Open Terminal (Applications → Utilities → Terminal) and run:
ls /Applications/ | grep "Install"
You should see something like Install macOS Sonoma.app or Install macOS Monterey.app.
Note the exact name – you'll need it for the next step.
In Terminal, use the following template:
sudo /Applications/Install\ macOS\ [Version].app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Examples:
Note: For very old OS X installers (e.g., Lion, Mountain Lion), you may need to use a different method or restore the
.dmgdirectly via Disk Utility's Restore feature.
This method uses dd or asr (Apple Software Restore) to write the DMG directly to the USB drive.
Warning: This only works if the DMG is a bootable disk image (contains a full file system with bootloader). Most modern macOS installer DMGs are not bootable in this raw form.
Steps:
Limitation: This rarely produces a bootable installer for modern Macs because Apple’s firmware expects a specific partition layout and bootloader structure that dd does not recreate from a loose DMG.
Before we begin, it is crucial to understand what a DMG file is. A DMG (Apple Disk Image) is a container format that can hold anything: an application, a folder of files, or a bootable disk image.
Our goal is to take that DMG and write it to a USB drive so that your Mac can recognize it as a startup disk.
By following these steps, you'll have a bootable macOS installer on a USB drive, ready for installation on your or another Mac. create mac os x bootable usb installer from dmg
Creating a bootable macOS installer from a DMG file is a critical task for system recovery, clean installations, or reviving older hardware. Depending on whether you are working from a Windows PC or a functional Mac, the process varies significantly between using professional flashing utilities or native command-line tools. 1. Creating the Installer on a Windows PC
When your Mac is unbootable, Windows becomes the primary platform for creating recovery media. Because Windows cannot natively write to Mac-formatted file systems (HFS+), specialized software is required. Tool of Choice: TransMac
is the industry standard for this task. It allows Windows users to open Mac-formatted drives and "restore" DMG images directly to a USB stick. Preparation via Diskpart Before flashing, you must ensure the USB drive uses the GPT (GUID Partition Table)
scheme, as modern Macs will not boot from the older MBR format. Open Command Prompt as Administrator and type select disk X (where X is your USB). followed by convert gpt Create a primary partition with create partition primary The Flashing Process Open TransMac as an Administrator . Right-click your USB drive and select Format Disk for Mac . Once formatted, right-click again and choose Restore with Disk Image , then select your downloaded macOS DMG file. Super User 2. Creating the Installer on macOS Open Terminal (Applications → Utilities → Terminal) and
On a working Mac, the process is safer and more reliable because you can use Apple's native createinstallmedia Create a bootable installer for macOS - Apple Support
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume. Catalina. sudo / Apple Support Create a macOS Bootable USB on Windows PC [from DMG File]