Creating a bootable macOS USB installer from a file is a multi-step process that varies depending on whether you are using a Mac or a Windows PC. If you are starting with a DMG file downloaded from Apple (like El Capitan or Yosemite), you must first extract the actual installer application before you can create the bootable drive. Apple Support Community Method 1: On macOS (Recommended) Apple's official method uses a command-line tool called createinstallmedia Extract the Installer : Double-click the file to mount it. Inside, you will usually find a
| Issue | Solution |
|--------|----------|
| Command not found | Check the .app name and path carefully – use Tab key for autocomplete |
| "MyVolume" not found | Rename USB to exactly MyVolume (case-sensitive) or adjust the command |
| DMG contains only a .pkg | Install the .pkg first, which places the .app into Applications |
| .app is hidden in the DMG | Some DMGs have InstallESD.dmg – mount it and use Disk Utility's Restore feature instead |
| Old macOS (Lion/Mountain Lion) | Use Disk Utility: drag InstallESD.dmg → select USB → click Restore |
Format the Drive: Use Disk Utility to erase the USB drive. Set the format to Mac OS Extended (Journaled) and the scheme to GUID Partition Map. create mac os x bootable usb installer from dmg
The process takes 10–30 minutes.
If you do not have access to a Mac, you can use third-party software like Creating a bootable macOS USB installer from a
Open Terminal (Applications → Utilities → Terminal) and run:
Convert the .dmg to a raw image if needed (only if the dmg is in HFS+ or APFS hybrid that dd can't write directly): Inside, you will usually find a Troubleshooting Tips
Steps: