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ndb_mgmd − the NDB Cluster management server daemon


ndb_mgmd options


The management server is the process that reads the cluster configuration file and distributes this information to all nodes in the cluster that request it. It also maintains a log of cluster activities. Management clients can connect to the management server and check the cluster's status.

All options that can be used with ndb_mgmd are shown in the following table. Additional descriptions follow the table.

Table 23.26. Command−line options used with the program ndb_mgmd


Causes the management server to bind to a specific network interface (host name or IP address). This option has no default value.


Directory containing character sets.


Override defaults group suffix when reading cluster configuration sections in my.cnf; used in testing.


This option, whose default value is 1 (or TRUE, or ON), can be used to disable the management server's configuration cache, so that it reads its configuration from config.ini every time it starts (see Section 23.4.3, “NDB Cluster Configuration Files”). You can do this by starting the ndb_mgmd process with any one of the following options:





Using one of the options just listed is effective only if the management server has no stored configuration at the time it is started. If the management server finds any configuration cache files, then the −−config−cache option or the −−skip−config−cache option is ignored. Therefore, to disable configuration caching, the option should be used the first time that the management server is started. Otherwise—that is, if you wish to disable configuration caching for a management server that has already created a configuration cache—you must stop the management server, delete any existing configuration cache files manually, then restart the management server with −−skip−config−cache (or with −−config−cache set equal to 0, OFF, or FALSE).

Configuration cache files are normally created in a directory named mysql−cluster under the installation directory (unless this location has been overridden using the −−configdir option). Each time the management server updates its configuration data, it writes a new cache file. The files are named sequentially in order of creation using the following format:


node−id is the management server's node ID; seq−number is a sequence number, beginning with 1. For example, if the management server's node ID is 5, then the first three configuration cache files would, when they are created, be named ndb_5_config.bin.1, ndb_5_config.bin.2, and ndb_5_config.bin.3.

If your intent is to purge or reload the configuration cache without actually disabling caching, you should start ndb_mgmd with one of the options −−reload or −−initial instead of −−skip−config−cache.

To re−enable the configuration cache, simply restart the management server, but without the −−config−cache or −−skip−config−cache option that was used previously to disable the configuration cache.

ndb_mgmd does not check for the configuration directory (−−configdir) or attempts to create one when −−skip−config−cache is used. (Bug #13428853)

−−config−file=filename, −f filename

Instructs the management server as to which file it should use for its configuration file. By default, the management server looks for a file named config.ini in the same directory as the ndb_mgmd executable; otherwise the file name and location must be specified explicitly.

This option has no default value, and is ignored unless the management server is forced to read the configuration file, either because ndb_mgmd was started with the −−reload or −−initial option, or because the management server could not find any configuration cache.

The −−config−file option is also read if ndb_mgmd was started with −−config−cache=OFF. See Section 23.4.3, “NDB Cluster Configuration Files”, for more information.


Specifies the cluster management server's configuration cache directory. −−config−dir is an alias for this option.

In NDB 8.0.27 and later, this must be an absolute path. Otherwise, the management server refuses to start.


Number of times to retry connection before giving up.


Number of seconds to wait between attempts to contact management server.


Same as −−ndb−connectstring.


Write core file on error; used in debugging.

−−daemon, −d

Instructs ndb_mgmd to start as a daemon process. This is the default behavior.

This option has no effect when running ndb_mgmd on Windows platforms.


Read given file after global files are read.


Read default options from given file only.


Also read groups with concat(group, suffix).


Display help text and exit.


Configuration data is cached internally, rather than being read from the cluster global configuration file each time the management server is started (see Section 23.4.3, “NDB Cluster Configuration Files”). Using the −−initial option overrides this behavior, by forcing the management server to delete any existing cache files, and then to re−read the configuration data from the cluster configuration file and to build a new cache.

This differs in two ways from the −−reload option. First, −−reload forces the server to check the configuration file against the cache and reload its data only if the contents of the file are different from the cache. Second, −−reload does not delete any existing cache files.

