The cluster restoration program is implemented as a separate command-line utility ndb_restore, which can normally be found in the MySQL bin directory. This program reads the files created as a result of the backup and inserts the stored information into the database.

ndb_restore must be executed once for each of the backup files that were created by the START BACKUP command used to create the backup (see Section 15.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup”). This is equal to the number of data nodes in the cluster at the time that the backup was created.

The following table includes command options specific to the MySQL Cluster native backup restoration program ndb_restore. Additional descriptions follow the table. For options common to all MySQL Cluster programs, see Section 15.4.21, “Options Common to MySQL Cluster Programs”.

Typical options for this utility are shown here:

ndb_restore [-c connectstring] -n node_id [-m] -b backup_id -r [backup_path=]/path/to/backup/files

The -c option is used to specify a connectstring which tells ndb_restore where to locate the cluster management server. (See Section 15.3.2.2, “The MySQL Cluster Connectstring”, for information on connectstrings.) If this option is not used, then ndb_restore attempts to connect to a management server on localhost:1186. This utility acts as a cluster API node, and so requires a free connection “slot” to connect to the cluster management server. This means that there must be at least one [api] or [mysqld] section that can be used by it in the cluster config.ini file. It is a good idea to keep at least one empty [api] or [mysqld] section in config.ini that is not being used for a MySQL server or other application for this reason (see Section 15.3.2.6, “Defining SQL and Other API Nodes in a MySQL Cluster”).

You can verify that ndb_restore is connected to the cluster by using the SHOW command in the ndb_mgm management client. You can also accomplish this from a system shell, as shown here:

shell> ndb_mgm -e "SHOW"

-n is used to specify the node ID of the data node on which the backups were taken.

The first time you run the ndb_restore restoration program, you also need to restore the metadata. In other words, you must re-create the database tables — this can be done by running it with the -m option. Note that the cluster should have an empty database when starting to restore a backup. (In other words, you should start ndbd with --initial prior to performing the restore.)

The -b option is used to specify the ID or sequence number of the backup, and is the same number shown by the management client in the Backup backup_id completed message displayed upon completion of a backup. (See Section 15.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup”.)

The path to the backup directory is required; this is supplied to ndb_restore using the --backup_path option, and must include the subdirectory corresponding to the ID backup of the backup to be restored. For example, if the data node's DataDir is /var/lib/mysql-cluster, then the backup directory is /var/lib/mysql-cluster/BACKUP, and the backup files for the backup with the ID 3 can be found in /var/lib/mysql-cluster/BACKUP/BACKUP-3. The path may be absolute or relative to the directory in which the ndb_restore executable is located, and may be optionally prefixed with backup_path=.

It is possible to restore a backup to a database with a different configuration than it was created from. For example, suppose that a backup with backup ID 12, created in a cluster with two database nodes having the node IDs 2 and 3, is to be restored to a cluster with four nodes. Then ndb_restore must be run twice — once for each database node in the cluster where the backup was taken. However, ndb_restore cannot always restore backups made from a cluster running one version of MySQL to a cluster running a different MySQL version. See Section 15.2.6.2, “MySQL Cluster 4.1 Upgrade and Downgrade Compatibility”, for more information.

For more rapid restoration, the data may be restored in parallel, provided that there is a sufficient number of cluster connections available. That is, when restoring to multiple nodes in parallel, you must have an [api] or [mysqld] section in the cluster config.ini file available for each concurrent ndb_restore process. However, the data files must always be applied before the logs.

Error reporting.  ndb_restore reports both temporary and permanent errors. In the case of temporary errors, it may able to recover from them. Beginning with MySQL 4.1.22, it reports Restore successful, but encountered temporary error, please look at configuration in such cases.