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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OmegaLinux
OmegaLinux is an Arch-based, rolling-release Linux distribution featuring the lightweight LXDE desktop. It is suitable for installation on older computers with as little as 1 GB of memory.