Hetzner Debain ZFS image

Packer and Terraform scripts to create a reusable Hetzner cloud image that boots Debian on ZFS root.

• Usage
• How it works
• License

Usage

Create a local image

Requirements: Packer and VirtualBox.

$ cd image
$ make
...
$ ls debian.img
debian.img

The make command builds a raw disk image. Packer emulates key input to the virtual machine console to bootstrap installation, so do not touch mouse nor keyboard until packer sshs into the machine.

You may need to change livecd version in image/build.pkr.hcl to the latest release. Otherwise, packer fails to download the livecd iso because Debian project may delete old livecd images.

Tranfer to Hetzner cloud

Requirements: Terraform, curl and Hetzner Cloud API token.

$ cd snapshot
$ export HCLOUD_TOKEN=...
$ make
...
$ make clean

The make command spins up a rescue-mode CX11 instance on the Hetzner Cloud, sshs into the instance and transfers the image to the main disk of the instance. Then, it takes a snapshot of the image. You need to make clean yourself to destroy the server.

The size of the snapshot is ~900MB. The storage cost then is ~0.01 €/month.

Using the image

The image is labeled with image=debian-11-zfs. You may want to use this label to select the image in a Terraform configuration.

The image forbids root login and password authentication. You should supply the following cloudinit configuration or similar to the instance as a user data:

#cloud-config

timezone: UTC

system_info:
  default_user:
    name: hetzner
    shell: /bin/bash
    sudo: "ALL=(ALL) NOPASSWD: ALL"

This will create non-root user hetzner. Public keys will be injected to this user. You will see ZFS dataset in the created instance:

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            958M     0  958M   0% /dev
tmpfs           195M  3.0M  192M   2% /run
main/debian      37G  752M   36G   3% /
tmpfs           974M     0  974M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           974M     0  974M   0% /sys/fs/cgroup
/dev/sda2       488M   49M  404M  11% /boot
$ sudo zfs list
NAME          USED  AVAIL     REFER  MOUNTPOINT
main          753M  35.7G       96K  none
main/debian   752M  35.7G      752M  /

How it works

The packer script installs Debian root-on-zfs to a local virtual machine by chrooting from a livecd shell. The Makefile uses vbox-img to convert virtual hard disk to raw disk image. Then, snapshot scripts boot a rescue linux system on a cloud instance and write the disk image directly to the instance main disk. The snapshot of the instance then works as a Debian ZFS image.

Booting an instace based on the created image runs first-boot sequence including cloud-init, which automatically configures the system just like other official images (including the auto-configured root password and injected SSH pubkeys).

License

MIT license.