Create a macOS installation disc with createinstallmedia and install macOS on multiple Mac computers, perform a cleaan install, or access a failed Mac that won’t start.

In this article we are going to show you step by step how to create a bootable USB, Mac operating system installer, either to install the latest version of macOS on multiple Macs; install the latest beta version of macOS, perform a clean install, or repair a disk.

Many users choose this alternative of having a bootable disk or emergency bootable if it turns out that your Mac has startup problems and you cannot connect to the Internet or access the recovery mode.

If you want to know how to do a boot install of macOS Catalina, macOS Mojave or an earlier version of Mac OS X or macOS, you have come to the right place.

You can also use your bootable USB to install macOS on a separate hard drive volume (or on a partition if you are running an earlier version of Mac OS). It is an easy way to go back to a previous version of macOS.

The reasons why you may want to create this bootable USB may also be to avoid waiting for the installer download every time you want to use it on a different Mac. In this way, you will have it on your USB locally.

Fortunately, doing a bootable installation of the Mac operating system has become much easier over time, especially since Apple released OS X Mavericks in 2013.

Create Bootable macOS USB Installer Using UUByte App

UUByte DMG Editor is a cross-platform desktop app for creating bootable USB installer from various disk image files, including .dmg, .iso, .img, .bin, etc… If you already downloaded macOS DMG file, then this app is best option to create a bootable USB installer for macOS and OS X.

  1. Go to the product page (uubyte.com/dmg-editor.html) and download the setup file on your Mac.
  2. Mount the .dmg file and drag the app icon to Application folder so you can run this app directly from Launchpad.
  3. From the welcome screen, click ‘Burn’ tab. Now, you will be redirected to a new window.
  4. Insert a USB drive and add the macOS DMG file to the app via ‘Browse’ button.
  5. Click ‘Burn’ button at the bottom to start copying dmg file to USB drive. You should wait a couple of minutes to get it done.

This method is much easier than Terminal app, where you should type different commands to complete the task.

Create a boot installer for macOS use the command ‘Terminal createinstallmedia’

With that version of Mac OS X, and all later versions, it has been possible to use the command ‘Terminal createinstallmedia’ to create a boot installer for macOS. In this article we are going to show you how to do it step by step.

We will perform the following steps to create a bootable USB for Mac:

  1. Get macOS installation files
  2. Create a boot installer for macOS
  3. Choose the correct ‘createinstallmedia’ command

If you want to run macOS on an external drive such as an external hard drive, it is slightly different, so we recommend reading the article on how to install macOS on an external hard drive.;

What you need to create a bootable USB for Mac

There are two main things you will need to create your bootable macOS installation disk : a USB stick, as well as the installation files. Once you have those two things, the process shouldn’t take much longer.

A USB drive of at least 12 GB

We recommend a 12GB (or more) drive, as the installer for the Mojave beta was 5.68GB, while the High Sierra installer was 4.3GB.

We recommend a Flash memory device, as it will be faster. You should also use a USB flash drive USB 3.0 or USB type Type C. This may be your only option if you happen to have a Mac next generation by the type of connection offers.

If you have data on the drive you plan to use, you will need to transfer it to another drive or get a new drive as it will be formatted and erased entirely.

Installation files

Depending on the version of macOS you are running and the version you want to install, you will be able to get the installation files for ‘Software Update’ in ‘System Preferences’, Mac App Store, or you will have to get them elsewhere.

The Mac app store is probably the easiest option, but there may still be difficulties depending on the version of macOS your computer is running.

It goes without saying that you will need an internet connection to download the software and while installing it you will need to check the firmware or confirm your iCloud credentials.;

How to get macOS installation files

As we already mentioned, the way you get the installation files will depend on the version of macOS you are running and the version for which you want the installer. Next, we will see how to get the Catalina installers and previous versions.

How to get Catalina’s installer

If you want to obtain the installer for macOS that arrived last October 2019, macOS Catalina, follow these steps:

  1. If you are running Mojave on your Mac, you should go to ‘System Preferences> Software Update’.
  2. Please wait while your Mac checks for the latest macOS update.
  3. When I tell you that the operating system update is available for download, proceed with downloading the installation files.

But stop before clicking to install: you should copy this installation file before installing it on your Mac if you want to access it to make the installer upgradeable. Instructions for that below.

How to get macOS Catalina if you are running Catalina

If you’re already running Catalina, the software update won’t show you the software available for download, but you can still get the installation files from the Mac App Store:

  1. Open the Mac App Store.
  2. Access Catalina’s page, where you can click this link to Catalina in the Mac App Store .
  3. Now, if you click Get, your Mac will offer to download the installers.

Again, don’t click install directly, as you need the installation file for the next stage of this tutorial…

How to get old macOS installation files

With macOS Catalina, Mojave, or High Sierra installed, getting installation files for older macOS versions is a bit tricky. This is because when High Sierra was released, Apple removed the previous versions from its Mac App Store.

