How to Fix macOS DMG Build Errors — Disk Image Creation

In this tutorial, you'll learn about How to Fix macOS DMG Build Errors. We cover key concepts, practical examples, and best practices.

The Problem

Creating a DMG fails:

hdiutil: create failed - error 5341

or:

The DMG is too small for the contents.

Quick Fix

Step 1: Create a DMG from a folder

hdiutil create -volname "MyApp" -srcfolder /path/to/MyApp.app   -ov -format UDZO MyApp.dmg

Step 2: Create a DMG with custom layout

# Create a temporary disk image:
hdiutil create -size 100m -fs HFS+ -volname "MyApp" -ov MyAppTemp.dmg

# Mount it:
hdiutil attach MyAppTemp.dmg

# Copy the app:
cp -R /path/to/MyApp.app /Volumes/MyApp/

# Create alias to Applications folder:
ln -s /Applications /Volumes/MyApp/Applications

# Detach:
hdiutil detach /Volumes/MyApp

# Convert to compressed:
hdiutil convert MyAppTemp.dmg -format UDZO -o MyApp.dmg

Step 3: Fix size issues

# Calculate the correct size:
du -sh /path/to/MyApp.app
# Add 20% overhead

hdiutil create -size 120m -fs HFS+ -volname "MyApp" MyAppTemp.dmg

Step 4: Add background image

# After mounting the temp DMG:
mkdir /Volumes/MyApp/.background
cp background.png /Volumes/MyApp/.background/

# Use AppleScript to set background (or use a DMG creation tool)

Step 5: Sign the DMG

codesign --force --deep --sign "Developer ID Application: Name (TEAMID)" MyApp.dmg

Step 6: Convert to read-only

hdiutil convert MyAppRW.dmg -format UDZO -o MyApp.dmg

Prevention

• Always estimate DMG size as source size + 20% overhead.
• Use a clean build output for the DMG source.
• Sign the DMG after creation for distribution.

Common Mistakes with dmg build

1. Using return to exit a function early instead of wrapping a pure value in the monad
2. Mixing let bindings with <- bindings in do notation, producing type errors
3. Overlapping type class instances that cause GHC to reject the program with ambiguous dispatch errors

These mistakes appear frequently in real-world MACOS code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