Build an Ubuntu Server live image with mkosi

Basic Config

[Distribution]
Distribution=ubuntu

[Output]
Format=disk

[Content]
Packages=
    apt
    cloud-init
    dbus
    grub-efi-amd64-signed
    iproute2
    linux-virtual
    netplan.io
    openssh-server
    openssl
    shim-signed
    ssh-import-id
    sudo
    systemd
    systemd-resolved
    udev
    vim
Bootloader=grub
ShimBootloader=signed
BiosBootloader=none
Bootable=true
RootPassword=ubuntu
KernelCommandLine=console=ttyS0
Hostname=ubuntu

Then simply run mkosi.

Boot the image

Use this script (use –no-snapshot to make the changes persist):

./start-vm.sh ./image.raw

To go further

At the moment, mkosi only supports producing raw disk images. To convert the image to qcow2:

qemu-img convert -f raw -O qcow2 /tmp/image.raw /tmp/ubuntu.img

And to make it (virtually) bigger:

qemu-img resize /tmp/ubuntu-24.04.img +50G