daniel
/
danos
1
0
Fork 0
Code Issues 4 Pull Requests Actions Packages Projects 1 Releases Wiki Activity
Operating System written for me
193 Commits 19 Branches 0 Tags 41 MiB
Zig 94.2%
Python 4.7%
Assembly 1.1%
Go to file
Daniel Samson 53e42837e0
Docs: add the Zig self-hosting roadmap 
A forward-looking design note on making danos a real Zig target
(-target x86_64-danos) and eventually running the compiler on it, focused on
the standard-library surface (not the editor/terminal).

The core realisation: Zig 0.16 (post-writergate) collapses an OS port to ONE
seam — std.fs is gone, everything routes through the std.Io vtable, and
std.posix is generic over a single per-OS `system` module (std.os.<tag>). So the
port is "write std.os.danos once" and the whole fs/process/Io tower lights up,
rather than reimplementing the namespaces.

Records the decisions this shapes now: build runtime.os (the seam, promoted into
a forked std/os/danos.zig later) plus a thin runtime.fs; retire the premature
library/posix shim (only 5 unistd call sites); do NOT hand-mirror the high-level
std namespaces; do NOT emulate the Linux ABI; defer musl. Covers the host/target/
self-host roles and the four-part compiler fork, a coverage table of what danos
has vs the gaps (mkdir/unlink/rename/truncate, richer stat, wall-clock, env, cwd,
entropy, stdio bytes), a phased plan (target -> read-side+retire-posix ->
fs-mutation+stat -> single-threaded self-linked compiler), and the risks
(fork rebase treadmill, -fsingle-threaded and -fno-llvm/-fno-lld being
load-bearing, the "w"-does-not-truncate corruption bug). Linked from the docs index.
 		2026-07-13 19:26:51 +01:00
boot fix efi: debug prefix 2026-07-13 05:30:56 +01:00
docs Docs: add the Zig self-hosting roadmap 2026-07-13 19:26:51 +01:00
library Persist the kernel boot log to the USB FAT volume 2026-07-13 18:18:34 +01:00
system Persist the kernel boot log to the USB FAT volume 2026-07-13 18:18:34 +01:00
test Persist the kernel boot log to the USB FAT volume 2026-07-13 18:18:34 +01:00
tools M7: in-repo FAT32 image builder + boot the whole system off a USB stick 2026-07-13 15:34:18 +01:00
.editorconfig editorconfig 2026-07-12 16:09:11 +01:00
.gitattributes gitattributes 2026-07-12 16:09:18 +01:00
.gitignore gitignore: ignore .claude/ and .github/ 2026-07-10 14:09:38 +01:00
.zig-version Pin zig version to 0.16 LTS 2026-07-03 13:49:47 +01:00
README.md Docs: link README to system-requirements.md 2026-07-13 11:10:24 +01:00
build.zig Persist the kernel boot log to the USB FAT volume 2026-07-13 18:18:34 +01:00
build.zig.zon started project with basic efi setup 2026-07-01 18:32:56 +01:00

README.md

DanOS

Codename: Shodan Version: 1

A small resilient operating system, written from scratch in Zig.

Zen of DanOS:

  • Resilient Micro-Kernel Architecture.
    • Every process run in an isolated user space not kernel space.
    • Processes cannot take down the entire OS with it when they die or is killed
  • Stable public runtime library, private OS ABI.
    • Keeps a stable runtime for user space processes between OS versions (great for backwards compatibility)
    • Allows the underlying OS to be changed without effecting applications
    • Provides a boundary to enable compatibility between OS's e.g. POSIX, MUSL etc
  • Drivers are just isolated processes in user space.
    • Thin binaries that can be restarted like applications.
    • Useful during driver development.
    • Drivers can claim MMIO / ports
    • Driver resources (e.g. IRQ/Port/MMIO) claims are automatically cleaned up if the driver dies or is killed
    • Drivers can also hook into the process lifecyle to clean up or reset hardware
  • No legacy to deal with
    • Zig code uses a clean coding style (Zen of Zig)
    • Favor reading code over writing code.
    • No magic numbers.
    • No shortend names unless its for ABI compatibility or acronyms
  • Inter-Process Communication (IPC)
    • Publish and subscribe to Asynchronous Messages
    • Talk to services and processes synchronously

Prerequisites

  • Zig 0.16.x — the build is pinned to this line (.zig-version); other minor versions are rejected, because Zig makes breaking changes between releases pre-1.0. A toolchain manager such as zvm or zigup will pick up .zig-version automatically.
  • QEMU (qemu-system-x86_64) — to run and test the kernel. On macOS, brew install qemu also bundles the OVMF firmware below.
  • OVMF UEFI firmware — the edk2-ovmf package (Arch), ovmf (Debian/Ubuntu), or edk2-ovmf (Fedora); on macOS it ships inside the Homebrew qemu formula. Both the build and the test harness probe the known Arch/Debian/Fedora/macOS layouts and use the first that exists, so no configuration is normally needed. Override with -Dovmf-code= / -Dovmf-vars= (build) if yours lives elsewhere.
  • Python 3 — for the QEMU integration test harness.

Build

zig build

Produces a FHS-shaped zig-out/ that is the danos filesystem and the boot volume: the UEFI bootloader at zig-out/EFI/BOOT/BOOTX64.efi, the kernel at zig-out/system/kernel, init at zig-out/system/services/init, drivers under zig-out/system/drivers/, and the initial-ramdisk at zig-out/boot/.

Run

Boot it in QEMU with OVMF (opens a display window):

zig build run-x86-64
# distro with OVMF elsewhere:
zig build run-x86-64 -Dovmf-code=/path/OVMF_CODE.fd -Dovmf-vars=/path/OVMF_VARS.fd

Test

zig build test            # host unit tests (the platform-independent shared code)
python3 test/qemu_test.py  # QEMU integration tests: boots the kernel and asserts
                           # on its serial output (see docs/testing.md)

The integration harness builds and boots the kernel once per test case, checking memory, the frame allocator, paging (incl. NX and the null guard), the heap, interrupts, and exception handling. It exits non-zero on any failure, so it drops straight into CI.

Documentation

Design notes explaining why behind the code live in docs/ — start with docs/README.md.

For the hardware needed to run DanOS — minimum specs plus a plain-language guide matching Intel/AMD CPU generations by name — see docs/system-requirements.md.

San Serif Text "Dan OS" with a black karate belt around it.