Reviving a Mac Pro 5,1 for ESXi 6.7 or 7.0

9 minute read

Recently I was offered a free “decommissioned” Mac Pro (Mid 2010) to re-purpose as I pleased. I like the idea of giving new life to an old Mac, the only issue with this free computer, was that it doesn’t run new software - but we can fix that. And so began my journey to install ESXi 7.0 and get Big Sur running on a Mac from 2010.

While old, it was a beefy Mac Pro with great specs for visualising macOS VMs, and I’ve needed an always-on workhorse for Mac Admin and Jamf Pro tasks. So, what can a free computer get you these days:

Mac Pro (Mid 2010) MacPro5,1
Intel Xeon W3530 2.80 GHz Processor 
AMD something something card.

The plan for this new-old Mac is to host daily workflows:

  • Automated macOS testing workflows using a combination of AutoDMG, vFuse, VMWare for testing packages, DEP and beta releases.
  • Host a dedicated AutoPkg environment. I’m also interested to try PatchBot, just announced for vJNUC2020.

TL;DR - The Process

  1. Install the highest supported ESXi version for your hardware
  2. SSH in and use the esxicli to upgrade to desired ESXi version
  3. Before rebooting to apply the update, edit the /altbootbank/boot.cfg file, append allowLegacyCPU=true to the kernelopt line
  4. reboot to apply the update
  5. If the edit was successful it will bypass the incompatible CPU warning
  6. When you create VMs, you may need to add monitor.allowLegacyCPU = “true” in the .vmx file.

If you get stuck, read on.

ESXi Versions & Compatibility

If your host Mac supports the latest ESXi, then just install that and forget about this hot mess.

If however, you are using an older hand-me-down Mac, you have the option to hack a newer version of ESXi onto unsupported hardware - which is very achievable. The main reason you would do this is guest VM OS compatibility.

Newer versions of macOS require a higher virtualhw.version, which in turn, require a higher ESXi version.

  • macOS 10.14 Mojave - Minimum virtualhw.version = "14" requires ESXi 6.7
  • macOS 10.15 Catalina - Minimum virtualhw.version = "15" requires ESXi 6.7 Update 3 (VMWare KB Article)
  • macOS 11 Big Sur 🤷‍♂️ - virtuallyGhetto has a post with it running on ESXi 6.7

Let’s move on.

Create an EXSi USB Installer

Check out these very detailed guides on VirtuallyWired, complete with pictures and terminal output:

Note: Start by creating an installer that is compatible with your host Mac.

Install ESXi

With the USB installer inserted, boot the Mac holding option and follow the prompts. Configure your network preferences and enable SSH.

Upgrade ESXi

After installing the compatible version of ESXi, it’s time to upgrade it to an incompatible version.

Originally I started down a rabbit hole trying to modify the ESXi installer to trick it into thinking the CPU was compatible - this process is much easier.

Hot Tip It is easy to confuse ESXi installable versions and patches. Installers are suffixed by the build number ESXi-6.7.0-8169922-standard and patches are suffixed by the release date ESXi-6.7.0-20200804001-standard.

SSH into your ESXi host:

  1. Enter Maintenance Mode

     vim-cmd /hostsvc/maintenance_mode_enter
  2. Allow http downloads through the firewall

     esxcli network firewall ruleset set -e true -r httpClient
  3. Find your desired version - Refer to the VMWare article for build numbers

     esxcli software sources profile list -d
  4. Install the desired version and do not restart to apply updates

     esxcli software profile update -d -p ESXi-6.7.0-8169922-standard
  5. At this point, there is a new boot.cfg file staged for the next reboot. View this file cat /altbootbank/boot.cfg and confirm the desired build at the end of the file (eg build=6.7.xxxx).

  6. Edit the file vi /altbootbank/boot.cfg and append allowLegacyCPU=true to the kernalopts line. It should look like this:

     kernelopt=installerDiskDumpSlotSize=2560 no-auto-partition allowLegacyCPU=true
     modules=jumpstrt.gz --- useropts.gz <<snip snip blah blah long list of modules that go on and on and on>>
  7. You can now reboot to complete the update.

Apply ESXi Patches

When you apply ESXi patches, changes to the boot.cfg should persist. I recommend you check the new /altbootbank/boot.cfg before you reboot.

ESXi patches are cumulative, so you can install the latest patch available for your release. To find that patch, your can grep the output of of the esxcli software sources profile list command from step 3. For example:

# Find the desired patch
esxcli software sources profile list -d | grep 6.7.0-2020
# Install the patch
esxcli software profile update -d -p ESXi-6.7.0-20200804001-standard
# Check the kernalopts still have allowLegacyCPU=true
cat /altbootbank/boot.cfg
# Reboot to apply patch

Creating VMs

When creating VMs, you must consider the ESXi and macOS requirements, ensuring the correct virtualhw.version = "xx" is used. If you use vFuse, use the --esx to create a pre-allocated ESX-type VMDK and you may also need to add monitor.allowLegacyCPU = “true” in the .vmx file.

If you have ever been down the path of using a Mac as an ESXi hypervisor, you are probably familiar with some of the challenges. A collection of helpful resources: