# System Architecture Design Guide

## Overview
This document combines research on advanced architecture, daemon design, and critical integration for apt-ostree.

## Advanced Architecture Research

### Core Principles
- **Modular design**: Separate concerns into distinct modules
- **Interface abstraction**: Clean interfaces between components
- **Error handling**: Comprehensive error management
- **Security model**: Privilege separation and authentication

### Component Architecture
- **CLI layer**: User interface and command parsing
- **Daemon layer**: Privileged operations and state management
- **Integration layer**: APT-OSTree coordination
- **Storage layer**: OSTree and package management

## Daemon Architecture

### Design Philosophy
- **Privilege separation**: Root operations isolated in daemon
- **D-Bus communication**: Standard system service interface
- **Service activation**: Systemd integration
- **State management**: Centralized system state

### Implementation
- **apt-ostreed**: Main daemon process
- **D-Bus interface**: Service communication protocol
- **Policy management**: Security and access control
- **Transaction handling**: Atomic operation management

### D-Bus Interface
- **org.aptostree.dev**: Service interface
- **Method definitions**: Package management operations
- **Signal handling**: State change notifications
- **Error reporting**: Comprehensive error information

## Critical Integration

### APT-OSTree Coordination
- **Package installation**: APT operations in OSTree context
- **State synchronization**: Keep databases in sync
- **Transaction management**: Atomic package operations
- **Rollback support**: Complete system rollback

### Bubblewrap Integration
- **Script sandboxing**: Secure package script execution
- **Namespace isolation**: Process isolation
- **Bind mounts**: Controlled filesystem access
- **Security controls**: Privilege restrictions

### Filesystem Management
- **OSTree operations**: Commit creation and management
- **Layer application**: Package layer integration
- **Deployment management**: Boot configuration
- **State tracking**: System state monitoring

## Implementation Strategy

### Phase 1: Foundation
- Basic daemon-client architecture
- D-Bus communication setup
- Security policy configuration
- Error handling framework

### Phase 2: Integration
- APT package management integration
- OSTree filesystem operations
- Transaction management
- Rollback implementation

### Phase 3: Advanced Features
- Bubblewrap sandboxing
- Advanced security features
- Performance optimization
- Comprehensive testing

## Technical Details

### D-Bus Communication
- Service registration and activation
- Method call handling
- Signal emission and reception
- Error propagation

### Security Model
- Privilege separation
- Access control policies
- Sandboxing implementation
- Audit logging

### State Management
- System state tracking
- Transaction state management
- Rollback state preservation
- Configuration management

## References
- See .notes/research/advanced-architecture.md for detailed architecture research
- See .notes/research/daemon.md for daemon architecture details
- See .notes/rpm-ostree/daemon-client-architecture.md for rpm-ostree daemon analysis
- See .notes/critical_integration_implementation.md for critical integration details 