Daniel Samson
67702fa250
Completes Phase 2: the FAT filesystem now stamps and reports a real modification time, built on the Phase 2d(i) kernel wall-clock. This is the last stat field the compiler's build cache needs to reason about (source vs cached output). - on-disk.zig: fatToEpoch / epochToFatDateTime convert between the two 16-bit DOS date/time fields and Unix epoch seconds (UTC — FAT has no timezone). Host-tested round-trip + an absolute check (1577836800 == 2020-01-01). - engine: a settable current_time_epoch that create/write stamp into the entry's write (and creation) date/time; Node/Listing gained an mtime decoded from those fields on read. Host test: a create stamps the mtime, read back through resolve and listEntry. - vfs protocol FileStatus + runtime.fs.Attributes gained an mtime field; the fat server sets current_time_epoch from runtime.system.wallClock() per request and returns mtime from stat. The flat ramfs reports 0 (it has no timestamps). - fat-test reads the created file's mtime through stat and checks it is a real current time, behind a new `fat-mtime` QEMU case. Verified against the host: the guest stamped mtime 1783971676 while the host clock was 1783971680 (boot+test lag) — the file's mtime is real current time. zig build, zig build test (the epoch<->DOS conversions + the engine mtime test), zig build check-fat-image, and a sequential QEMU sweep — fat-mount, fat-mutations, fat-rename, fat-mtime, vfs, vfs-client-death, log-flush, orderly-shutdown, initial-ramdisk, smoke, wall-clock, usb-storage — all green. mode/inode remain.
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 orzigupwill pick up.zig-versionautomatically. - QEMU (
qemu-system-x86_64) — to run and test the kernel. On macOS,brew install qemualso bundles the OVMF firmware below. - OVMF UEFI firmware — the
edk2-ovmfpackage (Arch),ovmf(Debian/Ubuntu), oredk2-ovmf(Fedora); on macOS it ships inside the Homebrewqemuformula. 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.
Logo
San Serif Text "Dan OS" with a black karate belt around it.