Due to the way the file system is organized into the disk, it is not possible to patch the disk on the parent without invalidating (thus destroying all modifications made since then).

The recommended procedure to update a template would be:

1. Create a new Virtual Machine from a template
2. Install updates and make any other changes you wish
3. Save & Commit the VM
4. Move the updated VHD file to the template folder (with another name different from the current template)
5. Update the <Template> entry with the information
• Change the ID of the template
• Add the same path
• Keep the same <Name> & <Description>
6. Mark the original template as disabled

After that any new VM created will use the new template. You can use the report on the Administration section to monitor when the old template is idle

• Delete the original template when it is idle