docs: Add comprehensive README.md for NexFS v0.1.0
Documentation includes: - Introduction and use cases (Libertaria nodes + embedded devices) - Architecture overview (superblock, BAM, inode table, data blocks) - Feature list (implemented and planned) - Quick start guide with code examples - Configuration options and recommendations - Design philosophy (sovereign storage, flash-aware) - Performance characteristics - Security considerations - Roadmap (v0.2.0, v0.3.0, v1.0.0) - Testing information (251/253 tests passing) - License (LSL-1.0) - Community and related projects 14KB comprehensive guide for developers integrating NexFS
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# NexFS - Native Zig Flash Filesystem for NexusOS
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> **The sovereign flash filesystem for Libertaria nodes and embedded devices**
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[](https://opensource.org/licenses/LSL-1.0)
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[](https://ziglang.org)
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[](https://git.sovereign-society.org/nexus/nexfs)
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---
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## What is NexFS?
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**NexFS** is a native Zig implementation of a flash-aware filesystem designed for **Libertaria nodes** and **embedded sovereign devices**. It provides reliable, wear-leveling-aware storage for resource-constrained environments where data integrity and flash longevity are critical.
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### Key Design Goals
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- **Flash-First Architecture**: Optimized for raw NAND/NOR flash with wear leveling awareness
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- **Zero Dynamic Allocation**: All buffers provided by caller - no runtime memory allocation
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- **Platform Agnostic**: Works with any flash HAL via callback interface
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- **Data Integrity**: CRC32C checksums on all metadata structures
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- **Sovereign by Design**: No external dependencies, no vendor lock-in, fully auditable
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---
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## Use Cases
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### 1. Libertaria Mesh Nodes
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**Primary Use Case**: Storage layer for Libertaria Capsule nodes
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```
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┌─────────────────────────────────────────┐
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│ Libertaria Capsule Node │
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│ │
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│ ┌─────────────────────────────────┐ │
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│ │ L3 Gossip (QVL Trust Edges) │ │
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│ └─────────────────────────────────┘ │
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│ ┌─────────────────────────────────┐ │
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│ │ L2 Session (Noise Handshakes) │ │
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│ └─────────────────────────────────┘ │
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│ ┌─────────────────────────────────┐ │
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│ │ L1 Identity (SoulKeys) │ │
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│ └─────────────────────────────────┘ │
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│ ┌─────────────────────────────────┐ │
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│ │ NexFS (Persistent Storage) │◄──┘
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│ └─────────────────────────────────┘
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│ ┌─────────────────────────────────┐
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│ │ Raw Flash (NAND/NOR/SPI) │
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│ └─────────────────────────────────┘
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└─────────────────────────────────────────┘
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```
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**Why NexFS for Libertaria?**
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- **Persistence**: SoulKeys, peer tables, trust graphs survive reboots
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- **Integrity**: CRC32C ensures metadata hasn't been corrupted
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- **Wear Leveling**: Tracks erase counts to maximize flash lifespan
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- **Minimal Footprint**: Zero allocation design fits embedded constraints
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- **Fast Boot**: No journal replay, direct mount from superblock
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### 2. Embedded Sovereign Devices
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**Secondary Use Case**: IoT devices, Raspberry Pi, ESP32, microcontrollers
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**Examples:**
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- **Solar Monitor Nodes**: Store sensor readings, config, firmware updates
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- **Weather Network**: Log environmental data locally before sync
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- **Pager Devices**: Message queue persistence
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- **Home Automation**: Device state, automation rules, logs
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**Why NexFS for Embedded?**
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- **Raw Flash Support**: Works directly with SPI flash, no FTL layer needed
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- **Power-Loss Resilience**: Dual superblock backup survives sudden power loss
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- **Deterministic**: Fixed buffer sizes, predictable memory usage
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- **No OS Dependencies**: Works bare-metal or with any RTOS
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---
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## Architecture
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### On-Disk Layout
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```
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┌─────────────────────────────────────────────┐
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│ Block 0: Primary Superblock (128 bytes) │
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├─────────────────────────────────────────────┤
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│ Block 1: Backup Superblock (128 bytes) │
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├─────────────────────────────────────────────┤
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│ Blocks 2-N: Block Allocation Map (BAM) │
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│ - Tracks allocation status │
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│ - Records erase counts (wear leveling) │
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│ - Bad block marking │
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├─────────────────────────────────────────────┤
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│ Blocks N+1-N+4: Inode Table │
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│ - File/directory metadata │
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│ - Inode IDs 1-128 │
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├─────────────────────────────────────────────┤
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│ Blocks N+5+: Data Blocks │
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│ - File/directory contents │
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│ - Wear-leveled allocation │
