Proxmox installs on external SSD but Mac Pro 2013 always boots back to macOS

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viraj

New Member
Jan 9, 2026
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Hi everyone,

I’m fairly new to Proxmox and just getting started with a small home lab, so please bear with me if this is a basic question. I’m trying to install Proxmox VE on a Mac Pro 2013 (MacPro – trash can) and boot it from an external SSD, but I can’t get it to boot after installation.

Setup
  • Mac Pro Late 2013 (Intel)
  • Internal Apple PCIe SSD with macOS (still installed)
  • External SSD in a UGREEN USB-C NVMe enclosure (USB 3.2 Gen2)
  • Proxmox installer USB created on Windows using balenaEtcher
  • Proxmox installed to the external SSD
What happens
  • The Mac boots the Proxmox installer USB without any problem
  • Proxmox installs successfully to the external SSD
  • When the installer finishes, the system reboots
  • After reboot, the Mac always goes back into macOS
  • Holding Option (⌥) at startup only shows Macintosh HD
  • The external SSD never shows up as an EFI/boot option
I’ve tried reinstalling a couple of times but the behavior is always the same.

Questions
  1. Has anyone managed to boot Proxmox from an external SSD on a Mac Pro 2013?
  2. If yes, what kind of enclosure did you use (USB-SATA, USB-NVMe, Thunderbolt, etc.)?
  3. Did you need something like rEFInd or OpenCore to make it boot, or should it work directly?
I’m mainly trying to understand whether this setup is supposed to work on this hardware, or if I should be looking at a different approach.

Thanks a lot for any pointers.
 
Last edited:
Thank you for responding and for sharing your thoughts.

I’ve already disabled SIP and installed rEFInd successfully. rEFInd itself is loading reliably now, so that part is working as expected.

The issue I’m running into is after the Proxmox installation completes. The external USB-NVMe SSD does not show up as a bootable option afterward — neither in Apple’s Option boot picker nor as a valid loader that rEFInd can actually chainload.

More specifically:
  • rEFInd does load and scan correctly
  • It sometimes detects a Linux/GRUB entry, but attempting to boot it fails with grubx64.efi not found or results in a kernel panic
  • I’ve tried explicitly adding a manual menuentry in refind.conf pointing to the expected grubx64.efi path, but the SSD still doesn’t boot successfully after installation
  • SIP is disabled, and rEFInd is installed on the internal EFI
At this stage, the challenge seems to be limited to getting the installed system on the external SSD to boot consistently, rather than the initial rEFInd setup itself. Any thoughts? Is the enclosure not supportive?

I’m using a standard ext4/LVM layout (not ZFS) during installation.
 
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