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Installing ESXi 8 on Older Hardware Using Proxmox (2025 Guide)

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By Matt Black 4 min read

I recently reinstalled Proxmox on my Dell homelab workstation and decided to tackle VMware ESXi 8. My old Dell has a 3rd gen Intel i7, 16GB RAM, and dual 1TB SSDs - decent specs but showing its age.

While you can technically install ESXi 8 directly on older hardware, VMware has discontinued support for pre-Skylake processors, which means potential compatibility issues and instability with future updates. Instead, I chose to nest ESXi within Proxmox. This gives me access to both platforms for learning, and if I mess up ESXi, I can easily rebuild it without affecting my main hypervisor.

This streamlined guide shows how to run VMware ESXi 8 within Proxmox VE on unsupported hardware - perfect for home labs and educational testing (not for production use).

Disclaimer: This guide was developed with AI assistance. It’s provided “as-is” without warranty. By following these instructions, you acknowledge you do so at your own risk. The author is not liable for any issues.

Prerequisites

  • Proxmox VE 8.x host
  • 8GB+ RAM (16GB recommended)
  • 50GB+ storage
  • Intel/AMD processor with virtualization extensions
  • Admin access to Proxmox

ESXi Licensing (Post-Broadcom, Free Edition)

  • License: Applied automatically during installation from the free ISO
  • Expiration: Never — not a 60-day evaluation
    • Note: A 60-day evaluation pop-up may appear during setup — this seems to be a holdover from pre-Broadcom installer behavior. If your license status shows “vSphere 8 Hypervisor” with “Never expires,” you’re fully on the free edition.
  • Limitations: Max 8 vCPUs per VM, no vCenter, no vMotion, no HA/DRS, no backup APIs
  • Support: Community-only; no official Broadcom support

Download Steps1

  1. Create account at support.broadcom.com
  2. Navigate: Cloud icon → VMware Cloud Foundation → My Downloads
  3. Click “Free Software Downloads available HERE”
  4. Search “VMware vSphere Hypervisor” and download latest ISO

Step 1: Enable Nested Virtualization2

  1. Check current nested virtualization status:
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    # Check status (Intel/AMD)
cat /sys/module/kvm_intel/parameters/nested
cat /sys/module/kvm_amd/parameters/nested
  2. If the output shows “N” or “0”, enable nested virtualization based on your CPU type:
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    # Enable (Intel)
echo "options kvm-intel nested=Y" > /etc/modprobe.d/kvm-intel.conf
modprobe -r kvm_intel && modprobe kvm_intel

# Enable (AMD)
echo "options kvm-amd nested=1" > /etc/modprobe.d/kvm-amd.conf
modprobe -r kvm_amd && modprobe kvm_amd

    Note: If the modprobe commands fail (e.g., “module is in use”), reboot Proxmox to apply the changes.

Step 2: Create VM in Proxmox 2

  1. Upload the ESXi ISO to Proxmox storage:
    • Option A (Web UI): Go to Datacenter → Storage → local → ISO Images → Upload
    • Option B (SCP): Use scp filename.iso root@proxmox-ip:/var/lib/vz/template/iso/
    • Option C (wget): SSH to Proxmox and use wget to download directly to /var/lib/vz/template/iso/
  2. Create a new VM with these essential settings:
    • OS: Linux 6.x - 2.6 Kernel
      • CD/DVD: Select the ESXi ISO you uploaded
    • System: OVMF (UEFI), EFI disk enabled, SCSI: VMware PVSCSI
    • Disk: SATA, 32GB+, SSD emulation, Discard enabled
    • CPU: 2+ cores, Type: host (or kvm64 for compatibility)
    • Memory: 8192MB minimum
    • Network: Intel E1000 or vmxnet3

Step 4: Make CPU Fix Permanent

Boot ESXi with the CPU fix one more time

  1. After installation completes and ESXi reboots, it will fail to start normally (CPU compatibility error)
  2. Press ESC at the VMware splash screen to access boot options
  3. Navigate to the ESXi boot entry and add the CPU flag:
    • Look for the ESXi boot entry in the boot menu (it will say something like “VMware ESXi” or show the hard drive)
    • Do NOT select the CD-ROM entry
    • Press Tab on the ESXi boot entry
    • Add allowLegacyCPU=true to the end of the boot line
    • Press Enter to boot
  4. Boot into ESXi and enable SSH:
    • Open a web browser and go to the ESXi host IP address
    • Log in with the root credentials you set during installation
    • Go to Host → Actions → Services → Enable Secure Shell (SSH)

Edit Boot Configuration

  1. SSH into the ESXi host:
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    ssh root@esxi-ip
  2. Navigate to the boot directory and backup the configuration:
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    cd /bootbank
cp boot.cfg boot.cfg.bak
  3. Edit the boot configuration file:
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    vi boot.cfg
  4. Find the kernelopt= line and add allowLegacyCPU=true to the end:
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    kernelopt=autoPartition=FALSE earlyPrintk=FALSE allowLegacyCPU=true
  5. Save the file (:wq in vi) and reboot the ESXi host

Step 5: Post-Installation Configuration

Add Storage

  1. Shutdown the ESXi VM from Proxmox
  2. In Proxmox, add additional storage:
    • Go to Hardware → Add → Hard Disk
    • Use SATA interface and VMDK format
  3. Start the ESXi VM
  4. Create a new datastore via the ESXi web UI using the added disk

Troubleshooting

Boot Issues: Use UEFI manual launch if boot menu doesn’t appear

CPU Errors Persist: Verify boot.cfg syntax - ensure space before allowLegacyCPU=true

Network Issues: Try different adapter types (E1000 vs vmxnet3)

Poor Performance: Increase RAM, use host CPU type, enable SSD emulation

Conclusion

This setup provides an excellent VMware learning environment without dedicated hardware. While unsuitable for production, it’s perfect for testing, certification prep, and home labs.

References

  1. Jonas Werner - How to Find OEM ESXi Installer ISOs on Broadcom’s Webpage, Jonamiki Blog ↩

  2. RavenHawkTech - VMware Nested within Proxmox Hypervisor, YouTube Tutorial ↩ ↩2

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This post is licensed under CC BY 4.0 by the author.