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MySQL 5.6 Reference Manual  /  ...  /  Server Command Options

5.1.6 Server Command Options

When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.2, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 4.2.2.2, “Using Option Files”. That section also describes option file format and syntax.

mysqld reads options from the [mysqld] and [server] groups. mysqld_safe reads options from the [mysqld], [server], [mysqld_safe], and [safe_mysqld] groups. mysql.server reads options from the [mysqld] and [mysql.server] groups.

An embedded MySQL server usually reads options from the [server], [embedded], and [xxxxx_SERVER] groups, where xxxxx is the name of the application into which the server is embedded.

mysqld accepts many command options. For a brief summary, execute this command: 

mysqld --help

To see the full list, use this command: 

mysqld --verbose --help

Some of the items in the list are actually system variables that can be set at server startup. These can be displayed at runtime using the SHOW VARIABLES statement. Some items displayed by the preceding mysqld command do not appear in SHOW VARIABLES output; this is because they are options only and not system variables.

The following list shows some of the most common server options. Additional options are described in other sections:

Some options control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to an option that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.

Some options take file name values. Unless otherwise specified, the default file location is the data directory if the value is a relative path name. To specify the location explicitly, use an absolute path name. Suppose that the data directory is /var/mysql/data. If a file-valued option is given as a relative path name, it will be located under /var/mysql/data. If the value is an absolute path name, its location is as given by the path name.

You can also set the values of server system variables at server startup by using variable names as options. To assign a value to a server system variable, use an option of the form --var_name=value. For example, --key_buffer_size=32M sets the key_buffer_size variable to a value of 32MB.

When you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.

To restrict the maximum value to which a system variable can be set at runtime with the SET statement, specify this maximum by using an option of the form --maximum-var_name=value at server startup.

You can change the values of most system variables at runtime with the SET statement. See Section 13.7.4.1, “SET Syntax for Variable Assignment”.

Section 5.1.7, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. For information on changing system variables, see Section 5.1.1, “Configuring the Server”.

  • --help, -?

    Property Value
    Command-Line Format --help

    Display a short help message and exit. Use both the --verbose and --help options to see the full message.

  • --allow-suspicious-udfs

    Property Value
    Command-Line Format --allow-suspicious-udfs[={OFF|ON}]
    Type Boolean
    Default Value OFF

    This option controls whether user-defined functions that have only an xxx symbol for the main function can be loaded. By default, the option is off and only UDFs that have at least one auxiliary symbol can be loaded; this prevents attempts at loading functions from shared object files other than those containing legitimate UDFs. See UDF Security Precautions.

  • --ansi

    Property Value
    Command-Line Format --ansi

    Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise control over the server SQL mode, use the --sql-mode option instead. See Section 1.7, “MySQL Standards Compliance”, and Section 5.1.10, “Server SQL Modes”.

  • --basedir=dir_name, -b dir_name

    Property Value
    Command-Line Format --basedir=dir_name
    System Variable basedir
    Scope Global
    Dynamic No
    Type Directory name
    Default Value configuration-dependent default

    The path to the MySQL installation directory. This option sets the basedir system variable.

  • --bind-address=addr

    Property Value
    Command-Line Format --bind-address=addr
    Introduced 5.6.1
    System Variable bind_address
    Scope Global
    Dynamic No
    Type String
    Default Value (>= 5.6.6) *
    Default Value (<= 5.6.5) 0.0.0.0

    This option was removed in MySQL 5.6.1. Use the bind_address system variable instead.

  • --bootstrap

    Property Value
    Command-Line Format --bootstrap

    This option is used by the mysql_install_db program to create the MySQL privilege tables without having to start a full MySQL server.

    Replication and global transaction identifiers are automatically disabled whenever this option is used (Bug #13992602). See Section 17.1.3, “Replication with Global Transaction Identifiers”.

    When the server operates in bootstap mode, some functionality is unavailable that limits the statements permitted in any file named by the init_file system variable. For more information, see the description of that variable.

  • --character-set-client-handshake

    Property Value
    Command-Line Format --character-set-client-handshake[={OFF|ON}]
    Type Boolean
    Default Value ON

    Do not ignore character set information sent by the client. To ignore client information and use the default server character set, use --skip-character-set-client-handshake; this makes MySQL behave like MySQL 4.0.

