Here’s a narrative-style document that captures the story and learnings behind my Proxmox adventure with Windows 11 and Server 2025
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Installing Windows 11 and Server 2025 on Proxmox: A Journey from Friction to Flow
An annotated tale of quirks, commands, and clean installs
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Introduction
This wasn’t just a how-to. It was a discovery process—a technically nuanced journey to install Windows 11 and Windows Server 2025 cleanly and repeatably on Proxmox to be a headless machine. Along the way, I hit walls, found workarounds, and finally distilled a series of qm commands that work every time.
Here’s my behind-the-scenes story, the blood, sweat and tears so to speak. That includes the 6.30am starts following the 11.30 pm finishes. Work, sleep, eat, repeat; about five days that felt like a month. The hardware was delivered on day 2.
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- TPM and Secure Boot: Necessary, but Elusive
The Challenge
Windows 11 refuses to install without a TPM 2.0 module and Secure Boot—both of which are non-trivial in a virtual environment like Proxmox. Early attempts failed silently or gave obscure Windows error codes.
The Discovery
Eventually, I learned to change Proxmox settings instead of editing the install iso register:
–tpmstate0 local-lvm:1,size=4M,version=v2.0
–efidisk0 local-lvm:1,format=raw,efitype=4m,pre-enrolled-keys=1
This combination made Windows 11 happy. Secure Boot worked without needing to disable driver signing or patch the ISO register.
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- VirtIO Drivers: The Invisible Disk Problem
The Linux Proxmox config Challenge
Both Windows 11 and Server 2025 saw no disks at install time. Without drivers, the installer had no idea how to handle VirtIO devices.
The Discovery - a Microsoft download
Attaching the VirtIO drivers ISO to a second CD-ROM solved this. But it took experimentation to figure out which driver folders to navigate during install (typically vioscsiw11amd64 or NetKVM for network).
I sourced the VirtIO drivers ISO from the official Fedora project hosting page:
https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/latest-virtio-win.iso
This URL always points to the latest stable build of the VirtIO driver ISO, maintained by the Red Hat/Fedora community. It includes all required drivers for:
• VirtIO SCSI/Block (for storage disks)
• NetKVM (for networking)
• QXL (for SPICE graphics if used)
• Balloon and Guest Agent supportI mounted this ISO to ide2 in the Proxmox VM configuration to provide drivers during Windows setup:
Not having this or even knowing about it would be a real “gotcha”: a project breaker.
Final Form:
qm set 110 –ide2 local:iso/virtio-win.iso,media=cdrom
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- qm Trial and Error: The Ultimate Sandbox
The Challenge
Proxmox’s qm tool is powerful but unforgiving. Missteps in config would lead to:
• Hanging installs
• Unbootable VMs
• Broken UEFI configs
• “Missing boot device” screensThe Process
I created multiple VMs, deleted them, tried again—often tweaking one line at a time. Key learnings:
• --machine q35 is a must.
• --bios ovmf is needed for UEFI.
• Without --scsihw virtio-scsi-pci, disks don’t behave properly.
• The order of --boot order=virtio0 matters.⸻
- Post-Install Nuances
The Challenge
Even after a successful install, things weren’t perfect.
The Fixes
• QEMU Guest Agent: Needed for graceful shutdowns and clipboard.
• ISO Detachment: Prevented Windows from booting into installer again. This is a major very simple problem. Just eject it! And di not select auto boot after install so you have a chance to do the ejection.
• VirtIO Network Drivers: Manual install post-Windows setup.Key Commands:
qm set 110 –agent enabled=1
qm set 110 –ide2 none
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- What Didn’t Matter (But Seemed Like It Might)
False Leads
• --ostype: win10 works fine even for Windows 11 and Server 2025.
• numa, balloon: Not critical for initial setup.
• Complex UEFI options: Defaults are good enough if you’re not doing GPU passthrough or nested virtualization.⸻
Conclusion
What continued as a frustrating, opaque process eventually became a clean, repeatable installation blueprint. The real lesson? These setups are less about documentation and more about exploration. Once you know the map, the journey takes minutes. Until then, it feels like crossing a minefield in the dark.
Now the field is cleared—and I’ve left the flags up for the next traveler.