Fortunately, you can still do the following, explained below:

If you are not already running macOS Catalina, Mojave or High Sierra, or if you have access to a Mac that is not, you can follow these steps to download the installation files from a previous macOS:

  1. Start the Mac App Store on your Mac.
  2. Find the macOS version you want in the store (if you have already downloaded the version, look in the ‘Purchased’ tab).
  3. Click on the ‘Download’ button. If you already installed this version of macOS, you will see a message warning you that the macOS version is already installed on that computer. Click Continue to confirm that you still want to download the installer.
  4. Your Mac will download the installer to your ‘Applications’ folder. This process may take some time depending on the speed of your connection and whether you are using a wireless network. It took us about 10 minutes over Ethernet.
  5. If it starts automatically after downloading, mark that you don’t want to start the installation process on your Mac because doing so will remove the installers, and the installers are what you need. If it opens, close the installer.
  6. You will find the installation files in your ‘Applications’ folder, which you can access through the ‘Finder’.

How to create a bootable USB installer for macOS

Now that you have the installation files, we can move on to the process of creating the bootable installer USB. Please note that the createinstallmedia method described here does not work with OS X 10.6 Snow Leopard or earlier versions.

You will require macOS X 10.7 Lion or later. Also, the processes have changed slightly since Mavericks, so creating a boot install of macOS requires a single command in ‘Terminal’.

The createinstallmedia command makes it possible to create a bootable copy of an installer on any USB drive. Keep in mind that the createinstallmedia command erases anything on your external disk, so make sure you don’t need anything stored.

These are the instructions to follow to create your bootable USB; Keep in mind that there will be small adjustments depending on the installer you need:

  1. Plug in an external drive with at least 12GB of space as that’s what the installer will require.
  2. Start Disk Utility (press Command + spacebar and start typing Disk Utility).
  3. Before this next step, please note: If you are running High Sierra or later, you will need to click the ‘View Below’ dropdown menu for the minimize buttons. Choose Show all devices from the options. You will now see the external root drive in addition to the volume below it.
  4. Select the root drive in the sidebar (the next step won’t work if you just select the volume).
  5. Click on ‘Delete’.
  6. Choose Mac OS Extended (Journaled) as Format.
  7. Choose the GUID partition map as the outline.
  8. Your drive will probably be named ‘Untitled’ by default, you could give your drive a name like ‘macOS’ or ‘USB’. (Note that you will need to replace the term ‘MyVolume’ in the following createinstallmedia command with whatever name you give your drive.)
  9. Click on ‘Delete’.
  10. Wait while ‘Disk Uitlity’ creates the partition and configures the drive (this may take a few minutes).
  11. Then click Done.
  12. Open Terminal (the easiest way is to press Command + space bar and then start typing Terminal).
  13. Copy the text that corresponds to the version of macOS that you are installing in Terminal; You will find the text in the section below.
  14. Click on ‘Enter / Return’.
  15. The terminal will ask you for a password. This is your user password. Note that you won’t see characters appear as you type them, that’s fine. After typing your password, press Enter.
  16. The terminal will warn that you are about to erase the disk (so make sure there is nothing important on it!). If you want to continue, press Y and then Back. The process may take a while, you will see “Erase disk: 0% … 10% … 20% … 30% … 100% …
  17. Terminal will now spend a few minutes copying the installer file to your drive. “Copying installer files to disk … Full Copy” will appear in the Terminal window.
  18. When Terminal has finished copying the installer, you will see the words ‘Copy’ and ‘Done’ completed.
  19. Now that you have the installer on the external drive, you can use it to install multiple copies of macOS. Connect the external drive to the Mac where you want to install macOS.
  20. Start the Mac by holding down the Option / Alt key as it boots.
  21. Your Mac will display the ‘Startup Manager’, click on your external drive to select it as the startup disk. Your Mac will start in recovery mode.
  22. Click ‘Install macOS’ and then ‘Continue’. The macOS version should start to install on your Mac now.

You can also run the Mac operating system directly from an external drive instead of your built-in startup disk, this is useful if you are testing new versions of Mac OS.

Note that older versions of macOS used “applicationpath”, while newer versions did not: using the command will give you an error (we have the code for all versions of macOS and Mac OS X below).

Createinstallmedia Commands

The createinstallmedia command will be slightly different depending on the version of macOS you want to use.

Note: MyVolume can have a different name, for example it can be USB or similar. Check it in ‘Disk Utilities’, it is the name of the external disk you use.

Big Sur beta

sudo / Applications / Install \ macOS \ Big \ Sur \ Beta.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume –nointeraction –downloadassets

Katherine

sudo / Applications / Install \ macOS \ Catalina.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume

Mojave

sudo / Applications / Install \ macOS \ Mojave.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume

High saw

sudo / Applications / Install \ macOS \ High \ Sierra.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume

saw

sudo / Applications / Install \ macOS \ Sierra.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume –applicationpath / Applications / Install \ macOS \ Sierra.app

Captain

sudo / Applications / Install \ OS \ X \ El \ Capitan.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume –applicationpath / Applications / Install \ OS \ X \ El \ Capitan.app

Yosemite

sudo / Applications / Install \ OS \ X \ Yosemite.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume –applicationpath / Applications / Install \ OS \ X \ Yosemite.app

Mavericks

sudo / Applications / Install \ OS \ X \ Mavericks.app/Contents/Resources/createinstallmedia –volume / Volumes / MyVolume –applicationpath / Applications / Install \ OS \ X \ Mavericks.app

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