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Qubes OS architecture documentation

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Architecture. Security-critical code.

Two official Qubes OS documentation pages describing the system’s security-by-compartmentalization architecture and its trusted computing base.

The architecture page explains how Qubes uses the Xen hypervisor to isolate applications into lightweight virtual machines called qubes. Networking and USB stacks run in unprivileged VMs, dom0 has no network code, and the GUI virtualization layer adds roughly 2,500 lines of C to the privileged domain. Templates allow centralized updates across qubes sharing the same base.

The security-critical-code page enumerates the TCB: Xen itself, Xen’s xenstore and block backends in dom0, the RPM signature verification path, and the GUI and qrexec daemons. The project explicitly states that the TCB is on the order of hundreds of thousands of lines of C, several orders of magnitude smaller than mainstream operating systems. Software inside app qubes is trusted from the Fedora Project, signed by Fedora distribution keys.

These pages are primary-source architectural specifications maintained by the Qubes OS team. They describe the design intent and trust boundaries rather than empirical security outcomes.

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