Configure instances with cloud-init¶

Automating routine system setup, such as network configuration and user account creation, cuts down on drudgery and ensures instances of your image are consistent. By embedding a cloud-init configuration into your image, you can automatically set up new instances whether they’re running in the cloud, a local virtual machine, or bare metal.

Set up cloud-init¶

First, install cloud-init in your image as an overlay package. This is best done by declaring a new part in your project file, similar to the following:

imagecraft.yaml¶

parts:
  packages:
    plugin: nil
    overlay-packages:
      # ...
      - cloud-init

Installing overlay packages

To install overlay packages, you must first install a package manager within the overlay file system, such as APT with the mmdebstrap plugin.

In the directory containing your project file, create a directory to hold the cloud-init configuration files:

mkdir cloud-init

In this directory, create a file named meta-data. This file configures cloud-init itself. In the file, paste the following content, replacing <id> with a meaningful identifier for your image:

cloud-init/meta-data¶

dsmode: local
instance_id: <id>

The dsmode key is set to local because the configuration is being sourced locally, not hosted on a network.

Declare which tasks to perform¶

Cloud-init sets up instances based on a file named user-data. The individual tasks performed during setup are determined by the modules declared in this file.

The cloud-config module reference contains a complete list of the available modules, with descriptions and examples for each. Using this reference, declare any modules necessary to set up your image.

The following example uses the Users and Groups and Set Passwords modules to create a new user account, change the default user’s password to default-pw, and require passwords to be reset when the user first logs in:

cloud-init/user-data¶

#cloud-config
users:
  - default
  - {name: user}
password: default-pw
chpasswd:
  expire: true
  users:
    - name: user
      password: passw0rd
      type: text

Once you’ve written the file, validate it by installing cloud-init onto your local machine and running the schema command:

sudo apt install cloud-init
cloud-init schema --config-file user-data --annotate

If any errors are listed in the output, resolve them before proceeding.

Copy cloud-init files¶

Copy the cloud-init files from your project directory to the image with a new part that uses the Dump plugin and the organize key. It should be processed after your root file system and system packages are in place.

In our example image, it’s written like this:

imagecraft.yaml¶

parts:
  cloud-init:
    after: [rootfs, packages]
    plugin: dump
    source: cloud-init/
    organize:
      "*": /var/lib/cloud/seed/nocloud/

Now, any instances created from your image will be set up identically.