vfs-verifier

Virtual File System Data Verifier

Overview

vfs-verifier validates and analyzes data recovered from Domesday LaserDiscs and other VFS-containing optical media. It verifies file system integrity, extracts metadata, and provides detailed analysis of data recovery quality and completeness.

Usage

vfs-verifier [options] <input.bin> [output_report.txt]

Options

• -h, --help - Display help information
• -v, --version - Display version information
• -d, --debug - Show debug output
• -q, --quiet - Suppress info and warning messages
• --vfs-type TYPE - Specify VFS type (domesday, acorn, generic)
• --output-metadata FILE - Generate detailed metadata report
• --verify-checksums - Perform checksum verification where available
• --extract-files - Extract individual files from the VFS
• --output-dir DIR - Directory for extracted files (default: vfs_extracted)
• --summary-only - Generate summary report only

Arguments

• input.bin - Input binary data file from efm-decoder-data
• output_report.txt - Optional output verification report

VFS Type Support

Domesday LaserDisc VFS

• Purpose: BBC Domesday Project data verification
• Structure: Acorn DFS with custom extensions
• Features: Geographic data, text, images, software
• Validation: CRC checks, file table verification, geographic data integrity

Acorn DFS

• Purpose: General Acorn Disk Filing System verification
• Structure: Standard Acorn DFS layout
• Features: File allocation, directory structures
• Validation: Catalog integrity, file size verification

Generic VFS

• Purpose: Unknown or custom file systems
• Structure: Basic structural analysis
• Features: Pattern recognition, data classification
• Validation: Structural consistency checks

Verification Process

File System Analysis

1. Header Validation: Check VFS header and magic numbers
2. Directory Structure: Verify directory entries and allocation
3. File Table: Validate file allocation table consistency
4. Cross-References: Check file size vs. allocated sectors
5. Metadata: Extract and verify embedded metadata

Data Integrity Checks

• Checksums: Verify embedded checksums where available
• Consistency: Cross-check redundant information
• Completeness: Identify missing or corrupted sectors
• Geographic Data: Validate coordinate systems and data ranges (Domesday)

Pipeline Integration

Input Requirements

• Binary data file from efm-decoder-data
• Preferably error-corrected and verified data
• Complete file system image (partial images supported but limited)

Standard Workflow

Domesday Data Recovery

# Complete pipeline from EFM to verified VFS
efm-decoder-f2 domesday.efm domesday.f2
efm-decoder-d24 domesday.f2 domesday.d24
efm-decoder-data domesday.d24 domesday.bin --output-metadata domesday_meta.txt

# Verify and extract VFS
vfs-verifier domesday.bin domesday_report.txt \
  --vfs-type domesday \
  --verify-checksums \
  --extract-files \
  --output-dir domesday_extracted \
  --output-metadata domesday_vfs_meta.txt

Quality Assessment Workflow

# Multi-source stacked recovery with verification
efm-stacker-f2 dom1.f2 dom2.f2 dom3.f2 stacked.f2
efm-decoder-d24 stacked.f2 stacked.d24 
efm-decoder-data stacked.d24 final.bin

# Comprehensive verification
vfs-verifier final.bin quality_report.txt \
  --vfs-type domesday \
  --verify-checksums \
  --debug \
  --output-metadata complete_analysis.txt

Output Reports

Summary Report

Basic verification results:

• VFS type identification
• Total files found/expected
• File system integrity status
• Overall data recovery percentage
• Critical errors and warnings

Detailed Metadata Report

Comprehensive analysis including:

• Complete file listing with sizes and checksums
• Directory structure map
• Sector allocation analysis
• Geographic coordinate verification (Domesday)
• Data classification and content analysis
• Corruption pattern analysis

Extracted Files

When --extract-files is used:

• Individual files extracted to specified directory
• Original file names and metadata preserved
• Corrupted files marked with .partial extension
• Index file listing all extractions

Quality Metrics

File System Level

• Completeness: Percentage of expected files successfully recovered
• Integrity: File system structure consistency
• Accessibility: Files that can be fully extracted vs. partially recovered

Data Level

• Checksum Verification: Files passing embedded checksum tests
• Geographic Accuracy: Coordinate system validation (Domesday specific)
• Content Classification: Data type identification and validation

Error Detection and Reporting

File System Errors

• Missing or corrupted directory entries
• Invalid file allocation table entries
• Inconsistent file sizes
• Broken cross-references

Data Corruption Patterns

• Systematic vs. random errors
• Sector-level corruption clustering
• EFM-to-data error propagation analysis
• Recovery success correlation with input quality

Technical Details

VFS Structure Analysis

• Sector Size: Typically 1024 bytes (Domesday), 256 bytes (Acorn DFS)
• Directory Format: Acorn DFS catalog format with extensions
• File Allocation: Track allocation table consistency
• Metadata: Extract creation dates, file attributes, checksums

Domesday-Specific Features

• Geographic Data: Validate OS Grid References and coordinate systems
• Image Data: Verify embedded image formats and compression
• Text Data: Check character encoding and text structure
• Software: Validate executable file integrity

Integration with Other Tools

Error Correction Pipeline

vfs-verifier provides feedback for:

• efm-decoder-data parameter tuning
• Multi-source stacking quality assessment
• Optimal recovery strategy selection

Archive Workflows

Results can be used for:

• Digital preservation documentation
• Research data validation
• Historical accuracy verification
• Long-term storage planning