GuardBSD

Rust Multi-Microkernel OS • Capability Security • Production-Ready

Website • GitHub • X (@GuardBSD)

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Overview

GuardBSD is a multi-microkernel operating system in Rust with capability-based security, TCB < 8,000 lines, full storage stack, and a 100% BSD-licensed bootloader.

Winter Saga - the first production-ready release:

• GuaBoot: 100% BSD bootloader (BIOS + UEFI), <1 second, ~60 KB
• gsh: zsh-level shell (scripting, job control, tab completion)
• GuardFS + GuardZFS: native FS + ZFS features in 1,543 lines
• 23 partition types, swap, ATA, block cache
• API Reference and Architecture Docs - fully documented

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Key Features

Component	Status	Description
GuaBoot	Production-Ready	100% BSD, BIOS/UEFI, ELF64, FreeBSD protocol, ~2,650 LOC
gsh Shell	Production-Ready	zsh-level: history, job control, scripts, aliases, functions
GuardZFS	Production-Ready	Pools, RAID-Z1/Z2, COW, snapshots, SHA-256, 1,543 LOC
GuardFS	Production-Ready	Journaling, snapshots, LZ4, COW, ~3,200 LOC
Disk I/O	Production-Ready	ATA, cache (128 blocks), 23 partition types, swap
Swap	Production-Ready	Auto-detection, up to 4, swapon/swapoff
Three Microkernels	FOSDEM 2026	µK-Time, µK-Space, µK-IPC - source closed until premiere

Microkernels are not public - world premiere at FOSDEM 2026

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Quick Start

# Clone
git clone https://github.com/Cartesian-School/guardbsd
cd guardbsd

# Build ISO
make iso

# Run
qemu-system-x86_64 -cdrom build/x86_64/guardbsd-winter-saga.iso -m 2G -smp 4 -serial stdio

ISO: guardbsd.org/download

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GuaBoot - 100% BSD Bootloader

No GRUB. No Multiboot. Only BSD.

BIOS → guaboot1 (512B) → guaboot2 (~32KB) → Long Mode → kernel.elf
UEFI → guaboot.efi (~50KB) → kernel.elf

• BIOS + UEFI
• 64-bit native
• ELF64 PT_LOAD
• E820 / UEFI memory map
• BootInfo (FreeBSD-compatible)
• Serial debug (COM1)
• ~2,650 lines (C + ASM)

RDI = 0x42534447 ("GBSD")
RSI = *BootInfo

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gsh - Full-Featured Shell (zsh-level)

$ zfs create tank/data
$ ls | grep txt > result.txt
$ sleep 10 &
$ jobs; fg %1
$ alias ll='ls -la'
$ greet() { echo "Hi, $1"; }; greet World

• History: ↑↓, Ctrl+R, !123
• Job Control: &, fg, bg, jobs
• Pipes: |, >, >>, <, 2>
• Scripts: #!/usr/bin/gsh
• Tab Completion: commands, paths, variables

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Filesystems

Feature	GuardFS	GuardZFS
Journaling	Yes	Yes (TXG)
Snapshots	Yes	Yes
Compression	Yes (LZ4)	Yes (LZ4)
Pool	No	Yes
RAID-Z	No	Yes (Z1/Z2)
Self-Healing	No	Yes (SHA-256)
Code	~3.2K LOC	1.5K LOC

zfs create tank/data
mkfs.guardfs /dev/disk0p2
mount -t guardfs /dev/disk0p2 /mnt

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Disk & Storage

• 23 partition types: FAT, NTFS, ext4, FreeBSD, HFS+, GPT, EFI
• Swap: up to 4, swapon 0, auto-detection
• ATA: LBA48, PIO, IDENTIFY
• Cache: 128 × 4KB, LRU, write-back

Partition 1: Linux Swap - 2048 MB [Swap]
Partition 2: GuardZFS - 20480 MB

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Architecture

┌────────────────────────────────────────────┐
│             User Applications              │
├────────────────────────────────────────────┤
│    gsh │ zfs │ mkfs.guardfs │ top          │
├────────────────────────────────────────────┤
│  VFS │ GuardFS │ GuardZFS │ Init │ NetD    │
├────────────────────────────────────────────┤
│   µK-Space   │   µK-Time   │   µK-IPC      │
├────────────────────────────────────────────┤
│              System Call Layer             │
├────────────────────────────────────────────┤
│                  GuaBoot                   │
└────────────────────────────────────────────┘

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API Reference

Full API - docs/api/REFERENCE.md

Examples

// IPC
let port = port_create()?;
ipc_send(port, &Message::new(1, b"ping"))?;

// Files
let fd = open("/data", O_RDWR)?;
write(fd, b"GuardBSD")?;
close(fd)?;

// Memory
let paddr = pmm_alloc()?;
vmm_map(0x100000, paddr, READ | WRITE)?;

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System Requirements

	Minimum	Recommended
CPU	x86_64	dual-core
RAM	256 MB	2 GB
Disk	1 GB	4 GB+
Boot	UEFI/BIOS	UEFI

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Building

# Debian/Ubuntu
sudo apt install build-essential rustc cargo qemu-system-x86 xorriso gnu-efi nasm

rustup target add x86_64-unknown-none

make iso
make test-boot

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Roadmap

Milestone	Date	Status
Winter Saga	Jan 2026	Done
FOSDEM 2026	Feb 2026	Planned
Microkernels Open	Post-FOSDEM	Planned
ARM64	Q2 2026	In Progress
RISC-V	Q3 2026	Planned

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Documentation

• guardbsd.org – ISO, news
• gsh Manual – docs/shell/gsh-manual.md
• GuaBoot Reference – boot/guaboot/REFERENCE.md
• API Reference – docs/api/REFERENCE.md
• Architecture – docs/architecture/OVERVIEW.md

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Performance

Metric	Value
GuaBoot	< 1 s
Bootloader	~60 KB
Memory	~50 MB
Context	< 1 µs
IPC	~180 cycles
GuardZFS	~50 MB/s (SHA-256)
GuardFS	~500 MB/s (LZ4)

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License

BSD 3-Clause License
Copyright (c) 2025 Siergej Sobolewski, Cartesian School

LICENSE

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Contributing

• CONTRIBUTING.md
• Open an Issue / PR

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Community

• Web: https://www.guardbsd.org
• GitHub: https://github.com/Cartesian-School/guardbsd
• X: @GuardBSD
• Email: [email protected]
• FOSDEM 2026: Microkernel Devroom - microkernel premiere

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Status

Version: 1.0.0
Status: Active Development
License: BSD 3-Clause
Platforms: x86_64, AArch64

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GuardBSD - Secure, Fast, Modern