  • --chroot=dir_name, -r dir_name

    Property Value
    Command-Line Format --chroot=dir_name
    Type Directory name

    Put the mysqld server in a closed environment during startup by using the chroot() system call. This is a recommended security measure.

    Note

    Use of this option somewhat limits LOAD DATA and SELECT ... INTO OUTFILE.

  • --console

    Property Value
    Command-Line Format --console
    Platform Specific Windows

    (Windows only.) Write error log messages to stderr and stdout (the console). mysqld does not close the console window if this option is used.

    --log-error takes precedence over --console if both are given.

  • --core-file

    Property Value
    Command-Line Format --core-file[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Write a core file if mysqld dies. The name and location of the core file is system dependent. On Linux, a core file named core.pid is written to the current working directory of the process, which for mysqld is the data directory. pid represents the process ID of the server process. On macOS, a core file named core.pid is written to the /cores directory. On Solaris, use the coreadm command to specify where to write the core file and how to name it.

    For some systems, to get a core file you must also specify the --core-file-size option to mysqld_safe. See Section 4.3.2, “mysqld_safe — MySQL Server Startup Script”. On some systems, such as Solaris, you do not get a core file if you are also using the --user option. There might be additional restrictions or limitations. For example, it might be necessary to execute ulimit -c unlimited before starting the server. Consult your system documentation.

  • --datadir=dir_name, -h dir_name

    Property Value
    Command-Line Format --datadir=dir_name
    System Variable datadir
    Scope Global
    Dynamic No
    Type Directory name

    The path to the MySQL server data directory. This option sets the datadir system variable. See the description of that variable.

  • --debug[=debug_options], -# [debug_options]

    Property Value
    Command-Line Format --debug[=debug_options]
    System Variable debug
    Scope Global, Session
    Dynamic Yes
    Type String
    Default Value (Windows) d:t:i:O,\mysqld.trace
    Default Value (Unix) d:t:i:o,/tmp/mysqld.trace

    If MySQL is configured with the -DWITH_DEBUG=1 CMake option, you can use this option to get a trace file of what mysqld is doing. A typical debug_options string is d:t:o,file_name. The default is d:t:i:o,/tmp/mysqld.trace on Unix and d:t:i:O,\mysqld.trace on Windows.

    Using -DWITH_DEBUG=1 to configure MySQL with debugging support enables you to use the --debug="d,parser_debug" option when you start the server. This causes the Bison parser that is used to process SQL statements to dump a parser trace to the server's standard error output. Typically, this output is written to the error log.

    This option may be given multiple times. Values that begin with + or - are added to or subtracted from the previous value. For example, --debug=T --debug=+P sets the value to P:T.

    For more information, see Section 24.5.3, “The DBUG Package”.

  • --debug-sync-timeout[=N]

    Property Value
    Command-Line Format --debug-sync-timeout[=#]
    Type Integer

    Controls whether the Debug Sync facility for testing and debugging is enabled. Use of Debug Sync requires that MySQL be configured with the -DENABLE_DEBUG_SYNC=1 CMake option (see Section 2.9.7, “MySQL Source-Configuration Options”). If Debug Sync is not compiled in, this option is not available. The option value is a timeout in seconds. The default value is 0, which disables Debug Sync. To enable it, specify a value greater than 0; this value also becomes the default timeout for individual synchronization points. If the option is given without a value, the timeout is set to 300 seconds.

    For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.

  • --default-authentication-plugin=plugin_name

    Property Value
    Command-Line Format --default-authentication-plugin=plugin_name
    Introduced 5.6.6
    Type Enumeration
    Default Value mysql_native_password
    Valid Values

    mysql_native_password

    sha256_password

    This option sets the default authentication plugin. These values are permitted:

    Note

    Prior to MySQL 5.6.17, if you use this option to change the default authentication plugin to a value other than mysql_native_password, clients older than MySQL 5.5.7 cannot connect because they do not understand the resulting change to the authentication protocol.