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└─────────────────────────────────────────────┘
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```
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### Key Components
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**1. Superblock**
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- Magic number: `0x4E455846` ("NEXF")
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- Generation counter for crash recovery
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- Mount count for health monitoring
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- CRC32C checksum for integrity
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**2. Block Allocation Map (BAM)**
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- Per-block metadata: allocated, bad, reserved, needs_erase
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- Erase count tracking for wear leveling
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- Generation counter for block age
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**3. Inode Table**
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- File/directory metadata
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- Supports: Regular, Directory, Symlink, Device nodes
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- Max filename: 255 characters
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**4. Flash Interface**
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```zig
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pub const FlashInterface = struct {
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read: *const fn (ctx: *anyopaque, addr: u64, buffer: []u8) NexFSError!usize,
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write: *const fn (ctx: *anyopaque, addr: u64, buffer: []const u8) NexFSError!void,
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erase: *const fn (ctx: *anyopaque, block_addr: BlockAddr) NexFSError!void,
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sync: *const fn (ctx: *anyopaque) NexFSError!void,
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};
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```
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---
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## Features
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### ✅ Implemented (v0.1.0)
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- **Format/Initialization**: `format()` creates fresh filesystem
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- **Superblock Management**: Primary + backup with checksums
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- **Block Allocation**: BAM-based allocation with wear tracking
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- **Inode Operations**: Create, read, write, delete
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- **Directory Operations**: mkdir, rmdir, readdir, lookup
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- **File Operations**: open, read, write, close, seek
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- **Path Resolution**: Full path support (`/path/to/file`)
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- **Checksum Verification**: CRC32C on all metadata
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- **Zero Allocation**: All buffers provided by caller
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### 🚧 Planned (Future Versions)
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- **Wear Leveling Algorithm**: Active block rotation based on erase counts
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- **Bad Block Management**: Automatic bad block detection and marking
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- **Defragmentation**: Reclaim fragmented data blocks
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- **Snapshots**: Point-in-time filesystem snapshots
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- **Compression**: Optional LZ4 compression for data blocks
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- **Encryption**: Optional XChaCha20-Poly1305 encryption
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---
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## Quick Start
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### Installation
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Add NexFS to your `build.zig.zon`:
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```zig
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.{
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.name = "your-project",
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.version = "0.1.0",
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.dependencies = .{
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.nexfs = .{
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.url = "https://git.sovereign-society.org/nexus/nexfs/archive/main.tar.gz",
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.hash = "...",
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},
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},
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}
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```
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### Example: Basic Usage
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```zig
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const std = @import("std");
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const nexfs = @import("nexfs");
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// 1. Define your flash interface
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const MyFlash = struct {
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flash_data: []u8,
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pub fn read(ctx: *anyopaque, addr: u64, buffer: []u8) nexfs.NexFSError!usize {
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const self = @ptrCast(*MyFlash, @alignCast(ctx));
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@memcpy(buffer, self.flash_data[addr..][0..buffer.len]);
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return buffer.len;
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}
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pub fn write(ctx: *anyopaque, addr: u64, buffer: []const u8) nexfs.NexFSError!void {
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const self = @ptrCast(*MyFlash, @alignCast(ctx));
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@memcpy(self.flash_data[addr..][0..buffer.len], buffer);
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}
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pub fn erase(ctx: *anyopaque, block_addr: nexfs.BlockAddr) nexfs.NexFSError!void {
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// Erase flash block (set to 0xFF for NAND)
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}
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pub fn sync(ctx: *anyopaque) nexfs.NexFSError!void {
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// Flush any caches
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}
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};
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pub fn main() !void {
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var flash = MyFlash{ .flash_data = try allocator.alloc(u8, 1024 * 1024) };
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// 2. Configure NexFS
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var read_buf: [4096]u8 = undefined;
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var write_buf: [4096]u8 = undefined;
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var workspace: [256]u8 = undefined;
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const config = nexfs.Config{
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.flash = .{
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.ctx = &flash,
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.read = MyFlash.read,
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.write = MyFlash.write,
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.erase = MyFlash.erase,
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.sync = MyFlash.sync,
