Creating a Multi-OS Installer Flash Drive

As an IT support specialist, I provide services to numerous commercial and private clients. One of my most common activities is the installation of operating systems (OS) on Mac and Windows computers. As a result, I used to carry several bootable flash drives, each with the installer for a different operating system. This includes various versions of macOS, Windows, and Linux distributions.

I recently decided that it would be much more efficient if I could put all the different operating systems I need on a flash drive. As a result, I created a drive that contains multiple versions of macOS and Windows 10. The drive was created on a Mac running macOS Big Sur, but it can run on a Mac or Windows computer. It can then be used to install macOS or Windows 10 on a Mac or Windows 10 on a PC.

Read on to learn how to create a multi-OS installation flash drive using a Mac.

Flash Drive Preparation

The first stage of the process is to prepare the flash drive you will be using by erasing and formatting it. The following are the necessary steps.

  1. choose utilities in Seeker and open disk utility.
  2. Connect your flash drive and check if show all devices is marked on View menu in disk utility.
  3. You should see your flash drive listed below External in the left pane disk utility. Click on it and then click on Delete.

  1. take a ride Name (I called him Operating systems) and select Mac OS Extended (Journaled) as Format and GUID Partition Map as Scheme.

  1. Click Delete.
  2. When the removal process is complete, click Made.

Burn the first version of macOS to a flash drive

You are now ready to write your first macOS flash drive installer. Let’s start with the latest version, which is macOS Big Sur.

The first step is to download the macOS Big Sur installer. Apple has made it quite easy, and this page contains download links for all recent versions of macOS, along with instructions on how to create a single bootable installer. just click macOS Great South under the title Download macOS. This will take you to the app store where you simply click on GET. After a few seconds, you will be asked if you are sure you want to download macOS Big Sur and you should click download files.

Once the download is complete, you can dismiss any attempt to start installing macOS. It is important that the installer is now downloaded to your Applications map. that is called Install macOS Big Sur.

To write the installer to the desired partition on your flash drive, open Terminal what will you find in utilities in Seeker. Then type the following command.

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sudo /Applications/Install\ macOS\ Big\ –volume /Volumes/OperatingSystems

This command will be different if you are writing a non-Big Sur version and you need to check the correct syntax under the heading Use “createinstallmedia” command in terminal on the How to create a bootable installer for macOS page. Another component that may be different will be the name of the volume after /Volumes what is in my case Operating systems.

after pressing input You will be prompted for an administrator password. You will then need to confirm that you want to continue and the operation will continue. This will take some time, depending on the speed of your flash drive, and you will see progress from 0 to 100% as files are copied to the drive.

You now have a bootable flash drive containing the macOS Big Sur installer. You are ready to continue adding additional macOS installers to the drive.

disk partition

First you need to partition the drive.

To return to Disk Utility and click on your flash drive in the left pane. You will see that under the drive name you now have the name of your first volume which is Install macOS Big Sur.

Click Pulp and you will be presented with a partition window. Within this window you can define the partitions you need, along with their sizes.

For now, let’s create an extra partition, which we’ll use to install macOS Catalina.

Click on + create an additional partition and then give it a Name. He Format ought Mac OS Extended (Journaled) as before, I Size 12 GB should be enough.

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Click apply when ready, click to confirm Pulp in the next window. The operation will take some time and then you should see a window informing you that the operation was successful. Click Made to close the window.

You can now download the macOS Catalina installer the same way you did with Big Sur. Then go back to Terminal and type a command similar to the one used for Big Sur, but changing the name of the installer and the name of the destination volume. In this case, it would be the following command.

sudo /Applications/Install\ macOS\ –volume /Volumes/macOSCatalina

Re-enter your administrator password, confirm that you want to continue, and the operation will continue.

You now have a bootable flash drive with two partitions containing installers for different versions of macOS. You can then continue with the process of creating new partitions, downloading the desired installers and writing them to the flash drive. Apple provides instructions for versions as old as OS X El Capitan and it’s unlikely you’ll need a version earlier than this unless you’re running a very old Mac.

Add a Windows 10 partition

We will now add a Windows 10 installation partition to the drive.

To return to disk utilityclick on your flash drive and select Pulp again. This time add a partition called windows 10formatted MS-DOS (FAT) and 8 GB in size.

Click apply and then Pulp like before.

Now you need to download the Windows 10 ISO file (installer) from Microsoft. You can do this by visiting their page to download a Windows disk image (ISO file). For the purposes of this guide, I will assume that you are downloading the 64-bit International English version. Once you have downloaded the file, make a note of its full name in your downloads map. Then go back to Terminal and type the following command to mount the downloaded ISO file.

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mount hdiutil ~/Downloads/

then open it disk utility and make a note of the name of the disk image you just created, below disk images.

Now you have to go back to Terminal and type the following command.

rsync -avh –progress –exclude=sources/install.wim /Volumes//* /Volumes/W10

Now you need to install a package manager called Homebrew. To do this, use the following command Terminal.

/bin/bash -c “$(curl -fsSL”

You will need to enter your administrator password and confirm the operation. Once installed, type the following command.

prepare wimlib installation

Finally, enter the following command to write the Windows 10 installer to the Windows partition on the flash drive.

wimlib-imagex split /Volumes//sources/install.wim /Volumes/W10/sources/install.swm 3800

Testing the installer

To check if your flash drive is working properly, first turn off your computer. Then start the computer with the flash drive connected and hold down the key option key when it starts. After a while, you should see all the boot options available to you. First it will be the hard drive of your Mac, then you will see all the versions of the macOS installer you have installed on the flash drive, as well as the Windows installer, which is called, EFI boot. Clicking on any of them will launch the corresponding installer, allowing you to continue installing that operating system.


As an IT support professional, having a set of macOS installers, along with a Windows 10 installer, on the same flash drive is invaluable. Although we created the drive using a Mac, the drive can also be used to install Windows 10 on a Windows PC.

Gone are the days when we had to carry around multiple USB flash drives.

Categories: How to
Source: HIS Education

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