    In MySQL 5.6, there is no server system variable that corresponds to the --default-authentication-plugin option; to read the value set for this option, you must check the running MySQL Server process to see what options, if any, were employed when invoking mysqld (on Linux systems, you can do this with ps ax | grep mysqld or similar), and possibly the server options file as well. This is a known issue which is resolved in MySQL 5.7. (Bug #68858, Bug #16595944)

    The --default-authentication-plugin value affects these aspects of server operation:

    • It determines which authentication plugin the server assigns to new accounts created by CREATE USER and GRANT statements that do not explicitly specify an authentication plugin.

    • The old_passwords system variable affects password hashing for accounts that use the mysql_native_password or sha256_password authentication plugin. If the default authentication plugin is one of those plugins, the server sets old_passwords at startup to the value required by the plugin password hashing method.

    • For an account created with either of the following statements, the server associates the account with the default authentication plugin and assigns the account the given password, hashed as required by that plugin: 

      CREATE USER ... IDENTIFIED BY 'cleartext password';
GRANT ...  IDENTIFIED BY 'cleartext password';

    • For an account created with either of the following statements, the server associates the account with the default authentication plugin and assigns the account the given password hash, if the password hash has the format required by the plugin: 

      CREATE USER ... IDENTIFIED BY PASSWORD 'encrypted password';
GRANT ...  IDENTIFIED BY PASSWORD 'encrypted password';

      If the password hash is not in the format required by the default authentication plugin, the statement fails.

  • --default-time-zone=timezone

    Property Value
    Command-Line Format --default-time-zone=name
    Type String

    Set the default server time zone. This option sets the global time_zone system variable. If this option is not given, the default time zone is the same as the system time zone (given by the value of the system_time_zone system variable.

  • --defaults-extra-file=file_name

    Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. file_name is interpreted relative to the current directory if given as a relative path name rather than a full path name. This must be the first option on the command line if it is used.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --defaults-file=file_name

    Read only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. file_name is interpreted relative to the current directory if given as a relative path name rather than a full path name.

    Note

    This must be the first option on the command line if it is used, except that if the server is started with the --defaults-file and --install (or --install-manual) options, --install (or --install-manual) must be first.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --defaults-group-suffix=str

    Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqld normally reads the [mysqld] group. If the --defaults-group-suffix=_other option is given, mysqld also reads the [mysqld_other] group.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --des-key-file=file_name

    Property Value
    Command-Line Format --des-key-file=file_name

    Read the default DES keys from this file. These keys are used by the DES_ENCRYPT() and DES_DECRYPT() functions.

  • --exit-info[=flags], -T [flags]

    Property Value
    Command-Line Format --exit-info[=flags]
    Type Integer

    This is a bitmask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!

  • --external-locking

    Property Value
    Command-Line Format --external-locking[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Enable external locking (system locking), which is disabled by default. If you use this option on a system on which lockd does not fully work (such as Linux), it is easy for mysqld to deadlock.

    To disable external locking explicitly, use --skip-external-locking.

    External locking affects only MyISAM table access. For more information, including conditions under which it can and cannot be used, see Section 8.11.5, “External Locking”.

  • --flush

    Property Value
    Command-Line Format --flush[={OFF|ON}]
    System Variable flush
    Scope Global
    Dynamic Yes
    Type Boolean
    Default Value OFF

    Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.4.3.3, “What to Do If MySQL Keeps Crashing”.

    Note

    If --flush is specified, the value of flush_time does not matter and changes to flush_time have no effect on flush behavior.

  • --gdb

    Property Value
    Command-Line Format --gdb[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Install an interrupt handler for SIGINT (needed to stop mysqld with ^C to set breakpoints) and disable stack tracing and core file handling. See Section 24.5.1.4, “Debugging mysqld under gdb”.

  • --ignore-db-dir=dir_name

    Property Value
    Command-Line Format --ignore-db-dir=dir_name
    Introduced 5.6.3
    Type Directory name

    This option tells the server to ignore the given directory name for purposes of the SHOW DATABASES statement or INFORMATION_SCHEMA tables. For example, if a MySQL configuration locates the data directory at the root of a file system on Unix, the system might create a lost+found directory there that the server should ignore. Starting the server with --ignore-db-dir=lost+found causes that name not to be listed as a database.

