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Ansible Role linuxfabrik.lfops.alternatives

This role manages symbolic links using the update-alternatives tool. Useful when multiple programs are installed but provide similar functionality (for example, different editors or Python interpreters).

Hints:

  • The priority is simply an integer weight that the system uses when you're in auto mode to choose which of several installed alternatives should be the current default.
  • When you install multiple candidates for the same generic name (e.g. python3), and you've left the alternative in auto mode, the one with the highest priority number will be selected.
  • When priorities are equal, the system will pick the first one that was registered (but you should avoid duplicate priorities to prevent ambiguity).

Available since LFOps 3.0.0.

How the Role Behaves

  • The role ensures the alternatives tooling is installed: the chkconfig package on RHEL 8, the alternatives package on RHEL 9 and 10. On Debian and Ubuntu, update-alternatives ships with dpkg, so nothing is installed there.
  • On Red Hat-family hosts link is mandatory for each entry. On Debian-based hosts it is only required when the alternative name is unknown to the system.
  • family is only available on Red Hat-family hosts (community.general 10.1.0+); subcommands requires community.general 5.1.0+. Both are passed through only when set, so they do not affect entries or platforms that do not use them.

Tags

alternatives

  • Installs the alternatives tooling and manages alternative programs for common commands.
  • Triggers: none.

Optional Role Variables

alternatives__alternatives

  • List of alternatives to remove or to deploy. With the default empty list, the role is a no-op.
  • Type: List of dictionaries.
  • Default: []

  • Subkeys:

    • name:

      • Mandatory. The generic name of the link.
      • Type: String.

    • family:

      • Optional. Groups similar alternatives. Red Hat-family only.
      • Type: String.

    • link:

      • The path to the symbolic link that should point to the real executable. This option is always required on RHEL-based distributions. On Debian-based distributions this option is required when the alternative name is unknown to the system.
      • Type: String.

    • path:

      • Optional. The path to the real executable that the link should point to.
      • Type: String.

    • priority:

      • Optional. The priority of the alternative. If no priority is given, the alternatives tool uses 50 as a fallback on creation.
      • Type: Number.

    • state:

      • Optional. One of: selected (default; install the alternative and set it as the currently selected alternative for the group), present (install the alternative but do not set it as the currently selected alternative for the group), auto (install the alternative and set the group to auto mode), absent (remove the alternative).
      • Type: String.
      • Default: 'selected'

    • subcommands:

      • Optional. Subcommands (also called slaves or followers) that are switched together with this alternative. Each entry needs name, link, and path.
      • Type: List of dictionaries.

Example:

alternatives__alternatives:
  # set the default python3, also switching its subcommands (slaves)
  - name: 'python3'
    link: '/usr/bin/python3'
    path: '/usr/bin/python3.12'
    priority: 100
    state: 'auto'
    subcommands:
      - name: 'python3-config'
        link: '/usr/bin/python3-config'
        path: '/usr/bin/python3.12-config'
  # Red Hat-family only: select an alternative by family
  - name: 'java'
    family: 'java-11-openjdk.x86_64'
  # remove an alternative
  - name: 'editor'
    path: '/usr/bin/vim'
    state: 'absent'

License

The Unlicense

Author Information

Linuxfabrik GmbH, Zurich