This guide deals with 3 ways of making a boot disk from macOS, the first one is the fastest and is done via the Terminal from a command in macOS called createinstallmedia, the other 2 are older ways are done with a mixture of finder using Disk Utility and command line.

The first way can support macOS Big SurmacOS CatalinamacOS Mojave or macOS High Sierra and further back to SIerra, El Capitan, Yosemite and Mavericks.

Osx 109 Mavericks System Requirements

Quickest Way

Download the macOS version you need but don’t install.

Attach your USB stick/drive.

Launch the Terminal from /Applications/Utilities and enter the command below and then your password when prompted, be sure to change the ‘Untitled‘ name in the below command to your external disk name:

sudo /Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install OS X Mavericks.app --nointeraction
Mavericks Boot Image

Let it do its thing and there you have it, one bootable macOS drive.

This really is a super simple way – however if using the Terminal fills you with fear and dread, there are some GUI apps that can get the job done namely DiskMakerX and a new imaging tool that can clone a new disk very quickly – AutoDMG, although AutoDMG can not work with macOS Big Sur

Alternative Ways of building a Bootable macOS Disk.

An alternative way to make a boot disk of macOS (but not macOS Big Sur), first of all, get the app or download via the App store, if downloaded it will file in the folder  Applications.

The example below uses OSX Mavericks.

Maverick App Location

Control / Left click Options, Show in Finder to get to the app, don’t install at this stage.

Maverick Application Folder

Located in the Applications Folder

Finding the InstallESD.dmg

To find the actual InstallESD.dmg file, control/left click the ‘Install macOS’ app and choose show contents – then navigate to Shared Support folder.

Maverick App Show Contents

Control/Right click to show contents

Maverick App Installesd

Navigate to Shared Support folder to see the InstallESD.dmg file

Mount InstallESD.dmg

Double click to mount the image.

Make Invisible Files Visible

We need to see the BaseSystem.dmg inside the InstallESD.dmg

Crank open Terminal and run:

defaults write com.apple.Finder AppleShowAllFiles TRUE
 killall Finder

This will show all invisible files have a look inside the mounted InstallESD.dmg

Basechunklist

 Mount an External Disk

Attach a USB/external drive – this guide uses the external drive name called BootDisk, you need to make sure the format is correct, it needs to be Mac OSX Extended Journaled – if it’s not you can format that in Disk Utility.

Launch Disk Utility

Launch Disk Utility as found in Applications/Utilities and go to the Restore tab.

Basesystem Restore

Drag BaseSystem.dmg to the Source field and your external disk to the Destination and click Restore.

This will mount your new macOS external disk and name it OSX Base System – but we need to add the packages.

Fix the Packages

Couple of things to fix in the newly created boot disk, remove the Package alias at System/Installation/ folder

Remove Package Alias

Now from the previously mounted InstallESD.dmg copy over the Packages folder to the same location where we just removed the alias above.

Add Package Folder

Will take a while as it holds all the install packages.

Job done now you can boot from the OSX 10.9 disk.

Boot From Osx9

Make the Visible back to Invisible

If you want all to return back to normal and hide the system files run a couple more commands in the Terminal

defaults write com.apple.Finder AppleShowAllFiles FALSE
killall Finder

How to create the OSX 10.9 Mavericks Bootable Drive just via Terminal

Just for the crazy ones……after Mavericks is downloaded….and again this assumes you external disk is named BootDisk

Mount the InstallESD.dmg buried deep in the app

hdiutil attach /Applications/Install OS X Mavericks.app/Contents/SharedSupport/InstallESD.dmg -noverify

Swap to the newly mounted image

cd /Volumes/InstallESD.dmg

This puts you back in the Finder in front of the newly mounted InstallESD.dmg, go back to Terminal and clone the BaseSystem.dmg to the remote USB drive

sudo asr restore -source /Volumes/OS X Install ESD/BaseSystem.dmg -target /Volumes/BootDisk/ -erase -noverify

This will change ‘BootDisk‘ to ‘OS X  Base System

Remove the existing Packages alias link from the newly restored image

rm /Volumes/OS X Base System/System/Installation/Packages

Copy the full OSX Mavericks Packages over to the new image….takes a while

cp -R /Volumes/OS X Install ESD/Packages/ /Volumes/OS X Base System/System/Installation/Packages

And there it is! – to eject the new bootable USB OSX Mavericks 10.9 disk ‘cd’ to home and eject

cd ~/
hdiutil eject /Volumes/OS X Base System/

Now you can boot up from your newly bootable disk and either Install OSX10.9 on another device or use the Terminal/Disk Utility or Firmware Password Utilities on another device.

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