Qubes OS
Qubes OS is a free and open-source, security-oriented operating system for single-user desktop computing. Qubes OS leverages Xen-based virtualization to allow for the creation and management of isolated compartments called qubes.
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MiniOS
MiniOS is a Debian-based Linux distribution which strives to be lightweight, modular, versatile and customisable. It comes in three editions, "Standard", "Toolbox" and "Ultra".