    To specify more than one name, use this option multiple times, once for each name. Specifying the option with an empty value (that is, as --ignore-db-dir=) resets the directory list to the empty list.

    Instances of this option given at server startup are used to set the ignore_db_dirs system variable.

  • --innodb-xxx

    Set an option for the InnoDB storage engine. The InnoDB options are listed in Section 14.14, “InnoDB Startup Options and System Variables”.

  • --install [service_name]

    Property Value
    Command-Line Format --install [service_name]
    Platform Specific Windows

    (Windows only) Install the server as a Windows service that starts automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.4.7, “Starting MySQL as a Windows Service”.

    Note

    If the server is started with the --defaults-file and --install options, --install must be first.

  • --install-manual [service_name]

    Property Value
    Command-Line Format --install-manual [service_name]
    Platform Specific Windows

    (Windows only) Install the server as a Windows service that must be started manually. It does not start automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.4.7, “Starting MySQL as a Windows Service”.

    Note

    If the server is started with the --defaults-file and --install-manual options, --install-manual must be first.

  • --language=lang_name, -L lang_name

    Property Value
    Command-Line Format --language=name
    Deprecated 5.6.1; use lc-messages-dir instead
    System Variable language
    Scope Global
    Dynamic No
    Type Directory name
    Default Value /usr/local/mysql/share/mysql/english/

    The language to use for error messages. lang_name can be given as the language name or as the full path name to the directory where the language files are installed. See Section 10.12, “Setting the Error Message Language”.

    --lc-messages-dir and --lc-messages should be used rather than --language, which is deprecated and handled as an alias for --lc-messages-dir. The --language option will be removed in a future MySQL release.

  • --large-pages

    Property Value
    Command-Line Format --large-pages[={OFF|ON}]
    System Variable large_pages
    Scope Global
    Dynamic No
    Platform Specific Linux
    Type Boolean
    Default Value OFF

    Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.

    MySQL supports the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.12.4.2, “Enabling Large Page Support”. For Solaris support of large pages, see the description of the --super-large-pages option.

    --large-pages is disabled by default.

  • --lc-messages=locale_name

    Property Value
    Command-Line Format --lc-messages=name
    System Variable lc_messages
    Scope Global, Session
    Dynamic Yes
    Type String
    Default Value en_US

    The locale to use for error messages. The default is en_US. The server converts the argument to a language name and combines it with the value of --lc-messages-dir to produce the location for the error message file. See Section 10.12, “Setting the Error Message Language”.

  • --lc-messages-dir=dir_name

    Property Value
    Command-Line Format --lc-messages-dir=dir_name
    System Variable lc_messages_dir
    Scope Global
    Dynamic No
    Type Directory name

    The directory where error messages are located. The server uses the value together with the value of --lc-messages to produce the location for the error message file. See Section 10.12, “Setting the Error Message Language”.

  • --local-service

    Property Value
    Command-Line Format --local-service

    (Windows only) A --local-service option following the service name causes the server to run using the LocalService Windows account that has limited system privileges. If both --defaults-file and --local-service are given following the service name, they can be in any order. See Section 2.3.4.7, “Starting MySQL as a Windows Service”.

  • --log[=file_name], -l [file_name]

    Property Value
    Command-Line Format --log[=file_name]
    Deprecated Yes (removed in 5.6.1); use general_log instead
    System Variable log
    Scope Global
    Dynamic Yes
    Type File name

    The --log option was removed in MySQL 5.6.1 (along with the log system variable). Instead, use the general_log system variable to enable the general query log and the general_log_file system variable to set the general query log file name.

  • --log-error[=file_name]

    Property Value
    Command-Line Format --log-error[=file_name]
    System Variable log_error
    Scope Global
    Dynamic No
    Type File name

    Write the error log and startup messages to this file. See Section 5.4.2, “The Error Log”.

    If the option names no file, the error log file name on Unix and Unix-like systems is host_name.err in the data directory. The file name on Windows is the same, unless the --pid-file option is specified. In that case, the file name is the PID file base name with a suffix of .err in the data directory.

