Simulating Alpine Linux provisioning

README.md

Simulating how Alpine Linux boots at VPS provider

Steps to create the guest

1. Get a pristine image of the Alpine Linux 3.19 disk with cloud-init support.

   wget https://dl-cdn.alpinelinux.org/alpine/v3.19/releases/x86_64/alpine-virt-3.19.6-x86_64.iso

2. Add your SSH keys to user-data. You can find your SSH keys with:

   ssh-add -L

   Copy them into the lines of ssh-rsa ... in user-data below.

3. Create your own user-data file. Example is in another file in this gist. Also create a meta-data file:

   echo "hostname: my-test-infra" > meta-data

4. Run the libvirt installer

   virt-install --connect qemu:///session \
     --osinfo alpinelinux3.19 \
     --name my-test-infra \
     --network user \
     --location alpine-virt-3.19.6-x86_64.iso,kernel=boot/vmlinuz-virt,initrd=boot/initramfs-virt \
     --extra-args console=ttyS0 \
     --graphics none \
     --console pty,target_type=serial \
     --cloud-init meta-data=meta-data,user-data=user-data \
     --noreboot

To access the guest from your host

1. Start the guest:

   virsh --connect qemu:///session start my-test-infra

2. Run a QEMU monitor command to forward the port.

   virsh --connect qemu:///session qemu-monitor-command my-test-infra --hmp --cmd "hostfwd_add tcp::2222-:22"

3. SSH to the VM without saving the keys (you will keep rebuilding this host to test, right?)

   ssh localhost -l root -p 2222 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no

Get rid of the guest

1. Destroy the running instance

   virsh --connect qemu:///session destroy my-test-infra

2. Undefine the guest

   virsh --connect qemu:///session undefine my-test-infra --storage vda

user-data

#alpine-config

ssh_authorized_keys:
  - ssh-rsa AAA...
  - ecdsa-sha2-nistp256 AAA..

apk:
  repositories:
    - base_url: https://dl-cdn.alpinelinux.org/alpine
      repos:
        - main
        - community

packages:
  - python3

runcmd:
  - rm /etc/runlevels/*/tiny-cloud*

  - mkdir /root/.ssh
  - cp /home/alpine/.ssh/authorized_keys /root/.ssh
  - chmod 700 /root/.ssh
  - chmod 600 /root/.ssh/authorized_keys
  - lbu include /root/.ssh /home/alpine/.ssh

  - ERASE_DISKS=/dev/vda setup-disk -m sys /dev/vda

  - mount /dev/vda3 /mnt
  - mount /dev/vda1 /mnt/boot
  - sed -i 's/quiet/console=ttyS0/g' /mnt/etc/update-extlinux.conf
  - sed -i 's/^serial_port=/serial_port=0/g' /mnt/etc/update-extlinux.conf
  - chroot /mnt update-extlinux
  - chroot /mnt rc-update add networking

  - poweroff