qcow2 Compression

compress.bash

#!/usr/bin/bash

# Function to get file size in human-readable format
get_size() {
    du -h "$1" | cut -f1
}

# Function to get file size in bytes for calculation
get_size_bytes() {
    stat -c %s "$1" 2>/dev/null || stat -f %z "$1" 2>/dev/null
}

# Check if filename provided
if [ $# -eq 0 ]; then
    echo "Usage: $0 <filename>"
    echo "Example: $0 mydisk"
    exit 1
fi

# Validate input (no path traversal, no special chars)
filename="$1"
if [[ "$filename" =~ [^a-zA-Z0-9_.-] ]]; then
    echo "Error: Filename contains invalid characters"
    exit 1
fi

# Check if source exists
source_file="${filename}.qcow2"
if [ ! -f "$source_file" ]; then
    echo "Error: Source file '$source_file' not found"
    exit 1
fi

# Display initial info
echo "=========================================="
echo "Processing: $source_file"
echo "=========================================="

# Get original size
original_size=$(get_size "$source_file")
original_bytes=$(get_size_bytes "$source_file")
echo "Original size: $original_size"

# Create backup with timing
backup_file="${filename}_backup.qcow2"
echo ""
echo "[1/2] Creating backup..."

backup_start=$(date +%s.%N)
cp "$source_file" "$backup_file"
backup_status=$?
backup_end=$(date +%s.%N)

if [ $backup_status -ne 0 ]; then
    echo "Error: Failed to create backup"
    exit 1
fi

backup_time=$(echo "$backup_end - $backup_start" | bc)
echo "  ✓ Backup created: $backup_file"
echo "  ⏱  Time: ${backup_time} seconds"

# Check if qemu-img is available
if ! command -v qemu-img &> /dev/null; then
    echo "Error: qemu-img not found"
    exit 1
fi

# Compress with timing
echo ""
echo "[2/2] Compressing with qemu-img (using -c flag)..."

compress_start=$(date +%s.%N)
qemu-img convert -O qcow2 -c "$backup_file" "$source_file"
compress_status=$?
compress_end=$(date +%s.%N)

if [ $compress_status -ne 0 ]; then
    echo "Error: Compression failed"
    exit 1
fi

compress_time=$(echo "$compress_end - $compress_start" | bc)

# Get compressed size
compressed_bytes=$(get_size_bytes "$source_file")
compressed_size=$(get_size "$source_file")

# Calculate size reduction
if [ $original_bytes -gt 0 ]; then
    reduction_bytes=$((original_bytes - compressed_bytes))
    reduction_percent=$(echo "scale=2; ($reduction_bytes * 100) / $original_bytes" | bc)

    # Convert reduction bytes to human readable
    if [ $reduction_bytes -gt 1073741824 ]; then
        reduction_hr=$(echo "scale=2; $reduction_bytes / 1073741824" | bc)"G"
    elif [ $reduction_bytes -gt 1048576 ]; then
        reduction_hr=$(echo "scale=2; $reduction_bytes / 1048576" | bc)"M"
    elif [ $reduction_bytes -gt 1024 ]; then
        reduction_hr=$(echo "scale=2; $reduction_bytes / 1024" | bc)"K"
    else
        reduction_hr="${reduction_bytes}B"
    fi
fi

# Display results
echo ""
echo "=========================================="
echo "COMPLETE! Summary:"
echo "=========================================="
echo "Original size:      $original_size"
echo "Compressed size:    $compressed_size"
echo "Space saved:        $reduction_hr ($reduction_percent%)"
echo ""
echo "Timing:"
echo "  Backup:           ${backup_time} seconds"
echo "  Compression:      ${compress_time} seconds"
echo "  Total time:       $(echo "$backup_time + $compress_time" | bc) seconds"
echo ""
echo "Files:"
echo "  Original (compressed): $source_file"
echo "  Backup (uncompressed): $backup_file"
echo "=========================================="

# Optional: Show compression ratio
if [ $original_bytes -gt 0 ]; then
    ratio=$(echo "scale=2; $compressed_bytes / $original_bytes" | bc)
    echo "Compression ratio:  ${ratio}:1"
    echo "=========================================="
fi