Set restic destination chunker parameters before copying snapshots

Choose destination chunking parameters before transferring a restic snapshot history.

Source facts

Restic’s repository guide warns that cross-repository snapshot copying reads and uploads the selected content because repositories use different encryption keys. Different chunker parameters can prevent deduplication of content already represented there. A new destination can be initialized with the source repository’s chunker parameters using the documented copy-chunker-params option. Those parameters cannot be changed after the destination repository exists. Copying snapshots therefore involves an initialization decision as well as a choice of snapshots and credentials.

Source: restic — Working with Repositories.

Applicability

This applies to the stable restic cross-repository copy procedure. It addresses deduplication compatibility and initialization, not a claim that repository passwords or encryption keys should be shared.

DSE recommendation

DSE recommends deciding the destination’s intended role before initializing it: independent recovery copy, consolidation target, or migration destination. Record whether source chunker parameters should be preserved and confirm the choice before transferring a large history. Keep encryption-key custody and access permissions separately governed. Plan temporary and final destination capacity using observed trial results rather than assuming copied snapshots will occupy no additional space. Preserve the source repository until the destination recovery path has been reviewed.

Verification

Create disposable source and destination repositories with the proposed initialization options. Copy selected snapshots, inspect destination statistics, and restore representative files from the destination independently. Retain the chosen parameters and observations so the final migration decision rests on measured behavior rather than an assumed deduplication ratio.

Official reference

restic — Working with Repositories. Reviewed October 15, 2026.