Alpine Linux
Alpine Linux is a community developed operating system designed for routers, firewalls, VPNs, VoIP boxes, containers, 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.
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ZimaOS
ZimaOS is an independently-developed, Linux-based operating system for personal servers and network-attached storage (NAS) devices. It features system-level support for remote access, RAID configuration, over-the-air (OTA) updates, and a browser-based user interface for managing the server.