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How to add third party RPMs at install time​

This example is covering the case in which extra RPMS (e.g. specific hardware drivers) are included into the ISO and during the installation they are installed over the OS image.

For that use case the following files are required:

  • additional RPMs to install
  • additional cloud-config file defining hooks to copy and install binaries as installation hooks

We can handle it all into a single SeedImage.spec.cloud-config section assuming the additional RPM is available to download it from a remote server at installation time.

Consider the following cloud-config data which could be used as the content of the cloud-config section in a SeedImage resource.

name: "Install extra drivers"
stages:
  before-install:
  # Preload data to the persistent storage
  # During installation persistent partition is mounted at /run/elemental/persistent
  - downloads:
    - path: /tmp/some_package.rpm
      url: "<REMOTE_PACKAGE_URL>"
      permissions: 0777
  - commands:
    - mkdir -o /run/elemental/persistent/extra-pkgs
    - cp -p /tmp/some_package.rpm /run/elemental/persistent/extra-pkgs

  after-install-chroot:
  # Install the package at install time
  - commands:
    - rpm -iv /run/elemental/extra-pkgs/some_package.rpm

  # Include to the install system analog upgrade and reset hooks
  - files:
    - path: /oem/extra-pkg.yaml
      permissions: 0664
      content: |
        name: "Install extra drivers"
        stages:
          after-upgrade-chroot:
          # Install the package after upgrading to a new image
          - commands:
            - rpm -iv /run/elemental/extra-pkgs/some_package.rpm
          after-reset-chroot:
          # Install the package on reset
          - commands:
            - rpm -iv /run/elemental/extra-pkgs/some_package.rpm

Note the installation hooks only cover installation procedures, so that additional cloud-config data should be also part of the installed system in order to keep installing the package as part of the upgrade or reset processes.

Repacking a generated ISO image with extra files​

Alternatively, if having the dynamic download of content at install time is not a desired behavior and an ISO already including all the extra binaries is the actual goal this can is also possible but requires manually repacking the ISO.

Using xorriso, the linux utility to create ISOs, this turns to be a relatively easy process.

Let's create an overlay directory to create the directory tree that needs to be added into the ISO root. In that case the overlay directory could contain:

overlay/
  data/
    extra-pkgs/
      some_package.rpm
  iso-config/
    install_hooks.yaml

We are assuming the install_hooks.yaml is the content the actual cloud-config exposed in the previous section which is manually included into image instead of being embedded in a SeedImage resource. The data folder is eventually including the binaries we want to append into the ISO.

Assuming we already downloaded an Elemental ISO tied to a specific MachineRegistration with the following xorriso call all the overlay folder contents would be included into a new ISO:

xorriso -indev elemental.x86_64.iso -outdev elemental.custom.x86_64.iso -map overlay / -boot_image any replay

Requires xorriso equal or higher than version 1.5.

The contents of install_hooks.yaml could eventually be the same as the previous section but omiting the RPM package download and also adapting the RPM path to /run/initramfs/live/data/extra-pkgs/some_package.rpm as the ISO root folder is mounted at /run/initramfs/live.