apt-ostree/docs/.old/apt-ostree-daemon-plan/architecture/live-updates.md

Live Updates Architecture

Overview

This document describes the live updates architecture for apt-ostree, covering how the system handles live updates, user overlays, and runtime modifications without requiring system reboots. The design enables dynamic system updates while maintaining system stability and consistency.

Live Update Commands

Core Live Update Commands

apt-ostree apply-live

Applies live updates to the running system.

Purpose:

• Apply package updates without reboot
• Update system configuration
• Modify running services
• Apply security patches

Implementation Details:

• Package installation in user space
• Service restart and reload
• Configuration file updates
• Runtime state management

Example:

# Apply live updates
apt-ostree apply-live

# Apply specific package updates
apt-ostree apply-live --packages=nginx,postgresql

# Apply with service restart
apt-ostree apply-live --restart-services

Options:

• --packages: Specific packages to update
• --restart-services: Restart affected services
• --dry-run: Show what would be updated
• --force: Force update even if risky

apt-ostree usroverlay

Manages user overlays for live modifications.

Purpose:

• Create temporary file overlays
• Modify system files at runtime
• Test configuration changes
• Apply temporary fixes

Implementation Details:

• Overlay filesystem creation
• File modification tracking
• Change persistence management
• Overlay cleanup and removal

Example:

# Create user overlay
apt-ostree usroverlay --create

# Add file to overlay
apt-ostree usroverlay --add=/etc/nginx/nginx.conf

# Remove overlay
apt-ostree usroverlay --remove

Options:

• --create: Create new overlay
• --add: Add file to overlay
• --remove: Remove overlay
• --list: List overlay contents

Live Update Architecture

Overlay Filesystem System

Overlay Structure

The live update system uses overlay filesystems:

System Structure:
├── Base OSTree (read-only)
├── User Overlay (read-write)
└── Runtime Modifications (temporary)

Components:

• Base layer: Original OSTree deployment
• User overlay: Persistent user modifications
• Runtime layer: Temporary runtime changes
• Union mount: Combined filesystem view

Overlay Types

1. User Overlays

   • Persistent across reboots
   • User-specific modifications
   • Configuration customizations
   • Package additions

2. Runtime Overlays

   • Temporary modifications
   • Service state changes
   • Configuration updates
   • Package installations

3. System Overlays

   • System-wide modifications
   • Service configurations
   • Security updates
   • System customizations

Live Update Process

Update Workflow

1. Update Detection

   • Check for available updates
   • Validate update compatibility
   • Assess update impact
   • Determine update strategy

2. Update Preparation

   • Download update packages
   • Verify package integrity
   • Check dependencies
   • Prepare update environment

3. Update Application

   • Apply package updates
   • Update configuration files
   • Restart affected services
   • Update system state

4. Update Verification

   • Verify update success
   • Check system stability
   • Validate functionality
   • Update completion status

Service Management

Service Updates:

• Configuration updates: Modify service configs
• Service restarts: Restart modified services
• Dependency updates: Update service dependencies
• State management: Maintain service state

Update Strategies:

• Hot reload: Reload configuration
• Graceful restart: Restart with minimal downtime
• Full restart: Complete service restart
• Rolling update: Update services incrementally

User Overlay System

Overlay Management

Overlay Creation

# Create new overlay
apt-ostree usroverlay --create --name=my-overlay

# Create overlay with specific scope
apt-ostree usroverlay --create --scope=system --name=system-overlay

Overlay Properties:

• Name: Unique overlay identifier
• Scope: Overlay scope (user, system, global)
• Persistence: Persistence across reboots
• Priority: Overlay priority level

Overlay Operations

File Operations:

• Add files: Add files to overlay
• Modify files: Modify existing files
• Remove files: Remove files from overlay
• List files: List overlay contents

Overlay Management:

• Enable/disable: Control overlay activation
• Priority adjustment: Modify overlay priority
• Cleanup: Remove unused overlays
• Backup: Backup overlay contents

