RADPx-OS (Radical Posix OS) is a POSIX-inspired operating system kernel aimed at embedded boards, desktop VM testing, and future SoC targets. The Crimson 0.1.4 package line keeps an RTOS-influenced bias toward explicit subsystems while exposing familiar process, file, device, terminal, framebuffer, filesystem, and driver APIs.

This hub documents the experimental Crimson 0.1.4 kernel/package API surface.

Start Here

Getting Started walks a fresh checkout to a booted image on x86_64 and the ZuBoard-1CG A53 (QEMU).
Architecture & Layout maps the source tree — core, fs, drivers, platforms, boards, runtime, and hal.
API Structure explains the public ABI shape and subsystem ownership.
API Groups provides a subsystem-oriented API index.
Overlay And Device Tree Guide documents the runtime overlay/device-tree model.
RADCompositor describes the experimental Slint/RADCompositor windowing path.
Experimental Networking describes the experimental IPv4/UDP and TCP stream socket foundation.
RadBuild Integration describes the RadBuild 0.2.1 OS build and artifact publication flow.
Pi Zero 2 W Bring-Up tracks the experimental two-stage Pi Zero 2 W bring-up.
Minimal Examples provides short driver, framebuffer, input, VFS, and syscall examples.
Crimson 0.1.4 Status separates stable-beta APIs from incomplete areas.

API Groups

Kernel lifecycle, boot handoff, printk, CPU control, time, memory, and performance counters.
Tasks, scheduler state, wait queues, mutexes, events, and timer sources.
Processes, file descriptors, syscall dispatch, programs, and POSIX-inspired VFS, shared-memory, and memory-mapping entry points.
Device registry, ioctl, block, network, framebuffer/display, input, TTY, PTY, audio, and serial APIs.
Experimental IPv4/UDP datagram and local TCP stream socket support for the x86 VM path.
Experimental Pi Zero 2 W bcm283x_pi payload and handoff ABI.
Overlay tree, IRQ domains/resources, modules, I2C, SPI, and DMA driver APIs.

Filesystem and Package Profile

The x86_64 VM target currently boots from ext4. Crimson 0.1.4 supports a clean no-journal read/write ext4 profile with extent-backed files, allocation, create, mkdir, rename, truncate, symlink/readlink, unlink, rmdir, chmod, and fsync. Journal replay and journaled metadata commits are intentionally outside the current beta profile.

RadBuild stages RADPx-OS packages through RadicalPackages .radpm packagegroups. The standard terminal image selects rad-terminal-base and can add rad-networking; RADCompositor images select rad-desktop-base.

Verification

Host kernel tests:

cmake -S . -B build-host -DRADPX_OS_BUILD_TESTS=ON
cmake --build build-host -j2
./build-host/tests/RADKernelTests

x86_64 GRUB + Slint VM smoke:

tools/embedded/x86_64_grub_slint_smoke.sh

Canonical RadBuild OS build:

radbuild build os --settings settings.json --json-events

Current experimental x86 bundles and .radpm packages are published through the RadicalPackages GitHub Releases and package indexes.