AppVMs

AppVMs are a type of virtual machine used in Qubes OS to run individual applications in isolated security compartments. An AppVM is created from a Template VM, which provides the base operating system and software; the AppVM receives a writable private storage layer while sharing the template's read-only filesystem. This separation allows applications to run in separate processes and desktops while minimizing the risk that a compromise in one AppVM will affect others or the base system. AppVMs are connected to a NetVM for all external network access; network traffic is controlled by the NetVM's firewall rules.

Administration and lifecycle: Administrators can configure each AppVM with a specific template, memory and CPU quotas, and networking policies. When the template is updated, existing AppVMs may require a restart or rebuild to incorporate updates. AppVMs can be shut down and restarted without affecting others. For dangerous tasks, disposable VMs (DisposableVMs) can be used; these are ephemeral and automatically discarded after use.

Isolation and data sharing: Communication between AppVMs is restricted by policy; clipboard and file transfer between VMs can be allowed or blocked per policy. Private storage areas prevent cross-VM leakage of changes or data. Users can assign different AppVMs to different applications or workflows (for example, a web browser in one AppVM, a document editor in another).

Limitations and considerations: The architecture introduces performance overhead and requires careful security management. Users must be aware of template updates and data transfer across VMs. AppVMs are a central feature of the defense-in-depth strategy in Qubes OS but are not a one-size-fits-all solution.