    If the option names a file, the error log file has that name (with an .err suffix added if the name has no suffix), located under the data directory unless an absolute path name is given to specify a different location.

    On Windows, --log-error takes precedence over --console if both are given.

  • --log-isam[=file_name]

    Property Value
    Command-Line Format --log-isam[=file_name]
    Type File name

    Log all MyISAM changes to this file (used only when debugging MyISAM).

  • --log-raw

    Property Value
    Command-Line Format --log-raw[={OFF|ON}]
    Introduced 5.6.3
    Type Boolean
    Default Value OFF

    Passwords in certain statements written to the general query log, slow query log, and binary log are rewritten by the server not to occur literally in plain text. Password rewriting can be suppressed for the general query log by starting the server with the --log-raw option. This option may be useful for diagnostic purposes, to see the exact text of statements as received by the server, but for security reasons is not recommended for production use.

  • --log-short-format

    Property Value
    Command-Line Format --log-short-format[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Log less information to the slow query log, if it has been activated.

  • --log-slow-admin-statements

    Property Value
    Command-Line Format --log-slow-admin-statements[={OFF|ON}] (<= 5.6.10)
    Removed 5.6.11
    Type Boolean
    Default Value OFF

    Include slow administrative statements in the statements written to the slow query log. Administrative statements include ALTER TABLE, ANALYZE TABLE, CHECK TABLE, CREATE INDEX, DROP INDEX, OPTIMIZE TABLE, and REPAIR TABLE.

    This command-line option was removed in MySQL 5.6.11 and replaced by the log_slow_admin_statements system variable. The system variable can be set on the command line or in option files the same way as the option, so there is no need for any changes at server startup, but the system variable also makes it possible to examine or set the value at runtime.

  • --log-tc=file_name

    Property Value
    Command-Line Format --log-tc=file_name
    Type File name
    Default Value tc.log

    The name of the memory-mapped transaction coordinator log file (for XA transactions that affect multiple storage engines when the binary log is disabled). The default name is tc.log. The file is created under the data directory if not given as a full path name. This option is unused.

  • --log-tc-size=size

    Property Value
    Command-Line Format --log-tc-size=#
    Type Integer
    Default Value 24576
    Maximum Value (64-bit platforms) 18446744073709551615
    Maximum Value (32-bit platforms) 4294967295

    The size in bytes of the memory-mapped transaction coordinator log. The default size is 24KB.

  • --log-warnings[=level], -W [level]

    Property Value
    Command-Line Format --log-warnings[=#]
    System Variable log_warnings
    Scope (>= 5.6.4) Global
    Scope (<= 5.6.3) Global, Session
    Dynamic Yes
    Type Integer
    Default Value 1
    Minimum Value 0
    Maximum Value (64-bit platforms) 18446744073709551615
    Maximum Value (32-bit platforms) 4294967295

    Print out warnings such as Aborted connection... to the error log. This option is enabled (1) by default. To disable it, use --log-warnings=0. Specifying the option without a level value increments the current value by 1. Enabling this option by setting it greater than 0 is recommended, for example, if you use replication (you get more information about what is happening, such as messages about network failures and reconnections). If the value is greater than 1, aborted connections are written to the error log, and access-denied errors for new connection attempts are written. See Section B.4.2.11, “Communication Errors and Aborted Connections”.

    If a slave server was started with --log-warnings enabled, the slave prints messages to the error log to provide information about its status, such as the binary log and relay log coordinates where it starts its job, when it is switching to another relay log, when it reconnects after a disconnect, and so forth. The server logs messages about statements that are unsafe for statement-based logging if --log-warnings is greater than 0.

  • --memlock

    Property Value
    Command-Line Format --memlock[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.

    --memlock works on systems that support the mlockall() system call; this includes Solaris, most Linux distributions that use a 2.4 or higher kernel, and perhaps other Unix systems. On Linux systems, you can tell whether or not mlockall() (and thus this option) is supported by checking to see whether or not it is defined in the system mman.h file, like this: 

    shell> grep mlockall /usr/include/sys/mman.h

    If mlockall() is supported, you should see in the output of the previous command something like the following: 

    extern int mlockall (int __flags) __THROW;
    Important

    Use of this option may require you to run the server as root, which, for reasons of security, is normally not a good idea. See Section 6.1.5, “How to Run MySQL as a Normal User”.

