This tutorial for installing macOS Catalina using OpenCore has been adapted for Proxmox from Kholia’s OSX-KVM project and Leoyzen’s OpenCore configuration for KVM. You can get the full sourcecode on my GitHub here.
If you’d like to use Clover instead, use my older tutorial, but OpenCore works better!
I’ll assume you already have Proxmox 6.1 or 6.2 installed. You also need a real Mac available in order to fetch the OSK key.
Your Proxmox host computer’s CPU must support SSE 4.2, so for Intel your CPU must be at least as new as Nehalem, which was the first CPU generation to bear the “Core” i5/i7 branding. Older CPUs will cause the finder to repeatedly crash after installation completes (with an Illegal Instruction exception in the graphics code).
Modern AMD CPUs also support SSE 4.2 and will work with this guide.
First step: Create an installation ISO
The easiest installer to build is a recovery image, which will download Catalina during installation. Download and run fetch-macOS.py in a terminal to download the Catalina recovery image from the Apple software distribution server (this can be run on Linux, Proxmox, or on a Mac):
This results in a ~500MB “BaseSystem.dmg” file in the current directory. Convert that dmg into an “iso” like so if you’re building this on macOS:
hdiutil convert BaseSystem.dmg -format RdWr -o Catalina-installer.iso mv Catalina-installer.iso.img Catalina-installer.iso
Or like so if you’re building this on Linux:
# Install the dmg2img package and... dmg2img BaseSystem.dmg Catalina-installer.iso # Or use qemu-img from the qemu-utils package to do it instead: qemu-img convert BaseSystem.dmg -O raw Catalina-installer.iso
The result is actually a raw disk image, not a true ISO, but Proxmox has better tools for picking and re-using ISO images than disk images. Upload the “ISO” to your Proxmox server’s ISO store (typically /var/lib/vz/template/iso).
If you won’t have an Internet connection available to Catalina during installation, or your network can’t provide an IP address by DHCP you’ll need to build an offline installer instead. Building the offline installer requires you to have a Mac, here are the instructions.
Prepare an OpenCore image
We’ll be using OpenCore as a bootloader for Catalina. This has several improvements over my old Clover-based tutorial, like fixes to screen resolution problems, better CPU feature support, and better FileVault compatibility, and is recommended for all future builds.
Download the latest OpenCore.iso.gz release from my repository, unpack it, and upload it to Proxmox’s ISO store at /var/lib/vz/template/iso. Although it has a .iso file extension, this is actually a hard disk image.
Fetch the OSK authentication key
macOS checks that it is running on real Mac hardware, and refuses to boot on third-party hardware. You can get around this by reading an authentication key out of your real Mac hardware (the OSK key). Save the first block of C code from this page as smc_read.c. In a command prompt, change into the same directory as that file and run:
xcode-select --install # If you don't already have gcc gcc -o smc_read smc_read.c -framework IOKit ./smc_read
It’ll print out the 64 character OSK for you. Make a note of it.
Every Mac uses the same OSK, so don’t be surprised that it doesn’t look like a random string!
Create the VM
From the Proxmox web UI, create a new virtual machine as shown below.
In the Options page for the VM, ensure that “use tablet for pointer” is set to “Yes”.
In the Hardware page for the VM, add a second DVD drive at IDE0, set it to use your Catalina-installer.iso.
Don’t try to start the VM just yet. First, SSH into your Proxmox server so we can make some edits to the configuration files.
Edit /etc/pve/qemu-server/YOUR-VM-ID-HERE.conf (with nano or vim). Add this line, being sure to substitute the OSK you extracted earlier into the right place:
args: -device isa-applesmc,osk="THE-OSK-YOU-EXTRACTED-GOES-HERE" -smbios type=2 -device usb-kbd,bus=ehci.0,port=2
(A USB keyboard is added here because macOS doesn’t support QEMU’s default PS/2 keyboard.) Ensure the args are all on a single line!
We also need to add a -cpu argument. If your host CPU is Intel, add this to the end of the “args” line:
This will pass through all of the features that your CPU supports. OpenCore’s config will pretend to macOS that the CPU’s model name is Penryn for compatibility.
