# System Management Architecture

## Overview

This document describes the system management architecture for `apt-ostree`, covering how the system handles initramfs management, kernel arguments, daemon operations, and other system-level functionality. The design maintains compatibility with `rpm-ostree` while integrating with Debian/Ubuntu system components.

## System Management Commands

### Initramfs Management

#### `apt-ostree initramfs`
Manages the initial RAM filesystem for the current deployment.

**Implementation Details:**
- Regenerates initramfs for current kernel
- Includes OSTree-specific modules
- Updates bootloader configuration
- Maintains kernel module dependencies

**Example:**
```bash
apt-ostree initramfs
```

**Options:**
- `--force` - Force regeneration even if unchanged
- `--verbose` - Show detailed output
- `--debug` - Enable debug mode

#### `apt-ostree initramfs-etc`
Manages `/etc` files in the initramfs.

**Implementation Details:**
- Copies relevant `/etc` files to initramfs
- Maintains configuration consistency
- Updates initramfs when `/etc` changes
- Handles configuration file conflicts

**Example:**
```bash
apt-ostree initramfs-etc
```

### Kernel Arguments Management

#### `apt-ostree kargs`
Manages kernel command line arguments.

**Implementation Details:**
- Reads current kernel arguments
- Modifies kernel arguments for deployments
- Updates bootloader configuration
- Maintains argument persistence across reboots

**Example:**
```bash
# View current kernel arguments
apt-ostree kargs

# Add kernel argument
apt-ostree kargs --append="console=ttyS0"

# Remove kernel argument
apt-ostree kargs --delete="console=ttyS0"

# Replace kernel argument
apt-ostree kargs --replace="console=ttyS0,115200"
```

**Options:**
- `--append` - Add new kernel argument
- `--delete` - Remove kernel argument
- `--replace` - Replace kernel argument
- `--deploy-index` - Target specific deployment
- `--print-only` - Show what would be changed

### Daemon Management

#### `apt-ostree reload`
Reloads the daemon configuration and state.

**Implementation Details:**
- Reloads configuration files
- Refreshes package lists
- Updates transaction state
- Restarts background services

**Example:**
```bash
apt-ostree reload
```

#### `apt-ostree cancel`
Cancels pending transactions.

**Implementation Details:**
- Identifies active transactions
- Cancels pending operations
- Cleans up temporary files
- Restores system state

**Example:**
```bash
apt-ostree cancel
```

**Options:**
- `--transaction-id` - Cancel specific transaction
- `--all` - Cancel all pending transactions

## System Architecture

### Initramfs Integration

The initramfs system integrates with OSTree deployments:

```
Boot Process:
1. Bootloader loads kernel + initramfs
2. Initramfs mounts OSTree root
3. System switches to OSTree deployment
4. Normal system initialization
```

**Components:**
- **Kernel modules** - Required for boot
- **OSTree tools** - Deployment management
- **Configuration files** - System settings
- **Helper scripts** - Boot automation

### Kernel Arguments Persistence

Kernel arguments are stored and managed per deployment:

```
Deployment Structure:
├── OSTree commit
├── Kernel arguments
├── Bootloader config
└── Initramfs reference
```

**Storage:**
- **OSTree metadata** - Argument storage
- **Bootloader integration** - GRUB/GRUB2 support
- **Deployment linking** - Argument association

### Daemon State Management

The daemon maintains system state:

```
Daemon State:
├── Active transactions
├── Package cache
├── OSTree status
├── Configuration
└── System health
```

## Integration Points

### Bootloader Integration

Supports multiple bootloaders:

- **GRUB2** - Primary bootloader
- **systemd-boot** - UEFI bootloader
- **Extlinux** - Legacy bootloader

**Configuration:**
- Automatic bootloader detection
- Configuration file generation
- Boot entry management
- Default boot selection

### Systemd Integration

Integrates with systemd services:

