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Install dmg2img via your package manager (e.g., sudo apt install dmg2img ). Convert the DMG file to an ISO image: dmg2img /path/to/installer.dmg /path/to/installer.iso Use code with caution.
Select the root name of your USB drive from the left sidebar. Click the button in the top toolbar. Configure the erasure settings as follows:
Open (Press Command + Space , type "Disk Utility", and press Enter ).
Example for macOS Monterey:
Open the mounted volume. Look for an application named (e.g., Install OS X El Capitan.app ). Drag this .app bundle into your Mac's Applications folder. Unmount (Eject) the DMG file once the copy is complete. Step 2: Format the USB Drive Plug your USB flash drive into the Mac. Open Disk Utility (Navigate to Applications > Utilities ).
Open (Press Cmd + Space , type "Disk Utility", and hit Enter).
Click . Disk Utility will block-copy the contents of the disk image directly onto the USB drive, rendering it bootable for older Mac architectures. Method 3: Creating the Bootable USB from Windows
Drag this .app file into your Mac’s folder. This step is vital for the Terminal command to locate the source files. Step 2: Format the USB Drive
Double-click your macOS DMG file to mount it as a virtual disk on your desktop.
: Ensure it is compatible with your target Mac model. Backup : The process will erase all data on the USB drive. Option 1: On a Mac (Official Method)
Creating a bootable macOS USB installer directly from a DMG file can be challenging. Apple’s official documentation only covers creating installers using the .app file downloaded from the Mac App Store. However, if you only have a DMG file—often the case for older OS X versions like Lion, Mountain Lion, Yosemite, or El Capitan—you can still create a functional bootable drive.
: Use Disk Utility to erase your USB drive (at least 16GB) as Mac OS Extended (Journaled) with a GUID Partition Map .
If you are trying to create an older installer on a brand new Mac running a modern OS (like macOS Sonoma or Sequoia), the system security configuration may prevent execution of the utility. You may need to use an older Mac model to run the createinstallmedia command successfully.
Flush and eject: