Fix macOS Catalina DMG Installation Errors: A Quick Guide

Updated at: 02/07/2025

Upgrading to macOS Catalina? Encountering DMG installation errors can be frustrating. This quick guide provides straightforward solutions to common problems preventing a smooth installation. We'll cover troubleshooting steps, from disk verification and permissions to addressing potential conflicts with existing software. Get back on track to enjoying the latest macOS features – let's fix those errors!

Step-by-Step Instructions

  1. Prepare for Installation

    • Check your internet connection and turn off Wi-Fi.
    Check your internet connection and turn off Wi-Fi.
    Prepare for Installation

  2. Initiate Installation

    • Open the DMG file and click "Show Package Contents". Navigate to the macOS folder and double-click the installer.
    • Enter your password when prompted.
    Enter your password when prompted. Enter your password when prompted.
    Initiate Installation

  3. Troubleshoot Installation Errors

    • If you encounter an error preventing installation, go to System Preferences > Security & Privacy.
    • Unlock the Security & Privacy settings using the lock icon. Allow the application to run from the specified location. Quit the installer.
    Unlock the Security & Privacy settings using the lock icon. Allow the application to run from the specified location. Quit the installer. Unlock the Security & Privacy settings using the lock icon. Allow the application to run from the specified location. Quit the installer.
    Troubleshoot Installation Errors

  4. Resume and Complete Installation

    • Reopen the installer.
    • The installation should now proceed successfully. Do not close the installer window during installation.
    The installation should now proceed successfully. Do not close the installer window during installation. The installation should now proceed successfully. Do not close the installer window during installation.
    Resume and Complete Installation
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Tips

  • Don't close the installer window during the installation process.
  • Keep your internet connection off until the installation is complete (though this is not explicitly stated in the video, it's a good practice).

Common Mistakes to Avoid

1. Insufficient Disk Space

Reason: The DMG file requires more free space than available on your startup disk.
Solution: Free up sufficient disk space by deleting unnecessary files or moving them to an external drive before reinstalling.

2. Corrupted DMG File

Reason: The downloaded DMG file may be damaged during download or transfer.
Solution: Download the DMG file again from a trusted source, verifying its integrity after the download is complete.

3. Permissions Issues

Reason: Insufficient permissions to write to the target disk or location.
Solution: Try installing the DMG as an administrator by running the installer application with elevated privileges.

FAQs

My macOS Catalina DMG file won't open. What should I do?
Try verifying the DMG file's integrity using Disk Utility. Look for errors and repair them if possible. If the problem persists, try downloading the DMG again from the official Apple website.
I get an error message saying 'The disk you inserted was not readable by this computer.' What's wrong?
This usually indicates a problem with the DMG file itself or your disk drive. Try downloading the DMG again. If the problem continues, check your disk drive for errors using Disk Utility and ensure it's properly connected.
After starting the installation, I get an error message. What should I try?
Restart your Mac in Safe Mode (hold Shift during startup). This disables non-essential startup items that might be causing conflicts. Then, try the installation again. If the problem persists, you might need to create a bootable installer using a USB drive.