A container running as a non-root user fails to write to a mounted volume with a permission denied error.

The volume's host-side directory (or the data already inside a named volume) is likely owned by a UID that doesn't match the non-root user's UID inside the container. Fix by aligning UIDs explicitly (e.g., creating the container's user with a specific UID matching the host directory's ownership, or using an init container/entrypoint step that `chown`s the mount path to the correct UID before the main process starts).