Chapter 7. Configuring the discovery image

The Assisted Installer uses an initial image to run an agent that performs hardware and network validations before attempting to install OpenShift Container Platform. You can use Ignition to customize the discovery image.

Note

Modifications to the discovery image will not persist in the system.

7.1. Creating an Ignition configuration file

Ignition is a low-level system configuration utility, which is part of the temporary initial root filesystem, the initramfs. When Ignition runs on the first boot, it finds configuration data in the Ignition configuration file and applies it to the host before switch_root is called to pivot to the host’s root filesystem.

Ignition uses a JSON configuration specification file to represent the set of changes that occur on the first boot.

Important

Ignition versions newer than 3.2 are not supported, and will raise an error.

Procedure

  1. Create an Ignition file and specify the configuration specification version: 

    $ vim ~/ignition.conf
    {
  "ignition": { "version": "3.1.0" }
}

  2. Add configuration data to the Ignition file. For example, add a password to the core user.

    1. Generate a password hash: 

      $ openssl passwd -6

    2. Add the generated password hash to the core user: 

      {
  "ignition": { "version": "3.1.0" },
  "passwd": {
    "users": [
      {
        "name": "core",
        "passwordHash": "$6$spam$M5LGSMGyVD.9XOboxcwrsnwNdF4irpJdAWy.1Ry55syyUiUssIzIAHaOrUHr2zg6ruD8YNBPW9kW0H8EnKXyc1"
      }
    ]
  }
}

  3. Save the Ignition file and export it to the IGNITION_FILE variable: 

    $ export IGNITION_FILE=~/ignition.conf

7.2. Modifying the discovery image with Ignition

Once you create an Ignition configuration file, you can modify the discovery image by patching the infrastructure environment using the Assisted Installer API.

Prerequisites

  • If you used the UI to create the cluster, you have set up the API authentication.
  • You have an infrastructure environment and you have exported the infrastructure environment id to the INFRA_ENV_ID variable.
  • You have a valid Ignition file and have exported the file name as $IGNITION_FILE.

Procedure

  1. Create an ignition_config_override JSON object and redirect it to a file: 

    $ jq -n \
  --arg IGNITION "$(jq -c . $IGNITION_FILE)" \
  '{ignition_config_override: $IGNITION}' \
  > discovery_ignition.json

  2. Refresh the API token: 

    $ source refresh-token

  3. Patch the infrastructure environment: 

    $ curl \
  --header "Authorization: Bearer $API_TOKEN" \
  --header "Content-Type: application/json" \
  -XPATCH \
  -d @discovery_ignition.json \
  https://api.openshift.com/api/assisted-install/v2/infra-envs/$INFRA_ENV_ID | jq

    The ignition_config_override object references the Ignition file.

  4. Download the updated discovery image.