Backup and restore instructions for nonce files (#543)

* Backup and restore instructions for nonce files

* Baker stores data in client folder

Co-authored-by: Germán Delbianco <[email protected]>

* grammar

* legacy baking deployments

Co-authored-by: Germán Delbianco <[email protected]>

* Examples of file names

* One cycle

* Deployments

---------

Co-authored-by: Germán Delbianco <[email protected]>

Author: timothymcmackin

docs/tutorials/join-dal-baker/run-baker.md

@@ -124,6 +124,15 @@ However, make sure not to run the baker twice **for the same protocol version an
 
 You can upgrade accusers with a similar process.
 
+## Backing up and restoring the baker
+
+The Octez baking daemon stores persistent operational data in the Octez client's data directory, notably consensus high-water marks and [random seed nonces](https://tezos.gitlab.io/active/randomness_generation.html).
+If you want to back up the baker or move it to another machine and restore it, you must copy the nonce file or files from the Octez client's data directory to the equivalent directory on the new machine.
+These nonce files are named `net<NETWORK_ID>_stateful_nonces` and `net<NETWORK_ID>_nonces`, where `<NETWORK_ID>` is the ID of the network, such as `netXdQprcVkpaWU_stateful_nonces` for Mainnet or `netXnHfVqm9ie_stateful_nonces` for Ghostnet.
+All deployments have the `net<NETWORK_ID>_stateful_nonces` file but only legacy baking deployments running versions of Octez prior to 20.0rc1 have the `net<NETWORK_ID>_nonces` file.
+
+After you have moved the nonce files to the new machine and verified that the baker runs normally for one cycle, you can remove the legacy `net<NETWORK_ID>_nonces` file.
+
 ## Calculating the delay for attestation rights
 
 If you are setting up a new baker, you must wait until it receives attestation rights before it can bake blocks or attest to DAL data.