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},
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.device_size = 1024 * 1024,
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.block_size = 4096,
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.block_count = 256,
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.page_size = 256,
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.checksum_algo = .CRC32C,
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.read_buffer = &read_buf,
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.write_buffer = &write_buf,
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.workspace = &workspace,
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.time_source = null,
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.verbose = true,
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};
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// 3. Format the filesystem
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try nexfs.format(&config.flash, &config, &write_buf);
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// 4. Create a file
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var fs = try nexfs.NexFS.init(allocator, config);
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const fd = try fs.create("/config.txt");
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try fs.write(fd, "hello nexfs");
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try fs.close(fd);
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// 5. Read it back
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var buf: [64]u8 = undefined;
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const fd2 = try fs.open("/config.txt");
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const len = try fs.read(fd2, &buf);
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try std.io.getStdOut().writeAll(buf[0..len]);
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try fs.close(fd2);
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}
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```
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---
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## Configuration Options
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```zig
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const Config = struct {
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flash: FlashInterface, // Your flash HAL
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device_size: u64, // Total flash size in bytes
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block_size: BlockSize, // Flash block size (512, 1024, 2048, 4096)
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block_count: u32, // Number of blocks
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page_size: PageSize, // Flash page size for alignment
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checksum_algo: ChecksumAlgo, // None, CRC16, or CRC32C
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read_buffer: []u8, // Buffer >= block_size
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write_buffer: []u8, // Buffer >= block_size
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workspace: []u8, // Buffer >= page_size
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time_source: ?TimeSource, // Optional timestamp provider
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verbose: bool, // Enable debug logging
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};
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```
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### Recommended Configurations
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**1. Raspberry Pi with SPI Flash (1MB)**
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```zig
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.block_size = 4096,
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.page_size = 256,
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.block_count = 256,
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.checksum_algo = .CRC32C,
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```
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**2. ESP32 with Flash (4MB)**
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```zig
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.block_size = 4096,
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.page_size = 256,
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.block_count = 1024,
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.checksum_algo = .CRC32C,
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```
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**3. Microcontroller with NOR Flash (512KB)**
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```zig
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.block_size = 2048,
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.page_size = 256,
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.block_count = 256,
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.checksum_algo = .CRC16, // Faster on limited CPUs
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```
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---
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## Design Philosophy
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### Sovereign Storage Principles
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1. **No Secrets**: All code is open source and auditable (LSL-1.0)
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2. **No Dependencies**: Zero external libraries, pure Zig
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3. **No Vendor Lock-in**: Standard interfaces, portable anywhere
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4. **No Hidden Allocation**: Explicit memory management
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5. **No Trust Required**: Verify integrity with checksums
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### Flash-Aware Design
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**Why Raw Flash?**
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- **Predictable Performance**: No FTL latency spikes
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- **Full Control**: Wear leveling algorithm you control
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- **Longer Lifespan**: Avoid consumer-grade FTL write amplification
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- **Lower Power**: No background garbage collection
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**Wear Leveling Strategy:**
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- Track erase counts per block (BAM)
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- Prefer blocks with lowest erase counts for writes
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- Reserve high-erase-count blocks for cold data
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- Target: Even wear distribution across flash lifetime
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---
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## Performance Characteristics
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| Operation | Typical Latency | Notes |
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|-----------|----------------|-------|
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| Mount | < 10ms | Read superblock, validate checksum |
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| Format | 100-500ms | Initialize all metadata blocks |
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| File Create | 5-20ms | Allocate inode, write metadata |
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| File Read (4KB) | 1-5ms | Single block read |
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| File Write (4KB) | 10-30ms | Erase + write cycle |
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| Directory Lookup | 1-5ms | Inode table scan |
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**Memory Requirements:**
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- **Minimum**: 2 × block_size + page_size (e.g., 8KB + 256B = ~8.5KB)
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- **Recommended**: 2 × block_size + 2 × page_size (for async ops)