If your CPU has AVX support but no xsave/xsaveopt support, you need to add “,-avx” to the end of that -cpu argument to disable AVX. This is because macOS won’t boot if avx is present but xsave/xsaveopt is absent. (It’s unclear whether any real Intel CPUs fall into this category. You can check the features your CPU supports in Proxmox with “grep flags /proc/cpuinfo”)
If your host CPU is AMD, or the above argument doesn’t work for you, use this more-compatible alternative:
This pretends that your CPU is Penryn, which will keep macOS happy even if your host CPU is AMD, and adds a bunch of newer required and optional CPU features on top. Features that your host CPU doesn’t support will be ignored (a warning will be printed to the console during launch with
qm start 1xx), but note that macOS won’t work without SSE4.2 support.
Now find the lines that define the two “ISOs” (ide0 and ide2), and remove the “,media=cdrom” part from them. Add “,cache=unsafe” in its place. This will treat these as hard disks rather than DVD drives.
Save your changes, return to the Options tab, and change the boot order to put IDE2 (the OpenCore image) first. Your final VM configuration file should resemble this:
args: -device isa-applesmc,osk="..." -smbios type=2 -device usb-kbd,bus=ehci.0,port=2 -cpu host,kvm=on,vendor=GenuineIntel,+kvm_pv_unhalt,+kvm_pv_eoi,+hypervisor,+invtsc balloon: 0 bios: ovmf bootdisk: ide2 cores: 4 cpu: Penryn efidisk0: vms:vm-100-disk-1,size=1M ide0: isos:iso/Catalina-installer.iso,cache=unsafe,size=2094688K ide2: isos:iso/OpenCore.iso,cache=unsafe,size=150M machine: q35 memory: 4096 name: catalina net0: vmxnet3=...,bridge=vmbr0,firewall=1 numa: 0 ostype: other sata0: vms:vm-100-disk-0,cache=unsafe,discard=on,size=64G,ssd=1 scsihw: virtio-scsi-pci smbios1: uuid=... sockets: 1 vga: vmware
On Proxmox, run “echo 1 > /sys/module/kvm/parameters/ignore_msrs” to avoid a bootloop during macOS boot. To make this change persist across Proxmox reboots, run:
echo "options kvm ignore_msrs=Y" >> /etc/modprobe.d/kvm.conf && update-initramfs -k all -u
Unlike Clover, OpenCore doesn’t require Proxmox’s OVMF package to be patched, so if you had previously installed my
pve-edk2-firmware package, and you don’t have any Clover VMs left, you can revert to the vanilla Proxmox package by running “apt-mark unhold pve-edk2-firmware; apt install pve-edk2-firmware”. If you still have Clover VMs that need it, you can continue to use my patched package, it’ll work too.
Now start up your VM, it should boot to the OpenCore boot picker:
Press enter to boot the “macOS Base System” entry and the installer should appear.
Our virtual hard drive needs to be erased/formatted before we can install to it, so select the Disk Utility option. Follow the steps below to format the disk:
Now we’re ready to begin installation!
After the first stage of installation, the VM will reboot. Pick the “macOS Installer” entry to continue installation:
The VM will finish installation and reboot itself a second time. Now the installation is complete, so choose the name of your main disk to boot (mine’s called Main):
Answer the initial install questions, and you’ll be logged on! (Note that you’ll want to hold off on logging into your iCloud account until you’ve configured your SMBIOS to your liking)
Make the OpenCore install permanent
We’re currently booting using OpenCore from the attached OpenCore ISO. Let’s install that to the hard drive instead. Pop open Terminal and run “diskutil list” to see what drives we have available.
Use “sudo dd if=<source> of=<dest>” to copy the “EFI” partition from the OpenCore CD and overwrite the EFI partition on the hard disk. The OpenCore CD is the small disk (~150MB) that only has an EFI partition on it, and the main hard disk is the one with the large Apple_APFS “Container” partition on it.
