Open Core Legacy Patcher: Upgrading to Sonoma

AI created image of a hall full of obsolete Macintosh-style computers

This post details the process of upgrading a Mac running MacOS 13 Ventura with Open Core Legacy Patcher to MacOS 14 Sonoma.

When Apple classes a Mac as too old to receive macOS patches, it's usually a signal to the owner that a shiny new device is in order (if, of course, the owner kept it that long and didn't upgrade sooner).

A lot of the time, however, while the hardware of said device may no longer be performant, it may still be completely capable of running the latest macOS version, if only there was some way of forcing it to install. Oh wait, there is: Open Core Legacy Patcher.

Download OCLP

Installing a too-new version of macOS on your ancient device isn't the point of this article–the documentation from OCLP is pretty good, see here:

No, given that the process for installing includes installing custom EFI bootloaders, performing a major version upgrade was surprisingly less well documented. So, if you're using one version of macOS thanks to OCLP, and want to upgrade to another (specifically, Sonoma), here's a good place to start.

This process requires a 32GB USB stick for the bootable installer. If you don't have one of these, some people report success by choosing Build and Install OpenCore to the internal disk, then following the built-in macOS (via the App Store). While this might work, it's pretty useful to have the bootable installer in case something goes wrong and you need to reinstall from scratch, especially if this is your only Mac.

Download the latest version of OCLP (this is important as the newer macOS versions may have specific fixes or support for newly deprecated hardware).

Download the macOS Installer

Choose Create macOS Installer then Download macOS Installer if you haven't got the latest version downloaded already.

Screenshot showing the main interface of OpenCore Legacy Patcher 1.4.2
OpenCore Legacy Patcher screenshot: options to download macOS installer or use an existing one.
OpenCore Legacy Patcher screenshot: showing a progress bar of the download of macOS 14.4

Create a bootable USB drive

Once downloaded, you'll be prompted to select a USB device to turn into a bootable installer.

For Sonoma, a 16GB USB stick will be too small, so you'll need one with 32GB capacity.

You'll be prompted for your password, and once you've confirmed you want to override/reformat your USB stick, OCLP will start building your USB.

It says it can take over 30 minutes, and it's really not lying. Go and make some tea or something while you wait. Maybe walk the dog.

OpenCore Legacy Patcher screenshot: showing the progress of writing the macOS install to USB stick

Install OpenCore to USB

Once the process is complete and verified, OCLP will ask if you want to install OpenCore on the stick. This is what allows what would otherwise not be able to run on your hardware to start up anyway, so choose Yes. It will build and ask for confirmation to Install to disk.

Another option might've been to Build and install OpenCore to the macOS internal drive first, therefore giving the main bootable partition the more recent drivers & EFI boot partition. Perhaps it wouldn't also be required on the USB stick then, but hey, this also worked.
OpenCore Legacy Patcher screenshot: prompt showing that the USB creation is complete. Asking whether to install OpenCore to this disk.
OpenCore Legacy Patcher screenshot: Showing build of OpenCore is complete and asking whether to install it to disk.
OpenCore Legacy Patcher screenshot: showing the progress of installing OpenCore to USB stick

Boot from the USB installer

Now you can reboot your Mac, holding option/alt when it boots. You need to choose the USB stick's EFI option here, and then on the next screen, choose the install macOS option.

To distinguish from the built-in EFI partition (because/if you have an OCLP installation already) and the one on the USB, remember that macOS always shows external drives as yellow, even on the boot up screens.

Begin the installation

Once in the macOS recovery/install view, choose the 'install macOS' option to begin the upgrade. Choose to install it over the existing drive and it'll automatically know it needs to upgrade the installation, so don't go into Disk Utility or fiddle with the disk/partitions at all.

Once the installation begins, it will reboot a couple of times, and when it does, you'll need to make sure to hold option/alt on start-up so you can choose the external USB EFI partition again. Once in the EFI parition, choosing the macOS option instead of install macOS should be fine, as it'll know to continue the install.

If you've ended up in the wrong partition midway through the installation, you'll probably get an error or question-mark on screen. Just power the Mac back down, and reboot into the external EFI partition again.

Install OpenCore to disk

Once finished and booted back into macOS, you may (should?) get a prompt from OCLP to say that you're still booted from the USB EFI parition, and ask if you want to install to the internal disk. Choose OK, then Install to disk.

OpenCore Legacy Patcher screenshot: prompt explaining that OCLP detects system has booted from the USB's EFI partition. Asks if this should be installed to internal disk.
OpenCore Legacy Patcher screenshot: OpenCore build complete, prompt asking for confirmation to install this to the internal disk.

Once done, shut your Mac down, remove the USB stick then boot it back up. It should automatically make it back to the Desktop without requiring any manual intervention.

Post-Install Root Patch

I didn't need to run this, I assume OCLP handled this as part of the OpenCore step previously.

To confirm, choose the Post-Install Root Patch option and it will check to see if anything is required, so install these if required.

OpenCore Legacy Patcher screenshot: showing the Post-Install Menu and that the root volume was last patched recently from the current version of OCLP (so no changes were required).

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