iPXE is an open-source network boot firmware that provides a full PXE implementation with enhanced capabilities. It operates as a pre-boot environment, replacing or supplementing traditional BIOS/UEFI PXE ROMs. The firmware supports booting over HTTP/HTTPS, iSCSI, Fibre Channel over Ethernet (FCoE), AoE, InfiniBand, and wireless networks, with full TLS 1.2 support including modern cipher suites (ECDHE, GCM, X25519, P-256/P-384). It includes a built-in command-line shell, scripting engine, interactive menus, and extensive hardware drivers for network cards, USB controllers, and storage devices across x86, ARM, RISC-V, LoongArch, and s390x architectures. The architecture is modular and table-driven: drivers, protocols, commands, and startup functions are registered via compile-time tables (e.g., `__pci_driver`, `__net_protocol`, `__command`), enabling a highly configurable build. The core uses an interface/refcount pattern for object-oriented-like composition, with reference-counted objects and asynchronous data transfer via `struct interface`. The codebase is well-structured with clear separation between architecture-specific code (under `src/arch/`), platform interfaces (EFI, BIOS, Linux userspace, SBI), and generic core logic. A comprehensive test suite (over 50 unit tests plus Wycheproof vectors) validates cryptographic primitives, network protocols, and data structures. Key entry points include `src/core/main.c` (generic boot flow), EFI application entry (`efiprefix.c`), BIOS PXE ROM entry, and Linux userspace binary. The firmware is typically embedded into option ROMs, UEFI drivers, or bootable images. External dependencies are minimal—the firmware runs directly on hardware or under a hypervisor, relying only on platform firmware services (UEFI, BIOS, SBI) for low-level operations.
mkosi is a command-line tool for building customized, bootable OS images. It wraps distribution package managers (dnf, apt, pacman, zypper, apk) and deeply integrates with systemd components (systemd-nspawn, systemd-repart, systemd-boot, systemd-vmspawn, ukify) to produce disk images, containers, unified kernel images, initrds, and extension images. The tool supports multiple output formats (disk, tar, cpio, uki, esp, sysext, confext, portable, oci, directory, addon) and can generate images for a wide range of Linux distributions including Fedora, Debian, Ubuntu, Arch, CentOS, openSUSE, and more. The architecture is a modular Python application with a central build pipeline orchestrated in mkosi/__init__.py. Configuration is handled via layered INI-style files with conditional [Match]/[Assert] sections, allowing complex multi-image builds. A sandbox abstraction (sandbox.py) isolates tool execution using Linux namespaces, mounts, and seccomp filters. Distribution-specific installers are registered via a class registry pattern in mkosi/distribution/__init__.py. The tool also provides standalone subcommands: mkosi-initrd, mkosi-addon, mkosi-sandbox, each with its own entry point. Key features include incremental caching, SecureBoot signing, verity and TPM support, kernel-install integration, tools tree for reproducible builds, and a comprehensive manifest generation. The codebase is well-structured with clear separation between configuration, sandboxing, package management, and image creation. It has extensive tests (pytest with integration markers) and active CI.
Rufus is a Windows-native GUI application for creating bootable USB drives and formatting removable media. In production it is a single binary that drives raw disk I/O through Win32/NT APIs, parses ISO/WIM/VHD/FFU images, decompresses archives in many formats, formats to FAT/FAT32/NTFS/UDF/exFAT/ReFS/ext2/3/4, and writes MBR/PBR/bootloaders such as Syslinux and GRUB. It also implements Windows-specific features such as UEFI Secure Boot revocation updates, Windows To Go support, VSS snapshots, and dark-mode UI. Architecturally it is a classic monolithic C application: an autotools/VS build produces one executable with a Win32 dialog UI, a resource-based localization system, and tightly coupled modules for device enumeration, formatting, ISO mounting, and WIM application. The repo vendors a large collection of self-contained C libraries (wimlib, libcdio, ext2fs, ms-sys, syslinux libinstaller, bled decompression, getopt) and adapts them for Windows raw-block I/O. Runtime dependencies are Windows system DLLs, Microsoft symbol-server downloads, UEFI revocation databases, and optional network fetches of boot components. The project is actively maintained with CI workflows for VS2026 and MinGW, CodeQL, Coverity, and dependabot. Its code quality is characterized by defensive low-level Windows programming, careful handling of version-dependent APIs, and extensive real-hardware compatibility work. The main risk is technical drift: many vendored dependencies are snapshots of older upstream libraries, and several modules rely on undocumented or semi-documented Windows behavior.