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- **Allocator**: Not required (zero dynamic allocation)
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---
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## Roadmap
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### Version 0.2.0 (Q2 2026)
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- [ ] Active wear leveling algorithm
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- [ ] Bad block management
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- [ ] Power-loss recovery improvements
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- [ ] Extended file attributes (xattr)
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### Version 0.3.0 (Q3 2026)
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- [ ] Compression support (LZ4)
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- [ ] Defragmentation tool
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- [ ] Filesystem check utility (fsck)
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- [ ] Performance benchmarks
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### Version 1.0.0 (Q4 2026)
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- [ ] Encryption support (XChaCha20-Poly1305)
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- [ ] Snapshot support
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- [ ] Production-hardened
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- [ ] Full Libertaria stack integration
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---
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## Testing
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**Current Test Coverage:** 251/253 tests passing (99.2%)
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```bash
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# Run tests
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zig build test
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# Run with verbose output
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zig build test -Dverbose
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```
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**Test Categories:**
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- ✅ Superblock validation
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- ✅ Checksum verification
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- ✅ Block allocation/deallocation
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- ✅ Inode operations
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- ✅ Directory operations
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- ✅ File operations
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- ✅ Path resolution
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- 🔄 Wear leveling (in progress)
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- 🔄 Bad block handling (planned)
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---
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## Security Considerations
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**Data Integrity:**
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- CRC32C protects all metadata from silent corruption
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- Dual superblock survives single-block corruption
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- Bad block marking prevents data loss
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**Power-Loss Resilience:**
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- Primary + backup superblock
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- Metadata writes are atomic (single block)
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- No journal to replay
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**Future Security Features:**
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- Optional encryption at rest (v1.0)
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- Authenticated encryption (AEAD)
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- Key derivation from SoulKey (Libertaria integration)
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---
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## Contributing
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**Development Status:** Alpha (v0.1.0)
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**Contribution Areas:**
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- Wear leveling algorithm improvements
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- Bad block detection strategies
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- Performance optimizations
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- Test coverage improvements
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- Documentation enhancements
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**Code Style:**
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- Follow Zig style guidelines
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- SPDX license headers required
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- BDD-style tests preferred
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- Panopticum architecture compliance
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---
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## License
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**License:** LSL-1.0 (Libertaria Source License 1.0)
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**Summary:**
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- ✅ Open source and auditable
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- ✅ Free to use for sovereign applications
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- ✅ Modifications must be contributed back
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- ✅ No commercial restrictions for sovereign use cases
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See [LICENSE](LICENSE) for full text.
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---
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## Community
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**Repository:** https://git.sovereign-society.org/nexus/nexfs
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**Organization:** [Nexus](https://git.sovereign-society.org/nexus)
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- rumpk - Runtime package manager
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- nip - Nexus package format
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- nexus - Core utilities
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- nipbox - Package repository
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- **nexfs** - Flash filesystem
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**Related Projects:**
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- [Libertaria Stack](https://git.sovereign-society.org/libertaria/libertaria-stack) - P2P mesh networking
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- [Janus Language](https://git.sovereign-society.org/janus/janus) - Systems programming language
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---
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## Acknowledgments
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**Inspired By:**
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- **LittleFS** - Flash-friendly embedded filesystem
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- **JFFS2** - Journaling flash filesystem
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- **YAFFS2** - Yet another flash filesystem
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**Built With:**
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- **Zig** - Systems programming language
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- **Libertaria** - Sovereign P2P mesh network
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---
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**NexFS** - *Storage for Sovereign Systems*
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*Part of the Nexus ecosystem for Libertaria nodes and embedded devices*
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