- **Service management** - Start/stop/restart
- **Dependency handling** - Service ordering
- **Logging integration** - Journald support
- **Socket activation** - DBus communication

### OSTree Integration

Deep integration with OSTree:

- **Deployment management** - Current/previous deployments
- **Commit tracking** - Change history
- **Rollback support** - System restoration
- **Layering** - Package management

## Security Considerations

### Privilege Management

System management commands require elevated privileges:

- **Root access** - System-level changes
- **Polkit authorization** - Policy-based access control
- **Capability checking** - Linux capabilities
- **Audit logging** - Security event tracking

### Configuration Security

Protects system configuration:

- **File permissions** - Secure file access
- **Configuration validation** - Input sanitization
- **Change verification** - Integrity checking
- **Rollback protection** - Unauthorized change prevention

## Performance Optimization

### Caching Strategy

Implements intelligent caching:

- **Configuration cache** - Parsed configuration
- **State cache** - System state information
- **Metadata cache** - OSTree metadata
- **Bootloader cache** - Boot configuration

### Background Operations

Non-blocking system operations:

- **Async processing** - Non-blocking operations
- **Background updates** - Concurrent processing
- **Progress reporting** - User feedback
- **Error handling** - Graceful failure

## Error Handling

### Common Error Scenarios

1. **Initramfs Generation Failures**
   - Kernel module issues
   - Configuration conflicts
   - Disk space problems
   - Permission errors

2. **Kernel Argument Issues**
   - Invalid arguments
   - Bootloader errors
   - Configuration conflicts
   - Persistence failures

3. **Daemon Problems**
   - Service failures
   - Configuration errors
   - Resource exhaustion
   - Communication failures

### Recovery Mechanisms

Automatic and manual recovery:

- **Automatic rollback** - Failed operation recovery
- **State restoration** - Previous state recovery
- **Error reporting** - Detailed error information
- **Recovery guidance** - User assistance

## Monitoring and Logging

### System Health Monitoring

Continuous system monitoring:

- **Service status** - Daemon health
- **Transaction state** - Operation progress
- **Resource usage** - System resources
- **Error rates** - Failure tracking

### Logging Strategy

Comprehensive logging:

- **Structured logging** - JSON-formatted logs
- **Log levels** - Debug, info, warn, error
- **Log rotation** - Automatic log management
- **Log aggregation** - Centralized logging

## Integration with rpm-ostree

### Command Compatibility

Maintains 1:1 CLI compatibility:

- **Identical commands** - Same command names
- **Same options** - Compatible flags
- **Exit codes** - Identical exit codes
- **Error messages** - Compatible output

### Feature Parity

Core system management features match:

- **Initramfs management** - Same functionality
- **Kernel arguments** - Identical behavior
- **Daemon operations** - Compatible operations
- **System integration** - Similar integration points

## Future Enhancements

### Planned Features

1. **Advanced Boot Management**
   - Boot time optimization
   - Boot failure recovery
   - Boot performance monitoring
   - Custom boot scripts

2. **Enhanced Monitoring**
   - Real-time system monitoring
   - Performance metrics
   - Health check automation
   - Predictive maintenance

3. **Configuration Management**
   - Configuration templates
   - Environment-specific configs
   - Configuration validation
   - Change tracking

4. **Security Enhancements**
   - Enhanced access control
   - Security policy enforcement
   - Vulnerability scanning
   - Security auditing

## Implementation Notes

### Current Status

- Basic system management implemented
- Initramfs management functional
- Kernel argument handling working
- Daemon operations operational

### Next Steps

1. **Advanced Features**
   - Enhanced boot management
   - Advanced monitoring
   - Configuration templates
   - Security enhancements

2. **Performance Optimization**
   - Caching improvements
   - Background processing
   - Resource optimization
   - Boot time reduction

3. **Testing and Validation**
   - Comprehensive testing
   - Performance benchmarking
   - Security auditing
   - Integration testing
