Build disk images with Elemental

Requirements:

• qemu-img utility
• elemental binary
• elemental runtime dependencies

The suggested approach is based on using the Elemental installer (elemental install command) to run the installation from a Linux to a loop device. The loop device can be a raw image created with qemu-img create that can easily be converted to other formats after the installation by using qemu-img convert.

Prepare the loop device

Preparing the a loop device for the installation is simple and straight forward.

# Create a raw image of 32G
> qemu-img create -f raw disk.img 32G

# Set the disk image as a loop device
> sudo losetup -f --show disk.img
<device>

Run elemental installation

Execute the elemental installation as described in installing:

> sudo elemental install --firmware efi --system.uri oci:<image=ref> <device>

Where <image-ref> is the Elemental derivative container image we want to use for the disk creation and <device> is the loop device previously created with losetup (e.g. /dev/loop0).

Convert the RAW image to desired format

Once the installation is done just unsetting the loop device and converting the image to the desired format is missing:

# Unset the loop device
> sudo losetup -d <device>

# Convert the RAW image to qcow2
> qemu-img convert -f raw -O qcow2 disk.img disk.qcow2

QEMU supports a wide range of formats including common ones such as vdi, vmdk or vhdx.

The result can be easily tested on QEMU with:

> qemu -m 4096 -hda disk.qcow2 -bios /usr/share/qemu/ovmf-x86_64.bin

Note the firmware image path varies depending on the host distro, the path provided in this example is based on openSUSE Leap.