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through VM templates within vCenter Server. We'll show you how templates work in the next
section.
Creating Templates and Deploying Virtual Machines
In a vSphere environment, what would traditionally take several hours to do is now reduced to
a matter of minutes. In this chapter, you've already seen how you can quickly and easily spin
up new VMs with VM cloning and customization specii cations, complete with the guest OS
already installed. The templates feature of vCenter Server builds on this functionality to help
you roll out new VMs quickly and easily with limited administrative effort while protecting the
master VMs from inadvertent changes.
You'll Need vCenter Server for This Feature
Because templates leverage cloning to deploy new VMs, it's possible to use templates only when
you are using vCenter Server to manage your ESXi hosts.
vCenter Server offers two different options for creating templates: Clone To Template and
Convert To Template. In both cases, you'll start with a VM that already has an instance of a
guest OS installed. As the name suggests, the Clone To Template feature copies this initial VM
to a template format, leaving the original VM intact. Similarly, the Convert To Template feature
takes the initial VM and changes it to template format, thereby removing the ability to perform
power operations on the VM without converting back to VM format. Using either approach,
once the VM is in template format, that template cannot be powered on or have its settings
edited. It's now in a protected format that prevents administrators from inadvertently or unin-
tentionally modifying the “gold image” from which other VMs are deployed.
When considering which VMs you should convert to templates, remember that the idea
behind a template is to have a pristine system coni guration that can be customized as needed
for deployment to the target environment. Any information stored on a VM that becomes a tem-
plate will become part of the new system that is deployed from that template. If you have VMs
that are critical servers for production environments that have applications installed, those are
not good candidates for becoming templates. The best VMs to use for templates are VMs that
have a new, clean installation of the guest OS and any other base components.
In fact, we recommend creating a new VM specii cally for use as a template or creating the
template from a VM as soon after creation as possible. This ensures that the template is as pris-
tine as possible and that all VMs cloned from that template will start out the same way.
You can convert a VM to a template using the context menu of the VM or the Convert
To Template link in the Commands list. Figure 10.9 shows two ways an existing VM can be
changed into a template format. Because templates cannot be modii ed, to make changes or per-
form updates to a template you must i rst convert the template back to a VM, then update it, and
 
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