Container Image Requirements
============================

The CloudNativePG operator for Kubernetes is designed to work with any
compatible container image of PostgreSQL that complies with the
following requirements:

- PostgreSQL executables that must be in the path:

  - ``initdb``
  - ``postgres``
  - ``pg_ctl``
  - ``pg_controldata``
  - ``pg_basebackup``

- Barman Cloud executables that must be in the path:

  - ``barman-cloud-backup``
  - ``barman-cloud-backup-delete``
  - ``barman-cloud-backup-list``
  - ``barman-cloud-check-wal-archive``
  - ``barman-cloud-restore``
  - ``barman-cloud-wal-archive``
  - ``barman-cloud-wal-restore``

- PGAudit extension installed (optional - only if PGAudit is required in
  the deployed clusters)

- Appropriate locale settings

- ``du`` (optional, for ``kubectl cnpg status`` )

..  Important::
   Only  `PostgreSQL versions supported by the PGDG <https://postgresql.org/>`_  are allowed.

No entry point and/or command is required in the image definition, as
CloudNativePG overrides it with its instance manager.

..  Warning::
   Application Container Images will be used by CloudNativePG in a **Primary with multiple/optional Hot Standby Servers Architecture** only.

The CloudNativePG community provides and supports `public PostgreSQL container images <https://github.com/cloudnative-pg/postgres-containers>`_ 

that work with CloudNativePG, and publishes them on `ghcr.io <https://ghcr.io/cloudnative-pg/postgresql>`_  .

Image Tag Requirements
----------------------

To ensure the operator makes informed decisions, it must accurately
detect the PostgreSQL major version. This detection can occur in two
ways:

1. Utilizing the ``major`` field of the ``imageCatalogRef`` , if
   defined.

2. Auto-detecting the major version from the image tag of the
   ``imageName`` if not explicitly specified.

For auto-detection to work, the image tag must adhere to a specific
format. It should commence with a valid PostgreSQL major version number
(e.g., 15.6 or 16), optionally followed by a dot and the patch level.

Following this, the tag can include any character combination valid and
accepted in a Docker tag, preceded by a dot, an underscore, or a minus
sign.

Examples of accepted image tags:

- ``12.1``

- ``13.3.2.1-1``

- ``13.4``

- ``14``

- ``15.5-10``

- ``16.0``

..  Warning::
   `latest`  is not considered a valid tag for the image.

..  Note::
   Image tag requirements do no apply for images defined in a catalog.