Creating a Virtual Wombat Image

Resources:

https://1xv447d.257.cz/posts/2022-04-29-raspbian-emulation-in-qemu

Raspberrry Pi OS Downloads:

https://www.raspberrypi.com/software/operating-systems/

https://downloads.raspberrypi.org/raspios_lite_arm64/images/raspios_lite_arm64-2022-09-07/2022-09-06-raspios-bullseye-arm64-lite.img.xz

Building the image from scratch:

1. Install QEMU system emulation binaries for ARM processors

sudo apt-get qemu-system-arm

2. Create new folder and put these downloads in it

mkdir Wombat-Bullseye

3. Download Pi Image with desktop and unzip to Wombat-Bullseye

4. Change image name to Wombat-Bullseye

mv 2022-09-06-raspios-bullseye-arm64-lite.img Wombat-Bullseye.img

5. Mount the partitions

sudo losetup --show --find --partscan Wombat-Bullseye.img

sudo mkdir /mnt/{raspbian-boot,raspbian-root}

sudo mount /dev/loop1p1 /mnt/raspbian-boot;
sudo mount /dev/loop1p2 /mnt/raspbian-root

6. Create a userconf.txt file and copy it to raspbian-boot (you can change the password and username if desired)

touch userconf.txt ;
echo -n 'kipr:' > userconf.txt ;
echo 'botball' | openssl passwd -6 -stdin >> userconf.txt

sudo cp userconf.txt /mnt/raspbian-boot/userconf.txt

7. Copy the kernel device tree file to Wombat-Bullseye

sudo cp /mnt/raspbian-boot/bcm2710-rpi-3-b.dtb .;
sudo cp /mnt/raspbian-boot/kernel8.img .

8. Unmount the image

sudo umount /dev/loop1p1;
sudo umount /dev/loop1p2;
sudo rmdir /mnt/{raspbian-boot,raspbian-root};
sudo losetup --detach /dev/loop1

9. Convert image to qcow2 format

qemu-img convert -f raw -O qcow2 Wombat-Bullseye.img Wombat-Bullseye.qcow2

10. Increase disk size to 8G (or whatever size your SD card is) using qemu-img
    • Warning: It may be a good idea to create a backup copy of the image before resizing it at this point

qemu-img resize Wombat-Bullseye.qcow2 8G

11. Create Wombat_Start.sh to run with correct dtb and kernel (or use the one in the repository)

#!/usr/bin/env bash
sudo qemu-system-aarch64 \
  -M raspi3b \
  -m 1024 \
  -kernel kernel8.img \
  -dtb bcm2710-rpi-3-b.dtb \
  -drive "format=qcow2,file=Wombat-Bullseye.qcow2" \
  -append "console=ttyAMA0 root=/dev/mmcblk0p2 rw rootwait rootfstype=ext4" \
  -device usb-net,netdev=net0 -netdev user,id=net0,hostfwd=tcp::5555-:22 \
  -serial stdio -usb -device usb-mouse -device usb-kbd

12. Run Wombat_Start.sh

./Wombat_Start.sh

13. After logging in enable ssh on bootup

sudo systemctl enable --now ssh.service

13. You can remain in this terminal or you can also connect locally

ssh kipr@127.0.0.1 -p 5555

14. Run fdisk to recreate the second partition

sudo fdisk /dev/mmcblk0

15. In fdisk, run these commands:

To show the current disk layout (note the starting sector of the second partition)

print

Delete the old partition 2

d
2

Create a new partition and make it the primary partition

n
p
2

Put in the starting sector of the old partition and enter to accept

xxxxx

Answer no to changing ext4 signature

n

Write all changes to disk and exit fdisk

w

16. Complete the resizing operation

sudo resize2fs /dev/mmcblk0p2

17. Confirm expanded disk size

df -h

18. Get updates now that there is enough space for them

sudo apt-get update

sudo apt-get upgrade