How to load and generate data required before the Pod startup?

Init containers run and complete successfully before any application containers in a Pod start, making them perfect for pre-initialization tasks like loading data, which can then be shared with the main application containers via a shared volume.

A PVC (Persistent Volume Claim) provides persistent storage for a Pod but doesn't inherently define how data is loaded into it before application startup, just that it's available.

A sidecar container runs alongside the main application container, not before it, so it cannot ensure data is present before the main application starts.

Using another Pod with a PVC would run independently and wouldn't directly ensure data is loaded into the *current* Pod's volume before its startup, as init containers do.