Fiwix is an operating system kernel based on the UNIX architecture and fully focused on being POSIX compatible. It is designed and developed mainly as a hobbyist operating system, but it also serves for educational purposes. It runs on the i386 hardware platform and is compatible with a good base of existing GNU applications. It follows the UNIX System V application binary interface and is also mostly Linux 2.0 i386 system call ABI compatible.

The FiwixOS 3.5 operating system is a Fiwix distribution. It uses the Fiwix kernel, includes the GNU toolchain (GCC, Binutils, Make), it uses Newlib v4.5.0 as its C standard library, and Ext2 as its primary file system.

Between October 2022 and the whole 2023 the Fiwix kernel accepted a series of patches that were necessary to be able to be compiled with TCC. This was a necessary step into the whole bootstrapping process to build a complete Linux distribution from scratch, with Fiwix being currently a crucial part of it.

In January 2026 appeared a project that acts as a full-source bootstrap chain for NixOS

Features

Features according to the official website include:

• Written in ANSI C language (Assembly used only in the needed parts).

• GRUB Multiboot Specification v1 compliant.

• Full 32bit protected mode non-preemptive kernel.

• POSIX compliant (mostly).

• For i386 processors and higher.

• Process groups, sessions and job control.

• Interprocess communication with pipes, signals and UNIX-domain sockets.

• UNIX System V IPC (semaphores, message queues and shared memory).

• BSD file locking mechanism (POSIX restricted to whole file and advisory only).

• Virtual memory splits (user/kernel): 3GB/1GB and 2GB/2GB.

• Linux 2.0 ABI system calls compatibility (mostly).

• ELF-386 executable format support (statically and dynamically linked).

• Round Robin based scheduler algorithm (no priorities yet).

• VFS abstraction layer.

• Kexec support.

• Ext2 filesystem support with 1KB, 2KB and 4KB block sizes.

• Minix v1 and v2 filesystem support.

• Linux-like Proc filesystem support (read only).

• ISO9660 filesystem support with Rock Ridge extensions.

• RAMdisk device support.

• Initial RAMdisk (initrd) image support.

• SVGALib based applications support.

• PCI local bus support.

• UNIX98 pseudoterminals (pty) and devpts filesystem support.

• Virtual consoles support (up to 12).

• Keyboard driver with Linux keymaps support.

• PS/2 mouse support.

• Frame buffer device support for VESA VBE 2.0+ compliant graphic cards.

• Framebuffer console (fbcon) support.

• Serial port RS-232 driver support.

• Remote serial console support.

• QEMU Bochs-style debug console support.

• Basic implementation of a Pseudo-Random Number Generator.

• Floppy disk device driver and DMA management.

• IDE/ATA hard disk device driver.

• IDE/ATA ATAPI CD-ROM device driver.

References

Further reading

External links