In my case these EFI partitions ended up being called disk1s1 and disk2s1 respectively, so I ran “sudo dd if=/dev/disk1s1 of=/dev/disk2s1” (note that if you get these names wrong, you will overwrite the wrong disk and you’ll have to start the installation over again!).
Now shut down the VM, and remove both the OpenCore and the Catalina installer drives from the Hardware tab. On the Options tab, edit the boot order to place your SATA disk as the first disk. Boot up. If everything went well, you should see the OpenCore boot menu, and you can select your “Main” disk to boot Catalina:
I found that I was unable to wake Catalina from sleep using my mouse or keyboard. If you encounter the same problem, you can either disable system sleep in Catalina’s Energy Saver settings to avoid the issue, or you can manually wake the VM up from sleep from Proxmox by running:
qm monitor YOUR-VM-ID-HERE
Editing your OpenCore/EFI settings
The Configuration.pdf that explains the OpenCore config.plist file can be found along with the OpenCore release on my GitHub.
To mount your EFI partition in macOS so you can edit config.plist, first check the “identifier” of your EFI partition in the terminal:
~$ diskutil list /dev/disk0 (external, physical): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *512.1 GB disk0 1: EFI EFI 209.7 MB disk0s1 2: Apple_APFS Container disk1 511.9 GB disk0s2
Then you can mount it like so:
sudo mkdir /Volumes/EFI
sudo mount -t msdos /dev/disk0s1 /Volumes/EFI
Now you can edit /Volumes/EFI/OC/config.plist with your favourite text editor to make your changes. (TextEdit is not a great choice because it likes to insert curly quotes into the file and otherwise break things, there are some dedicated plist editors available such as XCode).
If you’re unable to boot macOS, you can edit the config.plist using the “UEFI Shell” option in the OpenCore boot menu instead.
Enter “FS0:” and press enter to open up the first available filesystem, then run “edit EFI\OC\config.plist” (if the file isn’t found, try switching to another filesystem like fs1:). When you’re done editing, press control+Q to exit, “Y” to save, then run “exit” to return to the OpenCore menu. You need to reboot for your changes to take effect.
In config.plist, set Misc/Boot/Timeout to a non-zero value to allow the default boot option be chosen automatically after that delay in seconds. I’ve disabled this by default because it causes the installer ISO to re-enter its main menu instead of continuing the second stage of installation.
To boot macOS in Verbose mode to diagnose boot problems, edit config.plist to change the “bootargs” in the NVRam section from “keepsyms=1” to “keepsyms=1 -v”.
Changing screen resolution
To change macOS’ screen resolution, you need to edit the UEFI/Output/Resolution setting in config.plist, the default is 1920×1080@32.
You should be able to change this to any of the modes that the system OVMF menu offers (hit F2 at the start of guest boot and choose “Device Manager/OVMF Platform Configuration” to see which resolutions are available).
Because there is no guest video acceleration available for macOS, video performance is poor.
In Google Chrome in the guest you will need to toggle off the setting to “use hardware acceleration when available” to improve issues with elements not being drawn or flickering (especially video). Safari may be a better choice.
macOS’s built in “Screen Sharing” feature offers dramatically better framerates and latency than Proxmox’s browser-based VNC console, so if you have a real Mac to act as a viewing console, you can enable that in the VM’s “Sharing” settings and connect to the VM using the Screen Sharing app from your Mac instead:
Apparently Screen Sharing is also compatible with VNC clients like RealVNC, so you should be able to connect to it from Linux or Windows consoles using RealVNC.
The real magic bullet for video performance is to pass through a compatible video card using PCIe passthrough (though note that Catalina does not support most NVidia cards). This offers near-native performance. You can read more about how I’m using PCIe passthrough on my own installation here.
Since I want to use this as my primary computer, I want to use a USB keyboard and mouse plugged directly into Proxmox, rather than sending my input through the web VNC console.
