Building from scratch machines with similar configuration is not very wise. Unless it’s not often. Preparing at least LXD base images would be helpful. Small routine tasks like changing the default repositories, MOTD, adding ssh keys and base tools would take more than 5 minutes per machine. 5 new machines per week, that takes a lot. To be effective, system administrators should be lazy and rational.

Packer from Hashi corp is really good tool for building immutable infrastructure. It supports building of different images for the cloud, on-premise environments and desktop hypervisors simultaneously.

LXD is a hypervisor for Linux containers and virtual machines (since version 4.0). The containers in LXD are stateful. This means that their files are persistent compared to Docker where storage mounts are necessary. Also, the LXD containers are most likely full system virtualization. They run a full bootstrapped operating system userspace with the init system. The key difference between LXD and LXC is that LXD is a hypervisor for LXC containers and KVM virtual machines. LXD is based on liblxc and contains REST api.

I won’t cover the initial configuration of LXD in this post. Packer is written in GoLang and it’s a single binary. It could be downloaded in arhive from the official download page. Alternatively, it can also be installed with homebrew. The binary could be put in /usr/local/bin or in another directory of the working machine which is in the PATH.

The Ansible provisioner is still not compatible with the LXD builder module. There is a known bug, it hangs on “collecting artifacts” ( #PACKER-9034 ). Ansible is not getting the correct IP of the container from Packer and it’s stuck on trying to connect with SSH.

A workaround is using the ansible-local provisioner. The difference is that the Ansible runs locally inside the container. It must be installed in advance with the shell provisioner. Now it’s not necessary to copy the playbook inside the container with file provisioner. ansible-local provisioner does it automatically and creates a temporary directory.

Example Packer json (lxd-ansible-local.json):

{
  "provisioners": [
    {
      "type": "shell",
      "inline": "[ \"$(ansible --version > /dev/null && echo ok)\" != 'ok' ] && apt update && apt -y install ansible || echo 'ansible already installed.'"
    },
    {
      "type": "ansible-local",
      "playbook_file": "./playbook/example-playbook.yml",
      "playbook_dir" : "./playbook"
    }
  ],


  "builders": [
    {
      "type": "lxd",
      "name": "acme-focal",
      "image": "ubuntu-daily:focal",
      "output_image": "acme_ubuntu-focal",
      "init_sleep": "10",
      "publish_properties": {
        "description": "Focal image by ACME corp."
      }
    }
  ]
}

Here we have the shell provisioner which is installing Ansible with bash one-liner.

"playbook_file": "./playbook/example-playbook.yml" - The exact name of the playbook file to be executed;

"playbook_dir" : "./playbook" - The playbook directory to be copied to the container. Have a look at the roles config in the playbook file below!;

"name": "acme-focal" - Name of the started temporary container and name of the task for logging;

"image": "ubuntu-daily:focal" - Our image is based on ubuntu-daily:focal ;

"output_image": "acme_ubuntu-focal" - The name of our new image;

"init_sleep": "10" - Seconds to sleep between launching the container and provisioning it. My DNS is slow. That’s why the value is high.

Example playbook (./playbook/example-playbook.yml):

---

  - hosts: 127.0.0.1
    connection: local
    roles:
      - playbook/roles/acme-firstfive

There is nothing special here. Only the roles path is important. Packer is copying this file to the root working directory. That’s why the exact path to the role must be specified, including the playbook dir.

connection: local parameter is used with 127.0.0.1 for host.

The whole file tree is published here as example project.

Building

To build the project, simply run:

git clone https://code.petrovs.info/blago/packer-lxd-demo.git && cd packer-lxd-demo

packer build lxd-ansible-local.json

The temporary container is deleted immediately after deployment and only the image is published. To keep the container running for debugging in case of failure, use the option -on-error=abort:

packer build -on-error=abort lxd-ansible-local.json

Note that it may look like paused if the base image is downloading from the remote repository. It’s fine, just wait some more minutes. Depends of the image size. “Unpacking Ansible” with apt is also slow.

Let’s have a look at the demo:

To be done

I didn’t try the option to build LXD VM image. It should work the same way. For virtualization, the --vm option is passed with lxd launch. Probably it must be implemented in Packer unless there is an option for command line arguments to lxc. LXD VM’s use the same format and repositories as the container images. The only difference is that they are compressed qcow’s. LXD virtualization is a topic for another post.

There is no option for choosing LXD profiles in Packer. It’s an important feature. For example, in my home setup, lxd launch must receive profiles for networking and storage. There are different networks and the default configuration won’t boot.

Already mentioned, the Ansible provisioner currently doesn’t work with the LXD provisioner but Ansible-local is a workaround.

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