Running ARM64 Debian 11 on macOS via qemu

Many times, it is desirable to have access to Linux (ARM64) on a Mac. For example, we can build software for the Raspberry Pi, faster than building on the Pi itself.

The first guide I found was the one on Debian wiki. The advantage is that there is no need to spend time installing Debian but only Debian 9 and 10 are available.

Then I found this instruction that allows us to install latest Debian and felt like easier to make it work on macOS. I couldn't be so wrong: compiling libguestfs is truly a pain on macOS.

Both method depends on one crucial thing: access to files in the qcow2 disk image file.

Here is the smart part: I don't have to run the extraction on my own macOS machine. So yeah, upload the 1.5GB qcow2 file to Google Linux VM on the cloud and use nbd method in the previous guide. Good thing is that we only need to do this once because once our Debian machine is up and running, we have access to Linux locally without reliance on Google!

Download mini.iso, debian-installer/arm64/linux and debian-installer/arm64/initrd.gz.

Create disk image and install Debian

export DEBIAN_VM_IMAGE_NAME=debian11-5.10.0-18-arm64.qcow2

qemu-img create -f qcow2 $DEBIAN_VM_IMAGE_NAME 32G

qemu-system-aarch64 -M virt -cpu cortex-a53 -m 1G -kernel ./linux -initrd ./initrd.gz \
    -hda $DEBIAN_VM_IMAGE_NAME -append "console=ttyAMA0" \
    -drive file=mini.iso,id=cdrom,if=none,media=cdrom \
    -device virtio-scsi-device -device scsi-cd,drive=cdrom -nographic

Once installation completes, turn off the virtual machine by killing the terminal. (Can't Ctrl+C here!)

Keep a compressed copy of the disk image just in case as well as save uploading time in the next step

xz -9 -k $DEBIAN_VM_IMAGE_NAME

Upload the compressed disk image to a Linux machine and decompress it. Then we can extract the kernel and initrd from it by

sudo apt-get install qemu-utils qemu-efi-aarch64 qemu-system-arm
sudo modprobe nbd
sudo qemu-nbd -c /dev/nbd0 $DEBIAN_VM_IMAGE_NAME
sudo mount /dev/nbd0p2 /mnt

cp /mnt/boot/initrd.img-* ~
cp /mnt/boot/vmlinuz-* ~

sudo umount /mnt
sudo qemu-nbd -d /dev/nbd0

Note: In the 4th command, nbd0p2 might be nbd0p1 if you choose to have only one partition during installation.

Copy the two files back to your Mac.

Now we can launch the virtual machine with
```
qemu-system-aarch64 -M virt -cpu cortex-a53 -m 1G -initrd initrd.img-5.10.0-18-arm64 \
    -kernel vmlinuz-5.10.0-18-arm64 -append "root=/dev/vda2 console=ttyAMA0" \
    -drive if=virtio,file=$DEBIAN_VM_IMAGE_NAME,format=qcow2,id=hd \
    -net user,hostfwd=tcp::10022-:22 -net nic \
    -device intel-hda -device hda-duplex -nographic
```
Note:
- /dev/vda2 could be /dev/vda1 in case you have only one partition.
- On M1 Macs, change the CPU to -cpu max and add -accel hvf and possibly increase the memory to 2G to achieve near native performance.
For convenience, we have the script start_vm.sh to avoid typing/copying the above long command. Change it appropriately before use.

You can now SSH into the machine

ssh -Y $YOUR_VM_USER_NAME@localhost -p 10022

To shutdown the VM cleanly, switch to root (su) and then execute
```
/sbin/shutdown -P 0
```
or sudo but you will have to set it up first.

Other things

This SO question leads to this post which gives another guide to get Ubuntu running which do not need access to files in qcow2 image so no Linux access is needed.
See this to understand more about the internal of qemu.
Our script build_qemu.sh builds qemu on macOS if you do not want to use homebrew.

light-tech / Debian-on-macOS

Running ARM64 Debian 11 on macOS via qemu

Other things

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