not-os is a minimal, embedded-focused Linux distribution built entirely as a Nixpkgs overlay, demonstrating how to construct a bootable OS from scratch (kernel, initrd, squashfs root) using NixOS modules while replacing systemd with runit. The repository provides configurations for x86_64 QEMU, Raspberry Pi (ARM), and Xilinx Zynq targets, along with an iPXE boot chain featuring cryptographic signature verification for secure boot. It illustrates advanced Nix techniques for building custom initrds, integrating firmware, and creating reproducible embedded system images, though some components (like the dummy stage-2 init script placeholder) indicate a focus on flexibility over polish. The codebase is well-structured with clear module boundaries and includes Hydra CI integration for automatic testing.
phusion/baseimage-docker is a specialized Ubuntu base image optimized for Docker containers. It solves common Docker container problems including the PID 1 zombie reaping issue (via a custom /sbin/my_init process), syslog blackhole problem (using syslog-ng that forwards logs to docker logs), and APT incompatibilities. The image provides service supervision through runit, tools for running processes as different users (setuser), easy SSH access (optional), and environment variable management. It's designed to be used as a base image for Docker applications, offering a minimal but production-ready Ubuntu environment.