM Customization specification you must configure the virtual machine and guest to meet VMware Tools and virtual disk requirements. Other requirements apply, depending on the guest operating system type.

Below are some of the mandatory requirements:

VMware Tools : The latest version of VMware Tools must be installed on the virtual machine or template to customize the guest operating system during cloning or deployment.

Virtual Disk requirements: The guest operating system being customized must be installed on a disk attached as SCSI node 0:0 in the virtual machine configuration.

Guest OS requirements: Customization of Windows guest operating systems requires the virtual machine to be running on an ESXi host running version 3.5 or later. Customization of Linux guest operating systems requires that Perl is installed in the Linux guest operating system.

In the next post we will see on how we can create VM customization specification policy step by step.

That’s it for Today Friends. I Hope you liked reading this post & If you find anything more to be added or removed feel free to write it in our comments. If you find it useful You are Feel free to share this on social media to help others & spread knowledge.
If you have any query on any thing you are free to write it in our comments section & we will make sure to provide you the better solution as soon as possible.

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VMware Customization Specification

Mayur Parmar

Hi I am Mayur Parmar. Independent Author & Founder of Mastering VMware. I am working in IT industry for more than 4 Years with knowledge of VMware , Microsoft Server's, Linux Server's.

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