To create a bootable Mac drive you need any disk with Mac OS X 10.11.0 El Capitan or newer (10.12 Sierra, 10.13 High Sierra, 10.14 Mojave, 10.15 Catalina) either running as your main system, or just being installed on a drive that's connected to your Mac at the moment. Download and keep a copy of the ‘Install OS X El Capitan’ App. (Download from App store but make a copy of it before you install it as the Apple Installer deletes it after you use it.) Put it in your ‘Applications’ folder. Format your blank USB (8GB is a good size) as Apple OS X Extended (Journaled) using Disk Utility and call it.
Introduction
Apple officially released OS X 10.11 El Capitan operating system in September 2015 as an update through Apple App Store. This actualization will update core of your system and preserve your user data.
However, if you want to have a clean installation of El Capitan on your Mac you will need to create a special installation USB drive and in this article we will show you how.
Four ways how to create El Capitan USB installation flash drive:
Preparation - get OS X El Capitan installer and USB flash drive
Download El Capitan installer (Install OS X El Capitan.app in Applications folder) available in Mac App Store.
Prepare a flash drive with OS X Disk Utility. Format it with GUID Partition Table and name it as Untitled. The minimal capacity of flash drive must be 8 GB.
How to create El Capitan installation USB drive with createinstallmedia tool
The createinstallmedia is a command line tool distributed with OS X installer.
When you have prepared your USB flash drive and El Capitan installer is downloaded from App Store ► open Terminal and type command:
sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install OS X El Capitan.app --nointeraction
In our case 'Untitled' is the name of USB flash drive! Replace 'Untilled' by name of your flash drive.
Wait a few minutes and your El Capitan installation USB drive will be prepared.
To install OS X El Capitan ► restart computer ► hold the Option key and select Installation USB drive from the menu.
How to create El Capitan USB installation with Terminal commands
When your USB flash drive is ready and El Capitan installer downloaded from App Store ► Open Terminal and type the following sequence of commands:
sudo hdiutil attach /Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg
sudo asr restore -source /Volumes/OS X Install ESD/BaseSystem.dmg -target /Volumes/Untitled -erase -format HFS+
sudo rm /Volumes/OS X Base System/System/Installation/Packages
sudo cp -a /Volumes/OS X Install ESD/Packages /Volumes/OS X Base System/System/Installation/Packages
sudo cp -a /Volumes/OS X Install ESD/BaseSystem.chunklist /Volumes/OS X Base System
sudo cp -a /Volumes/OS X Install ESD/BaseSystem.chunklist /Volumes/OS X Base System
sudo cp -a /Volumes/OS X Install ESD/BaseSystem.dmg /Volumes/OS X Base System
hdiutil detach /Volumes/OS X Install ESD
Now wait until your bootable installation flash drive with OS X 10.11 El Capitan is made.
To install OS X El Capitan ► restart computer ► hold the Option key and select Installation USB drive from the menu.
How to create El Capitan USB installation with Disk Utility and Finder
When your USB flash drive is ready and El Capitan installer downloaded from App Store ► Open Terminal and type:
defaults write com.apple.finder AppleShowAllFiles 1 && killall Finder
This command allows you to view hidden files in Finder.
Now Open Finder ► Applications ► Install OS X El Capitan.app ► right click ► Select Show Package Contents option.
Navigate to Contents/SharedSupport ► Mount InstallESD.dmg file
Open OS X Install ESD archive in Finder and mount BaseSystem.dmg archive
Connect USB drive and open Disk Utility (/Applications/Utilities)
Select the USB drive from the list of disks, select Restore tab and pick Select OS X Base System archive as a source and USB flash drive as the destination. When ready click on Restore button.
After the Restore process is finished, open Finder ► open USB drive (OS X Base System) ► go to the System/Installation folder and select Packages file and delete it.
Open OS X Install ESD volume in Finder, select Packages folder and copy them to System/Installation folder on USB drive.
Also copy BaseSystem.chunklist and BaseSystem.dmg files from InstallESD.dmg volume to root of USB flash drive (OS X Base System).
Now your El Capitan installation USB drive is prepared and ready for use.
To install OS X El Capitan ► restart computer ► hold the Option key and select Installation USB drive from the menu.
How to create El Capitan USB installation disk with DiskMaker X
DiskMaker X tool is Wizard like tool that allows you create OS X installation disk. Download DiskMaker X to your Mac and copy it to Applications folder.
When you have prepared your USB flash drive and El Capitan installer is downloaded from App Store ► open DiskMaker X.
Select version of OS X (in our case El Capitan)
Select copy of OS X installation app
Select USB drive that will be used for USB installation
Create El Capitan Usb Installer
And wait a few minutes till the the DiskMaker X finish creating process.
El Capitan Usb Boot
To install OS X El Capitan ► restart computer ► hold the Option key and select Installation USB drive from the menu.