To create an image for a Raspberry Pi, you generally have two main scenarios:

1. Starting fresh with a new OS (e.g., Raspberry Pi OS, Ubuntu, Home Assistant OS).
2. Cloning or backing up your existing Pi setup into a custom image.

Here, I'll explain the first method. The steps are:

1. Download your desired OS image
   • Go to the Raspberry Pi OS download page or your preferred OS site.
   • Download the .img or .zip file.
2. Write the image to a microSD card
   • Install Raspberry Pi Imager.
   • Select your OS, your SD card, and click Write.
   • Alternatively, use balenaEtcher or the dd command (Linux/macOS).
3. Configure before first boot (optional)
   • After writing, open the SD card’s boot partition.
   • Create an empty file named ssh to enable SSH.
   • Edit wpa_supplicant.conf to preconfigure Wi-Fi.

Making a Smaller, Distributable Image (Optional)

If your SD card is big but you don’t need all that empty space:

• Use PiShrink to shrink .img files so they only take up as much space as actual data.

Now, such an image would not run in Virtual Box, because VirtualBox expects disk formats like VDI, VHD, or VMDK. But you can convert img files to vdi, and back.

To convert img to vdi:

VBoxManage convertfromraw my-raspi.img my-raspi.vdi --format VDI

You could also use --format VMDK for VMware compatibility.

and to convert a vdi file to img, use this command:

VBoxManage clonemedium disk mydisk.vdi mydisk.img --format RAW

Alternatively, you can use qemu like so:

qemu-img convert -f vdi -O raw mydisk.vdi mydisk.img

.