Unable to Install Catalina on an External Drive. This issue can occur because of the T2 Security Chip found in recent vintage Macs. The T2 chip protects your Mac by default from being booted from an external device. This prevents someone from walking up to your Mac with a USB flash drive, booting your Mac, and accessing your files. When trying to download the application, they find themselves with a 22 MB file instead of the full 6 GB Mojave App. Well, the 22 MB mini-installer work pretty well for a number of tasks. One thing, however, you can't use it to create a macOS Catalina or Mojave flash drive installer. For this task, you require the full size 6 GB App.

• Can I Install Catalina On An External Drive
• Can I Install Catalina On An External Drive
• Install Catalina On External Drive From Big Sur

Now that you've finished setting up OpenCore, you're finally able to boot, main things to keep in mind:

• Enable BIOS settings optimal for macOS
• Read up on the OpenCore Multiboot Guide(opens new window) as well as Setting up LauncherOption(opens new window)
  • Mainly relevant for those running a single drive for multiple OSes
• And a copy of the General Troubleshooting page
• Read up on the macOS Boot Process
  • Can help first time installers better understand where they may be getting stuck
• And a ton of patience

# Double checking your work

One last thing we should go over before booting is how your EFI is setup:

And a reminder that slowgeek site is your friend:

# Booting the OpenCore USB

So you're now ready to finally put the USB stick into your computer and boot off of it. Remember that most laptops and some desktops will still default to the internal drive with Windows, and you'll need to manually select OpenCore in the BIOS boot options. You'll need to check in the user manual or use a bit of google to find out what Fn key accesses the BIOS and boot menu(ie. Esc, F2, F10 or F12)

Once you boot the USB, you'll likely be greeted to the following boot options:

1. Windows
2. macOS Base System (External) / Install macOS Catalina (External)
3. OpenShell.efi
4. Reset NVRAM

For us, Option 2. is the one we want. Depending how the installer was made, it may report as either 'macOS Base System (External)' if created in Linux or Windows and 'Install macOS Catalina (External)' if created in macOS.

# macOS Installer

So you've finally got the installer booted, got through the verbose and hit the installer! Now that you've gotten this far, the main things to keep in mind:

• Drives you wish to install macOS on must be both of GUID partition Scheme and APFS
  • High Sierra on HDD and all Sierra users will need to use macOS Journaled(HFS+)
• The drive must also have a 200MB partition
  • By default, macOS will setup freshly formatted drives with 200MB
  • See the Multiboot Guide(opens new window) for more info on partitioning a Windows Drive

Once you start the installation, you will want to wait until the system restarts. You will once again want to boot into OpenCore, but rather than selecting your USB installer/recovery - you will want to select the macOS installer on the hard drive to continue installation. You should get an apple logo, and after a few minutes you should get a timer at the bottom saying 'x minutes remaining'. This may be a good time to get a drink or snack as this will take a while. It may restart a couple more times, but if all goes well, it should finally plop you at the 'Setup your Mac screen'

You're in! 🎉You will want to go through the Post-Installation pages to finish setting up your system.

Boot Camp Assistant User Guide

You can use Boot Camp Assistant to install Windows 10 on your Intel-based Mac.

Newer Mac computers use a streamlined method to install Windows on your Mac. To find out whether your Mac uses this method, see the “Learn more” section in the Apple Support article Install Windows 10 on your Mac with Boot Camp Assistant. If your Mac is an older model that requires an external USB drive, follow the instructions in Install Windows on your older Mac using Boot Camp instead.

What you need

• The keyboard and mouse or trackpad that came with your Mac. If they aren’t available, use a USB keyboard and mouse.

• A full-installation, 64-bit version of Windows 10 on a disk image (ISO file) or other installation media.

  You can download a Windows 10 Disc Image (ISO File) from Microsoft.

• Sufficient free storage space on your startup drive. For information about the amount of free space needed, see the Apple Support Article Install Windows 10 on your Mac with Boot Camp Assistant.

Before you begin

Before you install Windows, make sure you back up important files.

You can use Time Machine or any other method to back up your files. For information about backing up files, see Back up your files with Time Machine and Ways to back up or protect your files.

Perform the installation

Can I Install Catalina On An External Drive

On your Mac, do the following steps in order.

Step 1: Check for software updates

Before you install Windows, install all macOS updates.

1. On your Mac, log in as an administrator, quit all open apps, then log out any other users.

2. Choose Apple menu > System Preferences, click Software Update, then install all available macOS updates.

   If your Mac restarts after installing an update, open Software Update again to install any additional updates.

Step 2: Prepare your Mac for Windows

Boot Camp Assistant prepares your Mac by creating a new partition for Windows named BOOTCAMP and downloading the Boot Camp support software.

Important: If you’re using a Mac notebook computer, connect it to a power source before continuing.

1. On your Mac, open Boot Camp Assistant , located in /Applications/Utilities.

2. At the Introduction screen, click Continue.

   The system is checked for total available disk space. Older Time Machine snapshots and cached iCloud files are removed to make space for Boot Camp. This process may take a long time to complete (you can click the Stop button to skip this process).

3. If you have only one internal disk, choose the Windows ISO image, specify the partition size by dragging the divider between the macOS and Windows partitions, then click Install.

4. If you have multiple internal disks, follow the onscreen instructions to select and format the disk you want to install Windows on and to choose the Windows ISO image.

   • If you select your startup disk: You can create an additional partition for Windows. Specify the partition size by dragging the divider between the macOS and Windows partitions.

   • If you select an APFS-formatted disk: You can either create an additional partition on the disk for Windows, or erase the entire disk and create a partition for Windows. If you choose to create an additional partition, specify the partition size by dragging the divider between the macOS and Windows partitions.

   • If you select a non-APFS-formatted disk: You can erase the entire disk and create a partition for Windows.

   If Boot Camp is already present on the disk you select, you also have the option to uninstall it.

   Important: You can’t resize the partition later.

When this step is complete, the Windows installer starts.

Step 3: Install Windows

Can I Install Catalina On An External Drive

1. In the Windows installer, follow the onscreen instructions.

   When the installation is finished, your Mac automatically restarts using Windows.

2. Follow the onscreen instructions to set up Windows.

Step 4: Install Boot Camp on Windows

Install Catalina On External Drive From Big Sur

After installing Windows, Boot Camp drivers that support your Mac hardware start installing.

Note: If the support software doesn’t install automatically, you need to install it manually. For instructions, see the Apple Support article If the Boot Camp installer doesn't open after using Boot Camp Assistant.

1. In the Boot Camp installer in Windows, follow the onscreen instructions.

   Important: Do not click the Cancel button in any of the installer dialogs.

   If a message appears that says the software you’re installing has not passed Windows Logo testing, click Continue Anyway.

   You don’t need to respond to installer dialogs that appear only briefly during installation, but if a dialog asks you to install device software, click Install.

   If nothing appears to be happening, there may be a hidden window that you must respond to. Look behind open windows.

2. When the installation is complete, click Finish.

3. After your Mac restarts, follow the instructions for any other installers that appear.