docs: Document wal-g restore process.

docs/production/export-and-import.md

@@ -587,6 +587,53 @@ analysis of recent application-level data changes.
 You may also want to adjust the [incremental backups][incremental]
 configuration.
 
+### Restoring from wal-g backups
+
+The following steps will restore the database from the latest
+backup. Note that this process will _delete your current database_.
+
+1. As `root` on your database host, check your list of backups; the
+   most recent will be listed at the bottom, and is what will be
+   restored by the commands below.
+
+   ```shell
+   env-wal-g backup-list --pretty
+   ```
+
+1. Stop Zulip, if it is running. On your application host (which may
+   or may not be different from your database host, depending on your
+   configuration):
+
+   ```shell
+   /home/zulip/deployments/current/scripts/stop-server
+   ```
+
+1. As `root` on your database host, stop PostgreSQL:
+
+   ```shell
+   service postgresql stop
+   ```
+
+1. As `root` on your database host, delete the current database, and
+   restore from the backup. This may take some time, depending on the
+   size of your database and your connection to your backup storage.
+
+   ```shell
+   pg_version=$(crudini --get /etc/zulip/zulip.conf postgresql version)
+   rm -rf "/var/lib/postgresql/$pg_version/main"
+   env-wal-g backup-fetch "/var/lib/postgresql/$pg_version/main" LATEST
+   chown -R postgres.postgres "/var/lib/postgresql/$pg_version/main"
+   touch "/var/lib/postgresql/$pg_version/main/recovery.signal"
+   service postgresql start
+   ```
+
+1. As `root` on your application host, flush caches and start Zulip:
+
+   ```shell
+   /home/zulip/deployments/current/scripts/setup/flush-memcached
+   /home/zulip/deployments/current/scripts/start-server
+   ```
+
 [wal]: https://www.postgresql.org/docs/current/wal-intro.html
 [archive-timeout]: https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-ARCHIVE-TIMEOUT
 [mobile-push]: ../production/mobile-push-notifications.md