Linux Certif

Toute la documentation sur la certification Linux LPI

ndb_restore

NAME

ndb_restore - restore a MySQL Cluster backup

SYNOPSIS

ndb_restore options

DESCRIPTION

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 7.3.2, "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.

Note

Before using ndb_restore, it is recommended that the cluster be running in single user mode, unless you are restoring multiple data nodes in parallel. See Section 7.6, "MySQL Cluster Single User Mode", for more information about single user mode.

Typical options for this utility are shown here:

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

The -c option is used to specify a connectstring which tells ndb_restore where to locate the cluster management server. (See Section 3.4.3, "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 3.4.7, "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. You should also remove manually any Disk Data files present in the data node's DataDir.)

It is possible to restore data without restoring table metadata. Prior to MySQL 5.1.17, ndb_restore did not perform any checks of table schemas; if a table was altered between the time the backup was taken and when ndb_restore was run, ndb_restore would still attempt to restore the data to the altered table.

Beginning with MySQL 5.1.17, the default behavior is for ndb_restore is to fail with an error if table data do not match the table schema; this can be overridden using the --skip-table-check or -s option. Prior to MySQL 5.1.21, if this option is used, then ndb_restore attempts to fit data into the existing table schema, but the result of restoring a backup to a table schema that does not match the original is unspecified.

Beginning with MySQL Cluster NDB 6.3.8, ndb_restore supports limited attribute promotion in much the same way that it is supported by MySQL replication; that is, data backed up from a column of a given type can generally be restored to a column using a "larger, similar" type. For example, data from a CHAR(20) column can be restored to a column declared as VARCHAR(20), VARCHAR(30), or CHAR(30); data from a MEDIUMINT column can be restored to a column of type INT or BIGINT. See Section 3.1.4.2, "Replication of Columns Having Different Data Types", for a table of type conversions currently supported by attribute promotion.

Attribute promotion by ndb_restore must be enabled explicitly, as follows:

1.

Prepare the table to which the backup is to be restored. ndb_restore cannot be used to re-create the table with a different definition from the original; this means that you must either create the table manually, or alter the columns which you wish to promote using ALTER TABLE after restoring the table metadata but before restoring the data.

2.

Invoke ndb_restore with the --promote-attributes option (short form -A) when restoring the table data. Attribute promotion does not occur if this option is not used; instead, the restore operation fails with an error.

In addition to --promote-attributes, a --preserve-trailing-spaces option is also available for use with ndb_restore beginning with MySQL 5.1.23-ndb-6.3.8. This option (short form -R) causes trailing spaces to be preserved when promoting a CHAR column to VARCHAR or a BINARY column to VARBINARY. Otherwise, any trailing spaces are dropped from column values when they are inserted into the new columns.

Note

Although you can promote CHAR columns to VARCHAR and BINARY columns to VARBINARY, you cannot promote VARCHAR columns to CHAR or VARBINARY columns to BINARY.

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 7.3.2, "Using The MySQL Cluster Management Client to Create a Backup".)

-e adds (or restores) epoch information to the cluster replication status table. This is useful for starting replication on a MySQL Cluster replication slave. When this option is used, the row in the mysql.ndb_apply_status having 0 in the id column is updated if it already exists; such a row is inserted if it does not already exist. (See Section 10.9, "MySQL Cluster Backups With Replication".)

The path to the backup directory is required, 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=.

Important

When restoring cluster backups, you must be sure to restore all data nodes from backups having the same backup ID. Using files from different backups will at best result in restoring the cluster to an inconsistent state, and may fail altogether.

Important

It is not possible to restore a backup made from a newer version of MySQL Cluster using an older version of ndb_restore. You can restore a backup made from a newer version of MySQL to an older cluster, but you must use a copy of ndb_restore from the newer MySQL Cluster version to do so.

For example, to restore a cluster backup taken from a cluster running MySQL 5.1.23 to a cluster running MySQL Cluster 5.1.20, you must use a copy of ndb_restore from the 5.1.23 distribution.

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 5.2, "MySQL Cluster 5.1 and MySQL Cluster NDB 6.x Upgrade and Downgrade Compatibility", for more information.

Note

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.

Formerly, when using ndb_restore to restore a backup made from a MySQL 5.0 cluster to a 5.1 cluster, VARCHAR columns were not resized and were recreated using the 5.0 fixed format. Beginning with MySQL 5.1.19, ndb_restore recreates such VARCHAR columns using MySQL Cluster 5.1's variable-width format. Also beginning with MySQL 5.1.19, this behavior can be overridden using the --no-upgrade option (short form: -u) when running ndb_restore.

