How to create a bootable installer for macOS Ventura

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It’s handy to have an external, bootable macOS Ventura installer, but you practically have to fight Apple to create one. Here’s what you need to do.

In Apple’s ideal world, you let your Mac update to macOS Ventura, and you never have to think about it. In reality, however, Macs go awry, and having a bootable external installer preloads download time and speeds up reinstalling Ventura when you’re in a bind.

Also, if you’re responsible for installing Ventura on a dozen Macs, you have better things to do with your time than waiting for it to download on each one separately if you don’t have caching of content somewhere on your network.

So, as has always been the case, it’s handy and convenient to have an external drive that you can use to install a fresh copy of macOS.

But Apple thinks allowing external bootable drives is a security risk. For longtime Mac users, the risk of allowing a bootable drive is low and the downside of blocking them is high.

What do you need

  1. An external hard drive
  2. A macOS installer

In theory, the external drive could be just about any hard drive, SSD or USB flash drive – and you probably want it to be USB-C. Best results come from NVMe USB-C or Thunderbolt drives, and speed is good on those. Although you can use a hard drive, it will be unbearably slow.

Whereas with a USB drive, the speed might not be what makes you pull your hair out. Many USB flash drives just won’t boot and there’s nothing you can do about it, but try another one.

Disks in a RAID will also not work, nor will disks attached to the network.

Whatever drive you have, it should be formatted as Mac OS Extended and have enough storage available for the macOS installer.

Apple has previously stated that this means it must have at least 14GB of space, but that was for installers of macOS Monterey or earlier. More is better.

Get the macOS installer

Speaking of installers, Apple keeps the current one and several previous ones available in the App Store. Launch the App Store app on your Mac and search for “macOS Ventura” when available.

Download it. The app you downloaded will be called “Install macOS Ventura” and will be at least 12 GB in size.

By default, the Mac will try to launch this installer as soon as it is downloaded. Exit the installer immediately, because once installed, it will remove the installer application.

If the app is in your Downloads folder, move it to the Applications folder.

Prepare the external drive

Connect the external drive to your Mac. These next steps will erase the drive, so be sure to copy any data you have on it.

With the drive plugged in, launch the Terminal app. Copy this line, replacing the last part “BootDrive” with the name of your external drive:

sudo /Applications/Install macOS Ventura.app/Contents/Resources/createinstallmedia—volume /Volumes/BootDrive

Replace last term

Replace the final term “BootDrive” with the name of your external drive

Terminal will then prompt you to create a bootable drive with macOS Ventura on it. You will be asked for your administrator password and you will have to confirm that you want the disk erased.

It’s likely that Terminal will show an alert that it wants to access files on a removable volume. Click OK.

When you see “Install media now available on” and the name of your external drive, you can quit Terminal.

We can’t stress this enough: test the player you’ve created before relying on it.

Using the external hard drive

So far most things are as they always have been, but it’s when you actually want to boot from the external drive that things change. It’s also changed a lot since the move to Apple Silicon, and enough that the process of using an external drive is quite different on it and on Intel Macs.

Intel Macs have a T2 security chip that will block what could be unauthorized access to your Mac. To allow you to use an external hard drive on an Intel Mac, you must:

  1. Restart your Mac Intel
  2. Hold down Command-R the moment you see the Apple logo
  3. When prompted, choose your username from the list displayed
  4. Enter your administrator password for this user
  5. From the menu bar, choose Utilities, Startup Security Utility
  6. Login
  7. Click to select Allow booting from external or removable media

It’s quite simple, but there is a catch.

If your only reason for having an external startup drive is in case of problems with the Mac’s own drive, you must have gone through this process first. You won’t be able to do this if your Mac’s internal disk is severely damaged.

Having done so, however, the process of booting an Intel Mac from an external drive is now simple.

Using External Boot Drives on Intel Macs

  1. Turn off your Mac
  2. Connect the external hard drive
  3. Turn on the Mac and immediately hold down the Option key
  4. Let go of the Option key when you see a list of bootable volumes

Using External Boot Drives on Apple Silicon Macs

Allowing external drives to boot requires a slightly different process on Apple Silicon. You’re always telling the Mac to stop blocking external drives, and you always have to do that before the Mac’s disk goes bad.

  1. Shut down the Mac
  2. Press and hold the power button
  3. Release when you see one or more readers and a Choice section
  4. Select Choice and click Continue
  5. When the Mac boots into recovery mode, select a Mac user whose password you know.
  6. Login as this user
  7. Ignore all options in the pop-up list and choose instead Boot Security Utility from Utilities menu
  8. Click to select the Mac’s internal drive, then click Open
  9. Follow the password prompts and select Security policy
  10. In the Security Policy window that appears, click to select Reduced security
  11. Then click OKAY
  12. Under the Recovery menu, choose Stop

You have now configured this Mac – or rather this user of this Mac – to boot from external drives. To do this, you must then:

  1. Turn off your Mac
  2. Plug in the external hard drive
  3. Press and hold the Mac’s power button
  4. Release the power button when you see a list of bootable volumes
Apple brings up other apps rather than its own macOS, especially older ones.  But many recent versions of macOS can be found with an App Store search.

Apple brings up other apps rather than its own macOS, especially older ones. But many recent versions of macOS can be found with an App Store search.

Using Different Versions of macOS

If your Mac can’t run macOS Ventura, putting it on an external drive won’t help. The App Store listing for Ventura, however, will tell you if it’s compatible with your Mac.

Right now when Ventura is new that won’t be a problem, but over time there will be another side to all of this that will arise. You cannot boot your Mac from an external volume with an older macOS than that machine is capable of running.

Over time, so it’s not only good to create an external boot drive, it’s important to keep doing it every few years.

We will discuss how to create an external scratch disk shortly.

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