This guide covers the manual steps required to upgrade PostgreSQL across a major version when using the CloudNativePG (CNPG) operator-based PostgreSQL installation — i.e., when PostgreSQL is managed through the experimental postgresql-operator and postgresql-cluster rather than through the Release CR's built-in spec.postgresql keys.
PostgreSQL cannot be automatically upgraded during an operator-to-operator or Helm-to-operator upgrade due to incompatible data formats between different PostgreSQL server versions. In such cases, a manual upgrade is necessary. The process involves first backing up the PostgreSQL data, then upgrading to the new PostgreSQL version, and finally restoring the data in the upgraded version.
This guide covers the manual steps required to migrate from the Bitnami chart-managed PostgreSQL installation (the default up to and including operator 25.1 releases) to the CloudNativePG (CNPG) operator-managed equivalent introduced in operator 25.3 releases.