Simple script to generate container images. You can configure the total size and number of layers. The script generates a Dockerfile along with bin files, which can be then used to build an image. Note that the unit used is GB and not GiB.

generate_container_image.sh

#!/bin/bash
# Usage: ./generate_strict_gb.sh <TOTAL_GB_SI> <LAYER_COUNT> <OUTPUT_DIR>

TOTAL_GB=$1
LAYERS=$2
OUT_DIR=$3

if [ -z "$OUT_DIR" ]; then
  echo "Usage: $0 <TOTAL_GB> <LAYERS> <OUTPUT_DIR>"
  echo "Note: Uses strict SI Gigabytes (1 GB = 1,000,000,000 bytes)"
  exit 1
fi

mkdir -p "$OUT_DIR"

# Use scratch for zero overhead
cat <<EOF > "$OUT_DIR/Dockerfile"
FROM scratch
EOF

# Total bytes per layer
BYTES_PER_LAYER=$(python3 -c "print(int(($TOTAL_GB * 1000000000) / $LAYERS))")
MB_DISPLAY=$(python3 -c "print(round($BYTES_PER_LAYER / 1000000, 2))")

# Chunk size configuration (safe limit - 500MB per write)
SAFE_CHUNK_SIZE=500000000

echo "----------------------------------------------------------------"
echo "Target: ${TOTAL_GB} GB (SI) | Layers: ${LAYERS}"
echo "Per Layer: ${BYTES_PER_LAYER} bytes (~${MB_DISPLAY} MB)"
echo "Base Image: scratch (0 bytes overhead)"
echo "----------------------------------------------------------------"

for i in $(seq 1 $LAYERS); do
    FILENAME="layer_${i}.bin"
    FILEPATH="$OUT_DIR/$FILENAME"
    
    echo -ne "Generating $FILENAME ... "
    
    # Reset/Create empty file
    : > "$FILEPATH"
    
    CURRENT_SIZE=0
    REMAINING=$BYTES_PER_LAYER
    
    # Append chunks until layer is full
    while [ $REMAINING -gt 0 ]; do
        if [ $REMAINING -ge $SAFE_CHUNK_SIZE ]; then
            NEXT_CHUNK=$SAFE_CHUNK_SIZE
        else
            NEXT_CHUNK=$REMAINING
        fi
        
        # Append random data to the file
        openssl rand $NEXT_CHUNK >> "$FILEPATH"
        
        REMAINING=$((REMAINING - NEXT_CHUNK))
    done
    
    echo "Done."
    
    # Copy to root since we have no WORKDIR
    echo "COPY $FILENAME /$FILENAME" >> "$OUT_DIR/Dockerfile"
done

echo -e "\n✅ Context generated in: $OUT_DIR"