Monday, May 9, 2016

Booting ubuntu 16.04 cloud images on Arm64

For testing kvm/qemu, prebaked images cloud images are nice. However, there is a few steps to get started. First we need a recent Qemu (2.5 is good enough). An efi firmware is needed, and cloud-utils, for customizing our VM.
sudo apt install -y qemu qemu-utils cloud-utils
wget https://releases.linaro.org/components/kernel/uefi-linaro/15.12/release/qemu64/QEMU_EFI.fd
wget https://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-arm64-uefi1.img
Cloud images are plain - there is no user setup, no default user/pw combo, so to log in to the image, we need to customize the image on first boot. The defacto tool for this is cloud-init. The simplest method for using cloud-init is passing a block media with a settings file - of course for real cloud deployment, you would use one of fancy network based initialization protocols cloud-init supports. Enter the following to a file, say cloud.txt:
#cloud-config

users:
  - name: you
    ssh-authorized-keys:
      - ssh-rsa AAAAB3Nz....
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    groups: sudo
    shell: /bin/bash
This minimal config will just set you a user with ssh key. A more complex setup can install packages, write files and run arbitrary commands on first boot. In professional setups, you would most likely end up using cloud-init only to start Ansible or another configuration management tool.
cloud-localds cloud.img cloud.txt
qemu-system-aarch64 -smp 2 -m 1024 -M virt -bios QEMU_EFI.fd -nographic \
       -device virtio-blk-device,drive=image \
       -drive if=none,id=image,file=xenial-server-cloudimg-arm64-uefi1.img \
       -device virtio-blk-device,drive=cloud \
       -drive if=none,id=cloud,file=cloud.img \
       -netdev user,id=user0 -device virtio-net-device,netdev=user0 -redir tcp:2222::22 \
       -enable-kvm -cpu host 
If you are on an X86 host and want to use qemu to run an aarch64 image, replace the last line with "-cpu cortex-a57". Now, since the example uses user networking with tcp port redirect, you can ssh into the VM:
ssh -p 2222 you@localhost
Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-22-generic aarch64)
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