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Templates

"A template is a master copy of a virtual machine that can be used to create many clones." - VMware ESXi 4 Docs

A template is a very useful way of making many of the same machine without having to build a fresh install from ISO/scratch media. Think of it as a vanilla saved game that can be started from.

A template is nothing more than a VM that has a setting changed in it's config to be marked as a template. This mean that vCenter will treat it differently (unable to start it, the templates only show up in the "VMs and Templates" view, and so forth). In vCenter the admin can convert it easily from template to VM and back. As a template vCenter will allow an admin to pull clone copies of the template. This make a template a "master copy" of a system.

Create a template:
  1. Make sure the VM is off. Otherwise the option will be grayed out.
  2. In the web interface select the VM you wish to use as a template and right-click on it. In the pull-down menu go to "All vCenter Actions" and select "Convert to Template".

  3. If you are in "Hosts and Clusters" view the newly templated machine will disappear as it's not a host or a guest. To view the template and work with it the "VMs and Templates" view must be used.

Deploy from Template:
  1. In "VMs and Templates" view of vCenter right-click on the template to view all of the options for manipulating a template.

  2. Select "Deploy VM from this Template..." to start the deploy wizard. If functions very similarly to the "Create a New VM" wizard. Please see the documentation for that process for more information.

  3. The amount of time a deployment from template to a VM takes is largely dependent on the size of the VM and the speed of the SAN the disk is stored on. Large VMs (25GB+ VMs) can take significant amounts of time.

  4. Once the deployment process is finished a new VM should be ready and waiting for use.
Converting a Template BACK into a VM:
  1. In "VMs and Templates" view of vCenter right-click on the template to view all of the options for manipulating a template.

  2. Select the option "Convert to Virtual Machine" option to start the process. Similarly to the VM creation process a wizard will start asking you what host to put the VM on.

  3. At the end of the wizard click on finish and the template will be turned back into a VM. This allows for updating of the template machine then it can be turned back into a template.