Mezzano is an operating system written in Common Lisp.
The project addresses the challenge of building a complete, self-hosting operating system using a high-level language rather than traditional systems languages. It implements a full OS kernel, device drivers, file system support, and graphical user interface entirely in Common Lisp, demonstrating that such an approach can be practical. The system runs on x86-64 architecture with experimental AArch64 support, and can execute in virtual machines like VirtualBox and QEMU as well as on real hardware.
Mezzano suits developers interested in exploring alternative approaches to systems programming, language implementation, or those curious about what becomes possible when building an OS in Lisp rather than C or assembly. It is not a drop-in replacement for mainstream operating systems; it is a research and demonstration project. The README does not position it against other operating systems or provide comparative claims. Users should expect that running Mezzano on specific hardware or emulators often requires engagement with the codebase, as hardware support remains a work in progress.
The project shows active development across multiple areas including device drivers, file system implementations, compiler improvements, and standards conformance. Work spans USB stack development, EXT2/3/4 file system support, hardware-accelerated 3D graphics via Virgl, multicore support, and porting of substantial libraries like McCLIM and Quicklisp. The codebase demonstrates ongoing refinement of the garbage collector, CLOS implementation, and memory management strategies. Community participation occurs through an IRC channel, and the project accepts contributions addressing specific subsystems and features.