Proxmox has good documentation for USB passthrough. Basically, run “qm monitor YOUR-VM-ID-HERE”, then “info usbhost” to get a list of the USB devices connected to Proxmox:
qm> info usbhost
Bus 3, Addr 12, Port 6, Speed 480 Mb/s
Class 00: USB device 8564:1000, Mass Storage Device
Bus 3, Addr 11, Port 5.4, Speed 12 Mb/s
Class 00: USB device 04d9:0141, USB Keyboard
Bus 3, Addr 10, Port 5.1.2, Speed 12 Mb/s
Class 00: USB device 046d:c52b, USB Receiver
Bus 3, Addr 9, Port 14.4, Speed 12 Mb/s
Class 00: USB device 046d:c227, G15 GamePanel LCD
Bus 3, Addr 8, Port 14.1, Speed 1.5 Mb/s
Class 00: USB device 046d:c226, G15 Gaming Keyboard
In this case I can add my keyboard and mouse to USB passthrough by quitting qm, then running:
qm set YOUR-VM-ID-HERE -usb1 host=04d9:0141
qm set YOUR-VM-ID-HERE -usb2 host=046d:c52b
This saves the devices to the VM configuration for you. You need to reboot to have the new settings apply. Note that the emulated USB3 device doesn’t work with macOS, so don’t set “usb3=1”.
You can also pass through USB devices by passing through an entire USB controller using Proxmox’s PCIe passthrough feature, which gives much better compatibility.
FileVault now works with OpenCore, so you can encrypt your boot disk by using the option in macOS’ system security preferences. But be certain to keep a copy of your recovery key and keep your backups up to date.
Using an odd number of CPU cores
macOS doesn’t like it if your CPU has a weird number of cores, like 3 or 6. You can fix this on the Hardware tab. Edit the Processors settings, and tick the Advanced box. Round up the number of cores you want (e.g. 3) to a nice power of two (4, 8, 16, etc) and use that for the “Cores” setting, but set the “VCPUs” setting to the number of cores you actually want to be used (3), like so:
This will cause macOS to see that system supports a maximum of 4 cores, but that one core is absent since it hasn’t been hotplugged yet, so macOS will only use 3 cores.
Another approach is to use an odd number of sockets in order to make the core count a power of two. e.g. to pass 6 cores, set Sockets to 3, and Cores to 2 (or 4 to pass both threads per core).
Proxmox doesn’t let us set the number of threads per core in the VM config, so if you want to pass every thread of a hyperthreaded 6-core CPU, and have them reported to the guest as hyperthreads, add
-smp 12,sockets=3,cores=2,threads=2 to your “args”, or for a 56-core hyperthreaded CPU,
If your host CPU is Intel, and you used “-cpu host” in your VM config file (explained above), you can use Nested Virtualisation in macOS. This allows you to run VirtualBox VMs, the Android emulator, or Docker inside your macOS guest. You just need to tweak your Proxmox system config to enable this as explained in the Wiki:
macOS’s Hypervisor framework doesn’t support nested virtualisation on AMD host CPUs, but apparently VirtualBox uses their own virtual machine driver which does work (I haven’t tried this myself). I imagine this will stop working in the next version of macOS, since they’re planning to add a bunch of restrictions on third-party kexts and might force VirtualBox to use Hypervisor.framework.
Fixing “guest boots to UEFI shell”
If your guest ends up booting to the UEFI shell instead of showing the OpenCore boot menu, especially if you’ve just updated OpenCore to a new version, you’ll need to edit the guest’s UEFI boot entries to fix this.
At the very start of guest boot, hit F2 to enter guest UEFI settings.
First we’ll remove the old entries. Choose the Boot Maintenance option, then Boot Options -> Delete Boot Option. Use the spacebar to tick any old Clover or OpenCore entries (avoid ticking the EFI Internal Shell option, you want to keep that!). Select “Commit Changes and Exit”.
Now we’ll add the correct entry for OpenCore back in. Select Add Boot Option. Navigate through the device tree to EFI/BOOT/BOOTx64.efi and select it, name this new option “OpenCore” or similar. Again Commit Changes and Exit.
Go to the Change Boot Order and move OpenCore to the top. Commit Changes and Exit.
Now back out to the main menu and choose Reset, and you should successfully boot into OpenCore this time.