TemplateVMs

TemplateVMs are a core concept in the Qubes OS operating system. They function as read-only, unchangeable virtual machines that serve as blueprints for creating other virtual machines, known as AppVMs. When you install a new operating system, such as a Linux distribution, in Qubes OS, you do so within a TemplateVM. This TemplateVM is then used as the source for any number of AppVMs.

The primary advantage of this architecture is security and efficiency. Because TemplateVMs are read-only, they cannot be compromised by malware or accidental changes made within an AppVM. If a virus infects an AppVM, it can only affect that specific AppVM and cannot spread to the TemplateVM or other AppVMs derived from it. To update or modify the operating system, you only need to update the TemplateVM. All AppVMs based on that template will automatically inherit the changes upon their next startup.

This approach significantly reduces resource usage. Instead of installing and maintaining separate copies of an operating system for each application or task, multiple AppVMs share the same underlying TemplateVM. This saves disk space and memory. When creating an AppVM, it essentially links to the TemplateVM, only storing its own unique changes and user data separately. This makes the system more manageable and less prone to errors.