If ndb_mgmd is invoked with −−initial but cannot find a global configuration file, the management server cannot start.

When a management server starts, it checks for another management server in the same NDB Cluster and tries to use the other management server's configuration data. This behavior has implications when performing a rolling restart of an NDB Cluster with multiple management nodes. See Section 23.6.5, “Performing a Rolling Restart of an NDB Cluster”, for more information.

When used together with the −−config−file option, the cache is cleared only if the configuration file is actually found.


Causes ndb_mgmd to be installed as a Windows service. Optionally, you can specify a name for the service; if not set, the service name defaults to ndb_mgmd. Although it is preferable to specify other ndb_mgmd program options in a my.ini or my.cnf configuration file, it is possible to use them together with −−install. However, in such cases, the −−install option must be specified first, before any other options are given, for the Windows service installation to succeed.

It is generally not advisable to use this option together with the −−initial option, since this causes the configuration cache to be wiped and rebuilt every time the service is stopped and started. Care should also be taken if you intend to use any other ndb_mgmd options that affect the starting of the management server, and you should make absolutely certain you fully understand and allow for any possible consequences of doing so.

The −−install option has no effect on non−Windows platforms.


Starts ndb_mgmd in interactive mode; that is, an ndb_mgm client session is started as soon as the management server is running. This option does not start any other NDB Cluster nodes.


Provides a name to be used for this node in the cluster log.


Read given path from login file.


Read configuration data from the my.cnf file.


Set connection string. Syntax: [nodeid=id;][host=]hostname[:port]. Overrides entries in NDB_CONNECTSTRING and my.cnf. Ignored if −−config−file is specified; beginning with NDB 8.0.27, a warning is issued when both options are used.


Same as −−ndb−connectstring.


Set node ID for this node, overriding any ID set by −−ndb−connectstring.


Enable optimizations for selection of nodes for transactions. Enabled by default; use −−skip−ndb−optimized−node−selection to disable.


Do not perform any checks of node IDs.


Instructs ndb_mgmd not to start as a daemon process.

The default behavior for ndb_mgmd on Windows is to run in the foreground, making this option unnecessary on Windows platforms.


Do not read default options from any option file other than login file.


When starting an NDB Cluster is configured with two management nodes, each management server normally checks to see whether the other ndb_mgmd is also operational and whether the other management server's configuration is identical to its own. However, it is sometimes desirable to start the cluster with only one management node (and perhaps to allow the other ndb_mgmd to be started later). This option causes the management node to bypass any checks for any other management nodes whose node IDs are passed to this option, permitting the cluster to start as though configured to use only the management node that was started.

For purposes of illustration, consider the following portion of a config.ini file (where we have omitted most of the configuration parameters that are not relevant to this example):

NodeId = 1
HostName =
NodeId = 2
HostName =
NodeId = 3
HostName =
NodeId = 4
HostName =
NodeId = 10
HostName =
NodeId = 11
HostName =
NodeId = 20
HostName =
NodeId = 21
HostName =

Assume that you wish to start this cluster using only the management server having node ID 10 and running on the host having the IP address (Suppose, for example, that the host computer on which you intend to the other management server is temporarily unavailable due to a hardware failure, and you are waiting for it to be repaired.) To start the cluster in this way, use a command line on the machine at to enter the following command:

$> ndb_mgmd −−ndb−nodeid=10 −−nowait−nodes=11

As shown in the preceding example, when using −−nowait−nodes, you must also use the −−ndb−nodeid option to specify the node ID of this ndb_mgmd process.

You can then start each of the cluster's data nodes in the usual way. If you wish to start and use the second management server in addition to the first management server at a later time without restarting the data nodes, you must start each data node with a connection string that references both management servers, like this:

$> ndbd −c,

The same is true with regard to the connection string used with any mysqld processes that you wish to start as NDB Cluster SQL nodes connected to this cluster. See Section, “NDB Cluster Connection Strings”, for more information.

