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I'm attempting to use OpenCore Legacy Patcher to update an Late-2008 aluminum unibody MacBook (MacBook5,1) to run Monterey (macOS 12).

What I did:

  • On the target MacBook5,1, I downloaded the OpenCore app version 1.4.2 and built an OpenCore USB for Monterey 12.7.4
  • I booted the machine from the OpenCore Monterey install USB
  • I reformatted the system drive (Samsung SSD, internal) to a single 4TB APFS volume via disk utility
  • I ran the Monterey installer onto this partition

What went wrong:

  • After installation, the machine rebooted.
  • Things are supposed to look like this, but did not.
  • OpenCore Install Monterey USB is the only boot option (holding down alt)
  • Selecting this option leads immediately to the "prohibit symbol" (gray circle with a slash) and no further boot option.
  • I tried resetting PRAM and SMC a few times to no effect

Research so far:

  • I searched for an explicit walk-through and I found confusing information scattered across various forums (reflecting various historical states of OpenCore Legacy Patch, perhaps). There are some walk-throughs and forum posts for Monterey with MacPro5,1, but this is a desktop machine, I'm on the MacBook5,1 (a laptop).

  • OpenCore Legacy Patcher does support MacBook5,1. I am attaching the install/boot USB stick through a USB2.0 hub to avoid USB1.0 support issues; I saw this mentioned a couple times but am not sure if it still applies.

  • Up through the "Building and installing OpenCore" steps, everything proceeds as planned.

  • This boot troubleshooting section may be relevant. After installation, the machine seems to lose the system drive entirely but also loses the EFI boot options for the OpenCore Install Monterey USB? Sadly, none of those scenarios, nor any in this list, seem to match the "prohibit logo" behavior I'm getting?

  • There is troubleshooting information for the () Prohibited Symbol here.. The solution is to "ensure you're booting OpenCore before the macOS installer in the boot picker. Reminder that the option will be called EFI Boot", however this boot option vanished immediately after installation. The other explanation is that there is something wrong with the USB drive, which doesn't seem plausible given that it is brand new and that I just ran the Monterey installer from it.

For now, I've re-installed Mojave and will try all of the above tomorrow (in case something different happens).

Giacomo1968
  • 58,727
MRule
  • 405

2 Answers2

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I managed to create a situation where there is no EFI boot partition on either the main system disk, or the OpenCore Legacy Patcher Monterey install USB.

The older mac models cannot natively boot later operating systems. OpenCore's EFI bootloader provides the patches to make this possible. If you attempt to boot an unsupported operating system through the normal (Apple) bootloader, you'll see the symbol.

The OpenCore Legacy Patcher instructions are slightly vague on this, but ideally one wants to click "Install OpenCore" for both the main system disk and the newly created USB thumb-drive installer, before attempting the install.

What happened was likely this:

  • I installed OpenCore on the main system disk, which made it possible to boot the Monterey installer USB thumb drive.
  • During installation, I erased my system disk, removing its EFI boot partition. Thus, the new system disk was not bootable.
  • My OpenCore Legacy Patcher USB thumb drive did not have an EFI boot sector of its own, and so could not be used to boot the system either.

It's unclear to me whether the "Create macOS Installer" feature is supposed to create the EFI boot sector on the thumb drive, or whether I clicked something that skipped this step. The online OpenCore Legacy Patcher walk-through does not cover these steps in full resolution.

For future reference, one can manually install OpenCore onto the USB installer after it was created to make sure. Assuming your system drive is already partitioned as you would like, you should also be able to install OpenCore to the system disk and then run the patched installer, provided you do not alter the drive format in the process.

MRule
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Creating the USB install flash drive alone does not put an EFI boot partition on it. At least Version 1.5.0 of OCLP suggests that it be installed, right after all the installation files have been copied to the flash drive.

lapisque
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