LinuxKit is a toolkit for building custom, minimal, immutable Linux distributions designed to run as container-based virtual machine images. The system is primarily a Go-based CLI tool (`linuxkit`) that reads declarative YAML configurations specifying a kernel, init system, onboot containers, and long-running services. It orchestrates the assembly of these components into bootable output formats (kernel+initrd, ISO, qcow2, VHD, raw disk, etc.) using Docker/BuildKit for package building and containerd/runc as the base runtime inside the target OS. The repository also contains extensive kernel build infrastructure with support for multiple kernel series (4.x, 5.x, 6.x), including real-time (PREEMPT_RT) patches, and cloud platform integration for running images on AWS, GCP, Azure, Equinix Metal, Hyper-V, VMware, QEMU, and macOS Virtualization Framework. While the core tool is well-structured and features reusable patterns like an OCI image cache and a generic package builder, the overall codebase shows signs of maintenance slowdown (last major release v0.8 in 2020, some deprecated kernel series, and experimental projects that may be stale). It remains a solid, professionally built system for immutable OS assembly with a strong emphasis on security and reproducibility.