Overlay Persistence

Persistence Strategies

1. Persistent Overlays

   • Survive system reboots
   • Stored in persistent storage
   • Maintain user customizations
   • Support long-term modifications

2. Temporary Overlays

   • Lost on system reboot
   • Stored in temporary storage
   • Support runtime modifications
   • Enable testing and experimentation

3. Hybrid Overlays

   • Selective persistence
   • Configurable persistence rules
   • Automatic cleanup policies
   • Smart persistence management

Storage Management

Storage Locations:

• User overlays: /var/lib/apt-ostree/overlays/user/
• System overlays: /var/lib/apt-ostree/overlays/system/
• Runtime overlays: /tmp/apt-ostree/overlays/
• Backup overlays: /var/lib/apt-ostree/overlays/backup/

Storage Optimization:

• Compression: Compress overlay data
• Deduplication: Remove duplicate content
• Cleanup: Automatic cleanup policies
• Archival: Archive old overlays

Runtime Modification System

Dynamic Configuration

Configuration Updates

File Modifications:

• Configuration files: Update service configs
• System files: Modify system settings
• User files: Update user preferences
• Temporary files: Create runtime files

Update Methods:

• Direct modification: Modify files directly
• Template application: Apply configuration templates
• Variable substitution: Substitute configuration variables
• Conditional updates: Apply updates conditionally

Service Management

Service Updates:

• Configuration reload: Reload service configuration
• Service restart: Restart modified services
• Dependency updates: Update service dependencies
• State preservation: Maintain service state

Update Coordination:

• Dependency ordering: Order updates by dependency
• Rolling updates: Update services incrementally
• Rollback support: Support update rollback
• Health monitoring: Monitor service health

State Management

Runtime State

State Components:

• Service state: Current service status
• Configuration state: Current configuration
• Package state: Installed package state
• System state: Overall system state

State Tracking:

• Change tracking: Track all changes
• State history: Maintain state history
• Rollback points: Create rollback points
• State validation: Validate state consistency

State Persistence

Persistence Methods:

• File-based: Store state in files
• Database: Store state in database
• Memory: Keep state in memory
• Hybrid: Combine multiple methods

State Synchronization:

• Real-time sync: Synchronize state in real-time
• Periodic sync: Synchronize state periodically
• Event-driven sync: Synchronize on events
• Manual sync: Manual synchronization

Security Considerations

Update Security

Update Validation

Security Checks:

• Package signatures: Verify package authenticity
• Source validation: Validate update sources
• Integrity checking: Check update integrity
• Compatibility verification: Verify update compatibility

Update Policies:

• Update approval: Require update approval
• Rollback policies: Define rollback policies
• Security scanning: Scan updates for security issues
• Update testing: Test updates before application

Access Control

Permission Management:

• Update permissions: Control who can apply updates
• Overlay permissions: Control overlay access
• Service permissions: Control service modifications
• Configuration permissions: Control configuration changes

Audit Logging:

• Update logging: Log all update operations
• Change tracking: Track all system changes
• Access logging: Log access to sensitive operations
• Security events: Log security-related events

Runtime Security

Overlay Security

Overlay Protection:

• Access control: Control overlay access
• Content validation: Validate overlay content
• Malware scanning: Scan overlay content
• Isolation: Isolate overlay operations

Security Policies:

• Content policies: Define allowed content
• Access policies: Define access rules
• Modification policies: Define modification rules
• Cleanup policies: Define cleanup rules

Performance Optimization

Update Performance

Update Optimization

Parallel Processing:

• Concurrent updates: Update multiple components concurrently
• Parallel downloads: Download updates in parallel
• Parallel installation: Install updates in parallel
• Parallel verification: Verify updates in parallel

Caching Strategy:

• Update caching: Cache update data
• Configuration caching: Cache configuration data
• Service caching: Cache service information
• State caching: Cache system state

Resource Management

Resource Optimization:

