# Backup/restore node instance

### Overview <a href="#overview" id="overview"></a>

This guide goes into detail on how to back up and restore a xBuildApp node instance. It covers the base folders and what they contain, as well as which files are critical for performing a successful backup and restore.

### Base folders <a href="#base-folders" id="base-folders"></a>

xBuildApp leverages LevelDB as its storage engine. When starting a xBuildApp node, the following sub-folders are created in the specified working directory:

* **blockchain** - Stores the blockchain data
* **trie** - Stores the Merkle tries (world state data)
* **keystore** - Stores private keys for the client. This includes the libp2p private key and the sealing/validator private key
* **consensus** - Stores any consensus information that the client might need while working. For now, it stores the node's *private validator key*

It is critical for these folders to be preserved in order for the xBuildApp instance to run smoothly.

### Create backup from a running node and restore for new node <a href="#create-backup-from-a-running-node-and-restore-for-new-node" id="create-backup-from-a-running-node-and-restore-for-new-node"></a>

This section guides you through creating archive data of the blockchain in a running node and restoring it in another instance.

**Backup**

`backup` command fetches blocks from a running node by gRPC and generates an archive file. If `--from` and `--to` are not given in the command, this command will fetch blocks from genesis to latest.

Copy

```
$ polygon-edge backup --grpc-address 127.0.0.1:9632 --out backup.dat [--from 0x0] [--to 0x100]
```

**Restore**

A server imports blocks from an archive at the start when starting with `--restore` flag. Please make sure that there is a key for new node. To find out more about importing or generating keys, visit the [Secret Managers section](https://dominicluu.gitbook.io/blockchaindocs/configuration/secret-managers).

Copy

```
$ polygon-edge server --restore archive.dat
```

### Back up/Restore Whole data <a href="#back-up-restore-whole-data" id="back-up-restore-whole-data"></a>

This section guides you through backup the data including state data and key and restoring into the new instance.

**Step 1: Stop the running client**

Since the xBuildApp uses **LevelDB** for data storage, the node needs to be stopped for the duration of the backup, as **LevelDB** doesn't allow for concurrent access to its database files.

Additionally, the xBuildApp also does data flushing on close.

The first step involves stopping the running client (either through a service manager or some other mechanism that sends a SIGINT signal to the process), so it can trigger 2 events while gracefully shutting down:

* Running data flush to disk
* Release of the DB files lock by LevelDB

**Step 2: Backup the directory**

Now that the client is not running, the data directory can be backed up to another medium. Keep in mind that the files with a `.key` extension contain the private key data that can be used to impersonate the current node, and they should never be shared with a third/unknown party.

:::info Please back up and restore the generated `genesis` file manually, so the restored node is fully operational. :::

### Restore <a href="#restore-1" id="restore-1"></a>

**Step 1: Stop the running client**

If any instance of the xBuildApp is running, it needs to be stopped in order for step 2 to be successful.

**Step 2: Copy the backed up data directory to the desired folder**

Once the client is not running, the data directory which was previously backed up can be copied over to the desired folder. Additionally, restore the previously copied `genesis` file.

**Step 3: Run the ZChains client while specifying the correct data directory**

In order for the Polygon Edge to use the restored data directory, at launch, the user needs to specify the path to the data directory. Please consult the [CLI Commands](https://dominicluu.gitbook.io/blockchaindocs/get-started/cli-command) section on information regarding the `data-dir` flag.