Proxmox VM Boot Troubleshooting

Fri, 01 May 2026 00:00:00 +0000

Proxmox VM Boot Troubleshooting#

What Was Established#

Ubuntu VMs can hang during the boot process at apparmor.service (displayed as “staring apparmor.service - L:oad appArmor profiles…”).
In Proxmox, this specific hang was caused by an iGPU (…)

Coffee Lake iGPU Passthrough Freeze & Recovery#

Issue: Coffee Lake iGPU passthrough to an Ubuntu VM causes the Proxmox VM to freeze on boot.
Immediate Recovery Steps (run from Proxmox host console):
1. Stop the frozen VM: qm stop <VMID> --force or kill -9 <PID> via ps aux | grep qemu.
2. Remove iGPU from VM config: Edit /etc/pve/qemu-server/<VMID>.conf and remove hostpci lines and GPU-related args: lines.
3. Reset host iGPU state: Edit /etc/modprobe.d/pve-blacklist.conf and comment out blacklist i915.
4. Reboot host: update-initramfs -u -k all && reboot.
5. Verify host recovery: lspci | grep -i vga and lsmod | grep i915.
Proper Re-configuration Steps:
1. Enable IOMMU: Update /etc/default/grub with GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt", then update-grub && reboot.
2. Verify IOMMU Groups: find /sys/kernel/iommu_groups/ -type l.
3. Add iGPU via UI: VM → Hardware → Add PCI Device → Select iGPU → Check “All Functions” & “PCI-Express” → DO NOT check “Primary GPU”.
Advanced/Alternative Configuration:
- GRUB Parameters: quiet intel_iommu=on iommu=pt pcie_acs_override=downstream,multifunction nofb nomodeset video=efifb:off
- Host Blacklist: echo "blacklist i915" >> /etc/modprobe.d/pve-blacklist.conf
- VM Config (args):
```
args: -device vfio-pci,host=00:02.0,addr=0x18,x-igd-gms=1,driver=vfio-pci
args: -device vfio-pci,host=00:02.1,addr=0x18.1,driver=vfio-pci
args: -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
args: -set device.vga.ramfb=off
args: -set device.vga.driver=vfio-pci
```
- VM Hardware Requirements: Machine q35, BIOS OVMF (UEFI), Display Default (not SPICE).
- Ubuntu VM Guest: Install Intel graphics drivers, add i915.enable_guc=2 to kernel parameters, ensure early KMS start.

Sources#

ingested/chats/103-Troubleshooting Coffee Lake iGPU Passthrough on Proxmox.md
ingested/chats/101-Troubleshooting Slow Ubuntu VM Boot.md

Passthrough on homelab

Proxmox VM Boot Troubleshooting

Proxmox VM Boot Troubleshooting#

What Was Established#

Coffee Lake iGPU Passthrough Freeze & Recovery#

Sources#