Ubuntu Core: Preparing a virtual machine with graphics support

Tutorials
1
Key Value
Summary A guide to setting up an Ubuntu Core virtual machine with support for hardware graphics using qemu-virgil.
Categories iot
Difficulty 3
Author alan.griffiths@canonical.com

Ubuntu Core: Preparing a virtual machine with graphics support

Overview

Duration: 0:30

When developing for Ubuntu Core it is often convenient to work in a virtual machine [VM]. Unfortunately, the archive build of qemu on Ubuntu doesn’t support graphics passthrough. This is a quick guide to setting up an Ubuntu Core VM using qemu-virgil.

Setup qemu with graphics support

Duration: 1:00

As the default build of qemu on Ubuntu doesn’t support graphics, we will use a handy snap containing a build that enables this:

$ sudo snap install qemu-virgil
$ sudo snap connect qemu-virgil:kvm

Check the snap is working:

$ qemu-virgil --version

Download and prepare the Ubuntu Core image

Duration: 2:00

We also download an Ubuntu Core image. On an x86 computer download the ubuntu-core-20-amd64.img.xz image from here:

https://cdimage.ubuntu.com/ubuntu-core/20/stable/current/

Now, uncompress the image and move it to a convenient location:

$ unxz ~/Downloads/ubuntu-core-20-amd64.img.xz
$ mv ~/Downloads/ubuntu-core-20-amd64.img ~/snap/qemu-virgil/common/

Initialize a VM with the Ubuntu Core image

Duration: 4:00

$ qemu-virgil -enable-kvm -m 512 -device virtio-vga,virgl=on\
 -display sdl,gl=on -netdev user,id=ethernet.0,hostfwd=tcp::10022-:22\
 -device rtl8139,netdev=ethernet.0\
 -drive file=/snap/qemu-virgil/current/usr/share/qemu/edk2-x86_64-code.fd,if=pflash,format=raw,unit=0,readonly=on\
 ~/snap/qemu-virgil/common/ubuntu-core-20-amd64.img

This will create a QEMU window on your desktop and you need to follow through the prompts to initialise the VM with your launchpad account. (If you don’t have a launchpad account, you will need it to work with Ubuntu Core: get one and set up a public SSH key.)

Connect to the VP using ssh from a terminal window (ignore the address shown in the QEMU window and use the port set in the above command):

$ ssh -p 10022 <launchpad account>@localhost

Congratulations!

You should now have terminal access to your VM and a window containing a virtual display. You can install and run a variety of graphical snaps. You can stop the VM and restart it at any time using the same commands as in the last step.

Further reading

2 Likes
2

Unfortunately, I have been unable to get this to work.

qemu-virgil -enable-kvm -m 512 -device virtio-vga,virgl=on\
 -display sdl,gl=on -netdev user,id=ethernet.0,hostfwd=tcp::10022-:22\
 -device rtl8139,netdev=ethernet.0\
 -drive file=/snap/qemu-virgil/current/usr/share/qemu/edk2-x86_64-code.fd,if=pflash,format=raw,unit=0,readonly=on\
 ~/snap/qemu-virgil/common/ubuntu-core-20-amd64.img
WARNING: Image format was not specified for '/home/me/snap/qemu-virgil/common/ubuntu-core-20-amd64.img' and probing guessed raw.
         Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.
Could not access KVM kernel module: No such file or directory
qemu-system-x86_64: failed to initialize KVM: No such file or directory

All files specified in that command seem to be there

3

Did you connect the kvm snap interface as described above? And does your host machine have /dev/kvm ?

1 Like
4

Based on the above this is what I get:

sudo snap install qemu-virgil
qemu-virgil 4.2.0 from Oliver Grawert (ogra) installed

sudo snap connect qemu-virgil:kvm

qemu-virgil --version
QEMU emulator version 4.2.0 (v4.2.0-dirty)
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

So I guess kvm needs to be installed and configured. I was looking to create a VM under ESXi, but if that means creating it under kvm them exporting, I guess that’s what I’l have to do.

5

Well, are you running Ubuntu?

There is the kvm-ok script that should be shipped by default to check if kvm is supported by your hardware… you do/should not have to install anything, the kvm kernel module is a default of every Ubuntu kernel and should just auto-load when needed.

Could it be that virtualization is disabled in your BIOS/UEFI settings?

1 Like
6

Fresh copies of the Ubuntu server and desktop 22.04 running as a VM. ESXi supports nested virtualisation, so it should be no issue.

7

Urgh, you are right, the “Expose hardware assisted virtualization to the guest OS” was disabled within the VM. So that gets around the initial issue. Now I am seeing a permission denied issue.

sudo qemu-virgil -enable-kvm -m 512 -device virtio-vga,virgl=on -display sdl,gl=on -netdev user,id=ethernet.0,hostfwd=tcp::10022-:22 -device rtl8139,netdev=ethernet.0 -drive file=/snap/qemu-virgil/current/usr/share/qemu/edk2-x86_64-code.fd,if=pflash,format=raw,unit=0,readonly=on ~/snap/qemu-virgil/common/ubuntu-core-20-amd64.img
mkdir: cannot create directory '/run/user/0': Permission denied
qemu-system-x86_64: /home/me/snap/qemu-virgil/common/ubuntu-core-20-amd64.img: Could not open '/home/me/snap/qemu-virgil/common/ubuntu-core-20-amd64.img': Permission denied

Without sudo, a slightly differnt error, but ultimately still permission denied:

WARNING: Image format was not specified for '/home/me/snap/qemu-virgil/common/ubuntu-core-20-amd64.img' and probing guessed raw.
         Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.
Could not access KVM kernel module: Permission denied
qemu-system-x86_64: failed to initialize KVM: Permission denied
8

do you have a /dev/kvm and does lsmod | grep kvm return anything ?

9

Yes, /dev/kvm exists, and the output of lsmod | grep kvm is:

lsmod | grep kvm
kvm_intel             368640  0
kvm                  1028096  1 kvm_intel
10

Is the device in /dev owned by the kvm group and is your user in that group?

11

Hey @ogra, getting there…

You are correct in that my user was not part of the kvm group (which does own /dev/kvm with read/write permissions):

ls -l /dev/kvm
crw-rw----+ 1 root kvm 10, 232 Jan 19 02:30 /dev/kvm

groups me
me : me adm cdrom sudo dip plugdev kvm lpadmin lxd sambashare

However, adding the user to the group doesn’t resolve the issue - I still see the same permission errors when running qemu-virgil with in the user or sudo context.

12

you should not use sudo (that might mess up some things, i have never tested it in that context), try removing the snap with the --purge option set and then re-install it (dont forget to re-connect the kvm interface) … i.e.:

$ sudo snap remove --purge qemu-virgil
...
$ sudo snap install qemu-virgil
$ sudo snap connect qemu-virgil:kvm
...

also make sure the image has proper ownership and permissions for your user … if this does not work i fear i’m running out of ideas …

13

Tada :tada: Superstar. I have a console spinning up right now. Lets see what else I can break :slight_smile:

1 Like
14

Hi,

Tutorial starts with sudo snap install qemu-virgil…
Do we have to create a droplet (in DO, for example) first and then follow the tutorial?

Thanks.