### Migrate Backblaze B2 S3 bucket: Public media library

Move object storage from Backblaze B2 S3 bucket to Ample, one component at a time. Destination verified on Ample: an object written to a published bucket with an immutable Cache-Control header, a mapping row, and the CDN URL serving it publicly. Source procedure: Inventory the bucket with `rclone size` or the B2 dashboard. Not migrated automatically: B2 file versions, lifecycle rules and application-key restrictions are not migrated. Cutover: Switch the app's S3_* environment to the Ample bucket with a redeploy, verify reads and writes, keep B2 read-only until confirmed. Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

#### Workload

- Public media library

#### Migration Source

- Backblaze B2 S3 bucket

#### Prerequisites

1. Authorized access to the Backblaze B2 S3 bucket source and its export tooling
2. An inventory of every component in scope and out of scope
3. A validated backup or copy before any cutover
4. An Ample account token with servers:write, buckets:write

#### Resource Requirements

- S3-compatible object storage

#### Migration Steps

1. **Inventory the source**  
   List what Backblaze B2 S3 bucket provides beyond the component you are moving. Out of scope here: B2 file versions, lifecycle rules and application-key restrictions are not migrated.

2. **Source step 1**  
   Inventory the bucket with `rclone size` or the B2 dashboard.

3. **Source step 2**  
   Copy objects with `rclone sync` from the B2 S3-compatible endpoint to the Ample bucket endpoint using the issued credentials (path-style).

4. **Source step 3**  
   Verify a sample of objects by size and checksum after the copy.

5. **Create the destination bucket and copy**  
   Create the bucket, copy with rclone or the S3 CLI in path-style mode using the issued credentials, then pass the credentials to the app as encrypted S3_* variables.

```bash
   ample bucket create --name 
   ```

6. **Validate before cutover**  
   Run the app's own checks and, for data, compare counts and checksums; the example checks are the pattern self-tests (/p/public-media-library).

7. **Cut over**  
   Switch the app's S3_* environment to the Ample bucket with a redeploy, verify reads and writes, keep B2 read-only until confirmed.

8. **Rollback**  
   Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

#### Limitations

- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from Backblaze B2 S3 bucket's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- No full source-product parity is claimed: B2 file versions, lifecycle rules and application-key restrictions are not migrated.

#### Success Checks

1. Destination app responds on its public URL (`/`) expecting `ample canary express patterns`.
2. Public-media-library check from the destination example.
3. Data or object counts and checksums match the source.