• Memory usage: Optimize memory usage
• Disk usage: Optimize disk usage
• CPU usage: Optimize CPU usage
• Network usage: Optimize network usage

Resource Limits:

• Memory limits: Set memory usage limits
• Disk limits: Set disk usage limits
• CPU limits: Set CPU usage limits
• Network limits: Set network usage limits

Overlay Performance

Overlay Optimization

Storage Optimization:

• Compression: Compress overlay data
• Deduplication: Remove duplicate content
• Efficient storage: Use efficient storage formats
• Cleanup policies: Implement cleanup policies

Access Optimization:

• Caching: Cache overlay data
• Indexing: Index overlay contents
• Lazy loading: Load overlay data on demand
• Prefetching: Prefetch frequently accessed data

Error Handling

Update Errors

Common Update Issues

1. Package Conflicts

   • Dependency conflicts
   • Version conflicts
   • Architecture conflicts
   • Repository conflicts

2. Service Issues

   • Service failures
   • Configuration errors
   • Dependency problems
   • State inconsistencies

3. System Issues

   • Disk space problems
   • Permission errors
   • Network issues
   • Resource exhaustion

Error Recovery

Recovery Strategies:

• Automatic rollback: Rollback failed updates
• Partial recovery: Recover partial updates
• Error reporting: Report detailed error information
• Recovery guidance: Provide recovery guidance

Rollback Mechanisms:

• Immediate rollback: Rollback immediately on failure
• Deferred rollback: Rollback after user confirmation
• Selective rollback: Rollback specific components
• Full rollback: Rollback entire update

Overlay Errors

Overlay Issues

1. Storage Problems

   • Disk space issues
   • Permission problems
   • Corruption issues
   • Access problems

2. Content Issues

   • Invalid content
   • Malicious content
   • Corrupted content
   • Incompatible content

3. System Issues

   • Mount failures
   • Union mount problems
   • Performance issues
   • Stability problems

Overlay Recovery

Recovery Methods:

• Content validation: Validate overlay content
• Corruption repair: Repair corrupted overlays
• Access restoration: Restore overlay access
• Performance optimization: Optimize overlay performance

Integration Points

System Integration

OSTree Integration

Live updates integrate with OSTree:

• Deployment management: Manage OSTree deployments
• Commit tracking: Track OSTree commits
• Rollback support: Support OSTree rollbacks
• Metadata management: Manage OSTree metadata

Service Integration

Integration with system services:

• systemd: Manage systemd services
• Service management: Control service lifecycle
• Configuration management: Manage service configuration
• State management: Track service state

User Interface Integration

CLI Integration

Command-line interface integration:

• Command execution: Execute live update commands
• Progress reporting: Report update progress
• Status display: Display update status
• Error reporting: Report update errors

DBus Integration

DBus interface integration:

• Update signals: Signal update events
• Progress signals: Signal progress updates
• Status signals: Signal status changes
• Error signals: Signal error conditions

Future Enhancements

Planned Features

1. Advanced Live Updates

   • Incremental updates
   • Delta updates
   • Smart update scheduling
   • Update prediction

2. Enhanced Overlays

   • Overlay templates
   • Overlay inheritance
   • Overlay validation rules
   • Overlay optimization

3. Performance Improvements

   • Update acceleration
   • Overlay optimization
   • Resource optimization
   • Caching improvements

4. Security Enhancements

   • Enhanced validation
   • Security scanning
   • Access control improvements
   • Audit enhancements

Implementation Notes

Current Status

• Basic live update functionality implemented
• User overlay system operational
• Runtime modification support
• Update coordination working

Next Steps

1. Advanced Features

   • Enhanced update system
   • Advanced overlay management
   • Performance optimization
   • Security improvements

2. Integration Improvements

   • Enhanced system integration
   • Better service management
   • Improved error handling
   • Enhanced user experience

3. Testing and Validation

   • Comprehensive testing
   • Performance testing
   • Security testing
   • Integration testing