Alpine Linux is a community developed operating system designed for x86 routers, firewalls, VPNs, VoIP boxes and servers. It was designed with security in mind; it has proactive security features like PaX and SSP that prevent security holes in the software to be exploited. The C library used is uClibc and the base tools are all in BusyBox. Those are normally found in embedded systems and are smaller than the tools found in GNU/Linux systems.
Alpine Linux Xen
Xen Dom0 LiveCD and Xen packages.