# OSTree Filesystem Integration Guide

## Overview
This document combines research on OSTree, atomic filesystems, and live layering for apt-ostree integration.

## OSTree Filesystem Research

### Core Concepts
- **Content-addressed storage**: Files identified by content hash
- **Atomic commits**: All-or-nothing filesystem changes
- **Deployment management**: Multiple bootable filesystem versions
- **Rollback support**: Instant reversion to previous state

### Key Components
- **ostree**: Core filesystem management tool
- **libostree**: OSTree library for programmatic access
- **ostree-admin**: System administration commands
- **ostree-repo**: Repository management

## Atomic Filesystems

### Principles
- **"From Scratch" Philosophy**: Every change regenerates target filesystem completely
- **No hysteresis**: State-independent behavior
- **Reproducible results**: Consistent outcomes
- **System consistency**: Maintained integrity

### Implementation
- Complete filesystem regeneration
- Atomic transaction handling
- Rollback capability
- State synchronization

## Live Layering

### Concept
- **Immutable base**: Base image remains unchanged
- **Layered packages**: User packages layered on top
- **Clear separation**: Base vs. user content distinction

### Benefits
- Predictable behavior
- Easy rollback
- Consistent deployments
- Simplified debugging

## Integration Strategy

### Filesystem Assembly
- OSTree commit extraction
- Package layer application
- Filesystem assembly
- Boot configuration

### Transaction Management
- Atomic operations
- Rollback support
- State tracking
- Error recovery

### Deployment Workflow
1. Create OSTree commit from base
2. Apply package layers
3. Generate deployment
4. Update bootloader
5. Activate deployment

## Technical Implementation

### OSTree Integration
- Commit creation and management
- Deployment tracking
- Rollback implementation
- Repository management

### Package Layer Management
- Layer creation and application
- Dependency resolution
- Conflict handling
- State synchronization

### Boot Integration
- GRUB/systemd-boot configuration
- Kernel parameter management
- Initramfs handling
- Boot verification

## References
- See .notes/research/ostree.md for detailed OSTree research
- See .notes/research/atomic-filesystems.md for atomic filesystem concepts
- See .notes/research/live-layering.md for live layering techniques
- See .notes/research/composefs.md for Composefs research 