consul/website/content/docs/agent/wal-logstore/migrate-to-wal.mdx

---
layout: docs
page_title: Migrate to WAL with an existing BoltDB database
description: >-
Learn how to migrate from boltDB to WAL with an existing boltDB database.
---

# Migrate to WAL with an existing BoltDB database

This topic describes how to migrate to WAL with an existing boltDB database.

The overall process for migrating to WAL with an existing BoltDB database, this take assume that you have a cluster of at least 3 servers:

1. Stop target server gracefully.
1. Remove data directory from target server.
1. Update target server's configuration to set wal as raft_logstore backend.
1. Start target server.

## Stop target server gracefully

Stop the target server gracefully. For example, if you are using `systemd`,
run the following command:

```shell-session
$ systemctl stop consul
```

If your environment uses configuration management automation that might interfere with this process, such as Chef or Puppet, you must disable them until you have completely reverted the storage backend.

## Remove data directory from target server

Temporarily moving the data directory to a different location is less destructive than deleting it. We recommend moving the data directory instead of deleted it in cases where you unsuccessfully enable WAL. Do not use the old data directory (`/data-dir/raft.bak`) for recovery after restarting the server. We recommend eventually deleting the old directory.

The following example assumes the `data_dir` in the server's configuration is `/data-dir` and renames it to `/data-dir.bolt.bak`.

```shell-session
$ mv /data-dir/raft /data-dir/raft.bolt.bak
```

When switching backend, you must always remove _the entire raft directory_ not just the `raft.db` file or `wal` directory. This is because the log must always be consistent with the snapshots to avoid undefined behavior or data loss.

## Update target server's configuration

Modify the `backend` in the target server's configuration file:

```hcl
raft_logstore {
  backend = "wal"
  verification {
    enabled = true
    interval = "60s"
  }
}
```

## Start target server

Start the target server. For example, if you are using `systemd`, run the following command:

```shell-session
$ systemctl start consul
```

Watch for the server to become a healthy voter again.

```shell-session
$ consul operator raft list-peers
```

### Clean up old data directories

If necessary, clean up any `raft.bolt.bak` directories. Replace `/data-dir` with the value you specified in your configuration file.

```shell-session
$ rm /data-dir/raft.bak
```