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Test Ubuntu Core with QEMU

You can test Ubuntu Core without specific hardware from within a virtual machine, using either Multipass or QEMU (https://www.qemu.org/).

  • Multipass has integrated support for the latest Ubuntu Core images and is quicker to get started with
  • QEMU is more configurable and can boot either a supported image or a custom image, with or without TPM emulation and full disk encryption.

Using QEMU is covered below. For details on using Multipass, see Test Ubuntu Core with Multipass.

Test QEMU

To test Ubuntu Core with QEMU on Ubuntu, first install the qemu-kvm package and test it with kvm-ok (a utility that comes with the cpu-checker package):

sudo apt install qemu-kvm
$ kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used

To ensure compatibility with the required UEFI features in Ubuntu Core, also install the OVMF package:

sudo apt install ovmf

Download the preferred Ubuntu Core image for your device platform. See Supported platforms for links to images.

By default, images are compressed with xz and can be expanded from the Linux command line with the following command:

xz -d <image-name>.img.xz

The above command will remove the original archive leaving only the uncompressed image which will change after being booted. To keep a copy of the original archive, add the -k argument.

Boot an Ubuntu Core image with QEMU

The exact QEMU command to run will depend on your host hardware capabilities and architecture, such as available memory and CPU cores, but the following should work in the majority of cases on x86_64-based hardware.

For UEFI boot to work, first copy both OVMF_CODE.secboot.fd and OVMF_VARS.ms.fd to a user-accessible location. In the following examples, we assume they’re in the local directory. On Ubuntu-based systems, the following commands will copy them to the local directory:

cp  /usr/share/OVMF/OVMF_CODE.secboot.fd .
cp /usr/share/OVMF/OVMF_VARS.ms.fd .

Without TPM emulation

To test Ubuntu Core without TPM emulation, omit the three lines that reference the TPM device:

qemu-system-x86_64 \
 -enable-kvm \
 -smp 1 \
 -m 2048 \
 -machine q35 \
 -cpu host \
 -global ICH9-LPC.disable_s3=1 \
 -net nic,model=virtio \
 -net user,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80  \
 -drive file=OVMF_CODE.secboot.fd,if=pflash,format=raw,unit=0,readonly=on \
 -drive file=OVMF/OVMF_VARS.ms.fd,if=pflash,format=raw,unit=1 \
 -drive "file=<ubuntu-core-image.img>",if=none,format=raw,id=disk1 \
 -device virtio-blk-pci,drive=disk1,bootindex=1 \
 -serial mon:stdio

With TPM emulation and full disk encryption

We recommend first installing a test snap that emulates TPM in software with libtpms (see the swtpm documentation for implementation details):

snap install --edge test-snapd-swtpm

The path to the snap’s libtpms-based socket (/var/snap/test-snapd-swtpm/current/swtpm-sock) is passed to the QEMU command:

sudo qemu-system-x86_64 \
 -enable-kvm \
 -smp 1 \
 -m 2048 \
 -machine q35 \
 -cpu host \
 -global ICH9-LPC.disable_s3=1 \
 -net nic,model=virtio \
 -net user,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80  \
 -drive file=OVMF_CODE.secboot.fd,if=pflash,format=raw,unit=0,readonly=on \
 -drive file=OVMF/OVMF_VARS.ms.fd,if=pflash,format=raw,unit=1 \
 -chardev socket,id=chrtpm,path="/var/snap/test-snapd-swtpm/current/swtpm-sock" \
 -tpmdev emulator,id=tpm0,chardev=chrtpm \
 -device tpm-tis,tpmdev=tpm0 \
 -drive "file=<ubuntu-core-image.img>",if=none,format=raw,id=disk1 \
 -device virtio-blk-pci,drive=disk1,bootindex=1 \
 -serial mon:stdio

Reset the TPM

If you wish to run a new clean image after previously running QEMU with the emulated TPM, you will need to reset the emulated TPM state. The safest way to do this is to purge remove and reinstall the emulator snap:

snap remove --purge test-snapd-swtpm
snap install --edge test-snapd-swtpm

Boot an ARM64 Ubuntu Core image

It is possible to boot Ubuntu Core arm64 images with qemu-system for arm64 on x86_64 systems. Additional requirements can be installed by running the following:

sudo apt install qemu-efi-aarch64 qemu-system-arm

To run the arm64 image without TPM, execute:

qemu-system-aarch64 -machine virt -cpu cortex-a57 -smp 2 -m 4096 \
                        -bios /usr/share/AAVMF/AAVMF_CODE.fd \
                        -netdev user,id=net0,hostfwd=tcp::8022-:22 \
                        -device virtio-net-pci,netdev=net0 \
                        -drive if=virtio,file="ucarm.img",format=raw \
                        -device virtio-gpu-pci \
                        -device virtio-keyboard \
                        -device virtio-mouse \
                        -serial mon:stdio

Due to QEMU emulating a different architecture, the full installation can take some time.

It is also possible to run with an emulated TPM by installing the same test-snapd-swtpm snap as for x86. For this to work, you need to first copy the UEFI variables from your system to the local directory. This only needs to be done once, before the first boot of a clean image:

cp /usr/share/AAVMF/AAVMF_VARS.ms.fd .

QEMU can now be run:

sudo qemu-system-aarch64 -machine virt -cpu cortex-a57 -smp 2 -m 4096 \
        -drive file=/usr/share/AAVMF/AAVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \
        -drive file=AAVMF_VARS.ms.fd,if=pflash,format=raw,unit=1 \
        -netdev user,id=net0,hostfwd=tcp::8022-:22 \
        -device virtio-net-pci,netdev=net0 \
        -drive "file=uc.img",if=none,format=raw,id=disk1 \
        -device virtio-blk-pci,drive=disk1,bootindex=1 \
        -chardev socket,id=chrtpm,path=/var/snap/test-snapd-swtpm/current/swtpm-sock \
        -tpmdev emulator,id=tpm0,chardev=chrtpm \
        -device tpm-tis-device,tpmdev=tpm0 \
        -object rng-random,filename=/dev/urandom,id=rng0 \
        -device virtio-rng-pci,rng=rng0,id=rng-device0 \
        -device virtio-gpu-pci \
        -device virtio-keyboard \
        -device virtio-mouse \
        -serial mon:stdio

As before, due to QEMU emulating a different architecture the full installation can take some time.

Accessing the VM

In the the above QEMU commands, we forward the virtual SSH port 22 to port 8022 on the host. To access this configuration from your host machine, type the following:

ssh -i <path-to-private-key> <sso-username>@localhost -p 8022

In addition to SSH access, QEMU will start a VNC-shared console which can be accessed at vnc://localhost:5900 on the system. Some configurations may also forward port 80 to 8090 for any web server application you wish to install in the VM.

For a brief introduction on how to get started with Ubuntu Core, see Using Ubuntu Core.

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