Most of the options available for this program are shown in the following table:

Long Form	Short Form	Description	Default Value
--ndb-mgmd-host	None	Set the host and port in                     host[:port]                     format for the management server to connect to; this                     is the same as --connect,                     --connectstring, or                     --ndb-connectstring, but without a                     way to specify the nodeid	None
--ndb-nodegroup-map	-z	Specifies a nodegroup map --- Syntax: list of                     (source_nodegroup,                     destination_nodegroup)	None
--ndb-nodeid	None	Specify a node ID for the ndb_restore process	0
--ndb-optimized-node-selection	None	Optimize selection of nodes for transactions	TRUE
--ndb-shm	None	Use shared memory connections when available	FALSE
--no-binlog	None	Do not write anything to mysqld binary logs (added in                     MySQL Cluster NDB 6.2.16 and 6.3.16)	FALSE (in other words, write to binary logs unless                     this option is used)
--no-restore-disk-objects	-d	Do not restore Disk Data objects such as tablespaces and log file groups	FALSE (in other words, restore Disk Data objects                     unless this option is used)
--no-upgrade	-u	Do not re-create VARSIZE columns from a MySQL 5.0                     Cluster backup as variable-width columns (added in                     MySQL 5.1.19)	FALSE (in other words, re-create                     VARSIZE columns from a MySQL 5.0                     Cluster backup as variable-width columns unless this                     option is used)
--nodeid	-n	Use backup files from node with the specified ID	0
--parallelism	-p	Set from 1 to 1024 parallel transactions to be used during the                     restoration process	128
--backup-id	-b	Backup sequence ID	0
--print	None	Print metadata, data, and log to stdout	FALSE
--print_data	None	Print data to stdout	FALSE
--print_log	None	Print log to stdout	FALSE
--print_meta	None	Print metadata to stdout	FALSE
--restore_data	-r	Restore data and logs	FALSE
--restore_epoch	-e	Restore epoch data into the status table; the row in the                     cluster.apply_status having the                     id 0 is inserted or updated as                     appropriate --- this is convenient when starting                     up replication on a MySQL Cluster replication slave	FALSE
--restore_meta	-m	Restore table metadata	FALSE
--skip-table-check	-s	Do not check table schemas (Added in MySQL 5.1.17)	FALSE
--version	-V	Output version information and exit	[N/A]
--backup_path	None	Path to backup files	./
--character-sets-dir	None	Specify the directory where character set information can be found	None
--connect, --connectstring, or                     --ndb-connectstring	-c or -C	Set the connectstring in                     [nodeid=node_id;][host=]host[:port]                     format	localhost:1186
--core-file	None	Write a core file in the event of an error	TRUE
--debug	-#	Output debug log	d:t:O,/tmp/ndb_restore.trace
--dont_ignore_systab_0	-f	Do not ignore system table during restore ---                     EXPERIMENTAL; not for production                     use	FALSE
--help or --usage	-?	Display help message with available options and current values, then                     exit	[N/A]

Beginning with MySQL 5.1.18, several additional options are available for use with the --print_data option in generating data dumps, either to stdout, or to a file. These are similar to some of the options used with mysqldump, and are shown in the following table:

Note

If a table has no explicit primary key, then the output generated when using the --print includes the table's hidden primary key.

Beginning with MySQL 5.1.18, it is possible to restore selected databases, or to restore selected tables from a given database using the syntax shown here:

 ndb_restore other_options db_name_1 [db_name_2[, db_name_3][, ...] | tbl_name_1[, tbl_name_2][, ...]]
 

In other words, you can specify either of the following to be restored:

•

All tables from one or more databases

•

One or more tables from a single database

Note

ndb_restore reports both temporary and permanent errors. In the case of temporary errors, it may able to recover from them. Beginning with MySQL 5.1.12, it reports Restore successful, but encountered temporary error, please look at configuration in such cases.

COPYRIGHT

Copyright 2007-2008 MySQL AB, 2009 Sun Microsystems, Inc.

This documentation is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.

SEE ALSO

For more information, please refer to the MySQL Reference Manual, which may already be installed locally and which is also available online at http://dev.mysql.com/doc/.

AUTHOR

MySQL AB (http://www.mysql.com/).