Testing Debian 12 ARM64 VM on Raspberry Pi 5 KVM: Pitfalls and Solutions

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After successfully setting up a Home Assistant OS (HAOS) VM on my Raspberry Pi 5 (KVM/libvirt approach), I wanted to test a minimal Debian 12 ARM64 VM for InfluxDB and Grafana.

My Setup So Far

  • Host: Raspberry Pi 5, 16GB RAM
  • Hypervisor: KVM / QEMU / libvirt
  • Guest: HAOS running smoothly
  • Management: Cockpit & virt-manager

Trying Debian 12 VM: Where virt-install Fails (and Why)

First attempt: I tried to launch a Debian 12 ARM64 VM using virt-install. Example command (does NOT work for ARM64 on RPi5):

virt-install -v --name influxdb-grafana \
  --ram 3072 \
  --vcpus 2 \
  --disk path=~/debian12/influxdb-grafana.img,cache=none,size=25 \
  --nographics \
  --osinfo debian12 \
  --arch aarch64 \
  --cdrom ~/debian12/debian-12.12.0-arm64-netinst.iso

Pitfall:
Despite using correct UEFI firmware, virt-install on ARM64/KVM can stall at boot, consume 100% CPU, and give a cryptic Synchronous Exception at 0x... error. This happens because:

  • The ARM64 QEMU stack (especially on Raspberry Pi) relies on precise firmware, boot flags, and sometimes kernel quirks.
  • Even with qemu-efi-aarch64 and UEFI, virt-install may not properly initialize all necessary hardware, particularly the disk image and CPU.
  • The disk image file does not exist by default and must be created beforehand.
  • ARM64 support is less mature than x86, so best practice is usually manual disk and VM creation.

Solution: QEMU Launch

Step 1: Create a Raw Disk Image and get Debian 12 image

Create a 25GB disk image for Debian: qemu-img create -f raw ~/debian12/influxdb-grafana.img 25G

Download image: wget https://ftp.thm.de/debian-cd/debian-12.12.0-arm64-netinst.iso

Step 2: Run QEMU Directly

Boot the Debian 12 installer using QEMU command-line:

qemu-system-aarch64 \
  -machine virt \
  -cpu cortex-a76 \
  -m 3072 \
  -bios /usr/share/qemu-efi-aarch64/QEMU_EFI.fd \
  -drive file=~/debian12/influxdb-grafana.img,format=raw \
  -cdrom ~/debian12/debian-12.12.0-arm64-netinst.iso \
  -nographic
  • Make sure you have downloaded the ARM64 netinst ISO from a reliable mirror (e.g. ftp.thm.de or cvut.cz).
  • The disk image (influxdb-grafana.img) must exist before running QEMU.
  • Use -bios to point to the UEFI firmware, typically /usr/share/qemu-efi-aarch64/QEMU_EFI.fd.

Result:
This method starts the installer without triggering the “Synchronous Exception” error and works on Raspberry Pi 5 (KVM/qemu/libvirt stack).

During the Debian 12 ARM64 installation on the Raspberry Pi 5, be aware that the installer can appear to hang at around 83% with the message Configuring linux-image-6.1.0-39-arm64 (arm64) for up to 30 minutes (or more). Afterward, it may repeat this slow kernel configuration process for an updated version, showing Configuring linux-image-6.1.0-40-arm64 (arm64) and again taking a long time. Both steps involve unpacking the kernel and building the initramfs - tasks that are exceptionally slow on ARM64 virtual machines, even with a fast SSD. If you see these messages, don’t panic or reboot - just be patient, and the installation will eventually continue!

During installation, I noticed the CPU usage shot up to 100% especially while configuring packages like Configuring linux-image-6.1.0-39-arm64 (arm64)- and with all ARM cores working hard, my Raspberry Pi 5 warmed up enough that my little cooling fan started spinning in earnest! In fact, a quick check showed this:

doma@rpi5:~/debian12 $ vcgencmd measure_temp
temp=58.7'C

Step 3: Import the Debian VM for Cockpit & Libvirt Management

Under construction… Might not work

After installing everything and testing your VM with manual QEMU (the installation may take more then 1 hour), you may want to stop it and re-import for easier management in Cockpit/libvirt.

To stop the manually running VM, first find and kill the QEMU process:

ps aux | grep influxdb-grafana.img
kill <pid>

Now register your existing disk image in libvirt with virt-install --import so your VM shows up in Cockpit:

This lets you manage and monitor your Debian ARM64 VM via Cockpit or virsh!

sudo virt-install \
  --name influxdb-grafana \
  --ram 3072 \
  --vcpus 2 \
  --disk path=~/debian12/influxdb-grafana.img,format=raw,bus=virtio \
  --import \
  --osinfo debian12 \
  --arch aarch64 \
  --graphics none \
  --boot uefi,loader=/usr/share/qemu-efi-aarch64/QEMU_EFI.fd \
  --cpu host \
  --network bridge=br0,model=virtio,mac=52:54:00:4a:19:03

Final Notes

  • LIBVIRT/virt-install for ARM is less predictable than on x86, so manual qemu-img and qemu-system-aarch64 often “just work”.
  • For reliable network and storage performance, always check your firmware and disk image setup.
  • If you run into similar exceptions, try different QEMU CPU models or firmware versions; regressions are common.