When used with ndb_mgmd, this option affects the behavior of the management node with regard to other management nodes only. Do not confuse it with the −−nowait−nodes option used with ndbd or ndbmtd to permit a cluster to start with fewer than its full complement of data nodes; when used with data nodes, this option affects their behavior only with regard to other data nodes.

Multiple management node IDs may be passed to this option as a comma−separated list. Each node ID must be no less than 1 and no greater than 255. In practice, it is quite rare to use more than two management servers for the same NDB Cluster (or to have any need for doing so); in most cases you need to pass to this option only the single node ID for the one management server that you do not wish to use when starting the cluster.

When you later start the “missing” management server, its configuration must match that of the management server that is already in use by the cluster. Otherwise, it fails the configuration check performed by the existing management server, and does not start.


Print program argument list and exit.

−−print−full−config, −P

Shows extended information regarding the configuration of the cluster. With this option on the command line the ndb_mgmd process prints information about the cluster setup including an extensive list of the cluster configuration sections as well as parameters and their values. Normally used together with the −−config−file (−f) option.


NDB Cluster configuration data is stored internally rather than being read from the cluster global configuration file each time the management server is started (see Section 23.4.3, “NDB Cluster Configuration Files”). Using this option forces the management server to check its internal data store against the cluster configuration file and to reload the configuration if it finds that the configuration file does not match the cache. Existing configuration cache files are preserved, but not used.

This differs in two ways from the −−initial option. First, −−initial causes all cache files to be deleted. Second, −−initial forces the management server to re−read the global configuration file and construct a new cache.

If the management server cannot find a global configuration file, then the −−reload option is ignored.

When −−reload is used, the management server must be able to communicate with data nodes and any other management servers in the cluster before it attempts to read the global configuration file; otherwise, the management server fails to start. This can happen due to changes in the networking environment, such as new IP addresses for nodes or an altered firewall configuration. In such cases, you must use −−initial instead to force the exsiting cached configuration to be discarded and reloaded from the file. See Section 23.6.5, “Performing a Rolling Restart of an NDB Cluster”, for additional information.


Remove a management server process that has been installed as a Windows service, optionally specifying the name of the service to be removed. Applies only to Windows platforms.


Do not read cluster configuration file; ignore −−initial and −−reload options if specified.


Display help text and exit; same as −−help.

−−verbose, −v

Remove a management server process that has been installed as a Windows service, optionally specifying the name of the service to be removed. Applies only to Windows platforms.


Display version information and exit.

It is not strictly necessary to specify a connection string when starting the management server. However, if you are using more than one management server, a connection string should be provided and each node in the cluster should specify its node ID explicitly.

See Section, “NDB Cluster Connection Strings”, for information about using connection strings. ndb_mgmd(8), describes other options for ndb_mgmd.

The following files are created or used by ndb_mgmd in its starting directory, and are placed in the DataDir as specified in the config.ini configuration file. In the list that follows, node_id is the unique node identifier.

• config.ini is the configuration file for the cluster as a whole. This file is created by the user and read by the management server. Section 23.4, “Configuration of NDB Cluster”, discusses how to set up this file.

• ndb_node_id_cluster.log is the cluster events log file. Examples of such events include checkpoint startup and completion, node startup events, node failures, and levels of memory usage. A complete listing of cluster events with descriptions may be found in Section 23.6, “Management of NDB Cluster”.

By default, when the size of the cluster log reaches one million bytes, the file is renamed to ndb_node_id_cluster.log.seq_id, where seq_id is the sequence number of the cluster log file. (For example: If files with the sequence numbers 1, 2, and 3 already exist, the next log file is named using the number 4.) You can change the size and number of files, and other characteristics of the cluster log, using the LogDestination configuration parameter.

• ndb_node_id_out.log is the file used for stdout and stderr when running the management server as a daemon.

• ndb_node_id.pid is the process ID file used when running the management server as a daemon.


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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/.


Oracle Corporation (http://dev.mysql.com/).