Complete macOS hdiutil Command Guide: Disk Image Management, HTTP and SMB Mounting

Introduction to hdiutil

The hdiutil command is one of macOS’s most powerful disk image manipulation tools, providing comprehensive functionality for managing disk images, mounting remote volumes, and performing advanced disk operations. With macOS 15.5 Sequoia, hdiutil continues to be an essential tool for system administrators, developers, and power users who need precise control over disk image operations from the command line.

This comprehensive guide covers everything from basic DMG mounting to advanced HTTP and SMB network mounting operations, making it your complete reference for hdiutil mastery.

Understanding hdiutil Fundamentals

The hdiutil utility uses the DiskImages framework to manipulate disk images and provides functionality that goes far beyond simple mounting and unmounting. Key concepts include:

Attach vs Mount: Attaching connects the disk image to the system, while mounting makes the filesystem accessible
UDIF Format: Universal Disk Image Format is macOS’s native disk image format
Verification: Built-in checksum verification ensures image integrity
Network Support: Direct HTTP and SMB mounting capabilities

Basic hdiutil Syntax and Common Verbs

The basic syntax for hdiutil follows this pattern:

hdiutil verb [options] arguments

Essential verbs include:

attach – Mount disk images
detach – Unmount disk images
create – Create new disk images
convert – Convert between image formats
verify – Verify image integrity
info – Display information about attached images
burn – Burn images to optical media

DMG File Operations

Mounting DMG Files

The most common hdiutil operation is mounting DMG files. Here are various methods:

# Basic DMG mounting
hdiutil attach /path/to/image.dmg

# Mount without opening Finder window
hdiutil attach -noautoopen /path/to/image.dmg

# Mount with verbose output
hdiutil attach -verbose /path/to/image.dmg

# Mount without verification (faster but less secure)
hdiutil attach -noverify /path/to/image.dmg

Unmounting DMG Files

Several methods exist for unmounting disk images:

# Unmount by device name
hdiutil detach /dev/disk2

# Unmount by volume path
hdiutil detach "/Volumes/Volume Name"

# Force unmount (use with caution)
hdiutil detach -force /dev/disk2

Getting Information About Mounted Images

Use these commands to retrieve information about currently mounted images:

# List all mounted disk images
hdiutil info

# Get detailed information about specific image
hdiutil info -plist

HTTP Mounting with hdiutil

One of hdiutil’s powerful features is the ability to mount disk images directly from HTTP URLs, enabling remote access to disk images without downloading them first.

Basic HTTP Mounting

# Mount disk image from HTTP URL
hdiutil attach http://example.com/path/to/image.dmg

# Mount with authentication
hdiutil attach http://username:[email protected]/image.dmg

# Mount with specific user agent
hdiutil attach -useragent "CustomUserAgent/1.0" http://example.com/image.dmg

HTTPS Mounting with SSL Options

For secure HTTP connections, additional options are available:

# Mount from HTTPS with certificate verification
hdiutil attach https://secure.example.com/image.dmg

# Skip SSL verification (not recommended for production)
hdiutil attach -insecurehttp https://example.com/image.dmg

HTTP Mounting Best Practices

Always verify SSL certificates when possible
Use authentication credentials securely
Consider network bandwidth limitations
Implement timeout handling for large images

SMB Network Mounting

hdiutil can also mount disk images from SMB shares, providing seamless integration with network storage systems.

SMB Mounting Syntax

# Mount DMG from SMB share
hdiutil attach smb://server.local/share/image.dmg

# Mount with credentials
hdiutil attach smb://username:[email protected]/share/image.dmg

# Mount from Windows share
hdiutil attach smb://windows-server/SharedFolder/image.dmg

Advanced SMB Options

For enterprise environments, additional SMB options are available:

# Mount with specific SMB protocol version
hdiutil attach -smbprotocol SMB2 smb://server/share/image.dmg

# Mount with domain authentication
hdiutil attach smb://DOMAIN\\username:password@server/share/image.dmg

Creating and Converting Disk Images

Creating New Disk Images

hdiutil provides extensive options for creating disk images:

# Create blank disk image
hdiutil create -size 100m -fs HFS+ -volname "MyVolume" blank.dmg

# Create image from folder
hdiutil create -srcfolder /path/to/folder -format UDZO folder.dmg

# Create encrypted disk image
hdiutil create -size 100m -encryption AES-256 -stdinpass secure.dmg

Converting Image Formats

Convert between different image formats as needed:

# Convert DMG to ISO
hdiutil convert input.dmg -format UDTO -o output.iso

# Convert ISO to DMG
hdiutil convert input.iso -format UDZO -o output.dmg

# Convert to compressed format
hdiutil convert input.dmg -format UDZO -o compressed.dmg

Advanced hdiutil Operations

Verification and Integrity Checking

Ensure disk image integrity with verification commands:

# Verify disk image
hdiutil verify image.dmg

# Verify with verbose output
hdiutil verify -verbose image.dmg

# Check image information
hdiutil imageinfo image.dmg

Resizing Disk Images

Modify disk image sizes dynamically:

# Resize to specific size
hdiutil resize -size 200m image.dmg

# Resize to minimum possible size
hdiutil resize -sectors min image.dmg

Partition Operations

Work with partitioned disk images:

# Display partition map
hdiutil pmap image.dmg

# Attach specific partition
hdiutil attach -section 2 image.dmg

Security and Encryption Features

Working with Encrypted Images

Handle encrypted disk images securely:

# Mount encrypted image with password prompt
hdiutil attach encrypted.dmg

# Mount encrypted image with password from stdin
echo "password" | hdiutil attach -stdinpass encrypted.dmg

# Check if image is encrypted
hdiutil isencrypted image.dmg

Changing Passwords

Modify encryption passwords on existing images:

# Change password
hdiutil chpass image.dmg

# Change password non-interactively
hdiutil chpass -oldstdinpass -newstdinpass image.dmg

Performance Optimization and Best Practices

Optimization Flags

Use these flags to optimize performance:

# Disable automatic verification for speed
hdiutil attach -noverify image.dmg

# Quiet mode for scripting
hdiutil attach -quiet image.dmg

# Mount without mounting contained volumes
hdiutil attach -nomount image.dmg

Scripting Best Practices

When using hdiutil in scripts, consider these practices:

Always check return codes for error handling
Use absolute paths to avoid ambiguity
Implement proper cleanup for mounted images
Consider using plist output for parsing

Troubleshooting Common Issues

Mount Failures

Common solutions for mount failures:

# Force mount with specific filesystem
hdiutil attach -fsargs -o force image.dmg

# Mount with owners disabled
hdiutil attach -owners off image.dmg

# Mount with specific device node
hdiutil attach -drivekey system-image=true image.dmg

Network Mount Issues

Troubleshooting network mounts:

Verify network connectivity and permissions
Check firewall settings for SMB and HTTP traffic
Validate URL formatting and authentication credentials
Consider DNS resolution issues

Permission Problems

Resolve permission-related issues:

# Mount with specific user permissions
hdiutil attach -owners on image.dmg

# Mount with nobrowse to hide from Finder
hdiutil attach -nobrowse image.dmg

macOS 15.5 Sequoia Updates

macOS 15.5 Sequoia includes several improvements to hdiutil:

Enhanced APFS support for modern disk operations
Improved security validation for network mounts
Better integration with System Integrity Protection
Enhanced performance for large disk image operations
Updated encryption algorithms for better security

Integration with Other macOS Tools

Working with diskutil

Combine hdiutil with diskutil for comprehensive disk management:

# Mount image and get disk identifier
DISK=$(hdiutil attach -nomount image.dmg | head -1 | awk '{print $1}')

# Use diskutil to mount filesystem
diskutil mount $DISK

Automation Scripts

Create automated workflows combining multiple tools:

#!/bin/bash
# Automated image mounting script
IMAGE_URL="http://example.com/software.dmg"
MOUNT_POINT="/tmp/mounted_image"

# Mount image
hdiutil attach "$IMAGE_URL" -nobrowse -mountpoint "$MOUNT_POINT"

# Perform operations
cp "$MOUNT_POINT/Application.app" /Applications/

# Cleanup
hdiutil detach "$MOUNT_POINT"

Conclusion

The hdiutil command is an indispensable tool for macOS users who need comprehensive disk image management capabilities. From basic DMG mounting to advanced HTTP and SMB network operations, hdiutil provides the flexibility and power needed for both simple tasks and complex automation workflows.

Whether you’re a system administrator managing enterprise deployments, a developer working with disk image distributions, or a power user seeking greater control over your macOS system, mastering hdiutil will significantly enhance your command-line capabilities.

Remember to always verify image integrity when security is important, use appropriate authentication methods for network mounts, and implement proper error handling in automated scripts. With the knowledge from this guide, you’re well-equipped to leverage hdiutil’s full potential in macOS 15.5 Sequoia and beyond.