    On Linux and perhaps other systems, you can avoid the need to run the server as root by changing the limits.conf file. See the notes regarding the memlock limit in Section 8.12.4.2, “Enabling Large Page Support”.

    You must not try to use this option on a system that does not support the mlockall() system call; if you do so, mysqld will very likely crash as soon as you try to start it.

  • --myisam-block-size=N

    Property Value
    Command-Line Format --myisam-block-size=#
    Type Integer
    Default Value 1024
    Minimum Value 1024
    Maximum Value 16384

    The block size to be used for MyISAM index pages.

  • --no-defaults

    Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read. This must be the first option on the command line if it is used.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --old-style-user-limits

    Property Value
    Command-Line Format --old-style-user-limits[={OFF|ON}]
    Type Boolean
    Default Value OFF

    Enable old-style user limits. (Before MySQL 5.0.3, account resource limits were counted separately for each host from which a user connected rather than per account row in the user table.) See Section 6.2.13, “Setting Account Resource Limits”.

  • --one-thread

    Property Value
    Command-Line Format --one-thread
    Removed 5.6.1

    This option was removed in MySQL 5.6.1. Use --thread_handling=no-threads instead.

  • --partition[=value]

    Property Value
    Command-Line Format --partition[={OFF|ON}]
    Disabled by skip-partition
    Type Boolean
    Default Value ON

    Enables or disables user-defined partitioning support in the MySQL Server.

  • --performance-schema-xxx

    Configure a Performance Schema option. For details, see Section 22.14, “Performance Schema Command Options”.

  • --plugin-load=plugin_list

    Property Value
    Command-Line Format --plugin-load=plugin_list
    System Variable plugin_load
    Scope Global
    Dynamic No
    Type String

    This option tells the server to load the named plugins at startup. If multiple --plugin-load options are given, only the last one is used. Additional plugins to load may be specified using --plugin-load-add options.

    The option value is a semicolon-separated list of name=plugin_library and plugin_library values. Each name is the name of a plugin to load, and plugin_library is the name of the library file that contains the plugin code. If a plugin library is named without any preceding plugin name, the server loads all plugins in the library. The server looks for plugin library files in the directory named by the plugin_dir system variable.

    For example, if plugins named myplug1 and myplug2 have library files myplug1.so and myplug2.so, use this option to perform an early plugin load: 

    shell> mysqld --plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"

    Quotes are used around the argument value here because otherwise semicolon (;) is interpreted as a special character by some command interpreters. (Unix shells treat it as a command terminator, for example.)

    Each named plugin is loaded for a single invocation of mysqld only. After a restart, the plugin is not loaded unless --plugin-load is used again. This is in contrast to INSTALL PLUGIN, which adds an entry to the mysql.plugins table to cause the plugin to be loaded for every normal server startup.

    Under normal startup, the server determines which plugins to load by reading the mysql.plugins system table. If the server is started with the --skip-grant-tables option, it does not consult the mysql.plugins table and does not load plugins listed there. --plugin-load enables plugins to be loaded even when --skip-grant-tables is given. --plugin-load also enables plugins to be loaded at startup that cannot be loaded at runtime.

    For additional information about plugin loading, see Section 5.5.1, “Installing and Uninstalling Plugins”.

  • --plugin-load-add=plugin_list

    Property Value
    Command-Line Format --plugin-load-add=plugin_list
    Introduced 5.6.3
    System Variable plugin_load_add
    Scope Global
    Dynamic No
    Type String

    This option complements the --plugin-load option. --plugin-load-add adds a plugin or plugins to the set of plugins to be loaded at startup. The argument format is the same as for --plugin-load. --plugin-load-add can be used to avoid specifying a large set of plugins as a single long unwieldy --plugin-load argument.

    --plugin-load-add can be given in the absence of --plugin-load, but any instance of --plugin-load-add that appears before --plugin-load. has no effect because --plugin-load resets the set of plugins to load. In other words, these options: 

    --plugin-load=x --plugin-load-add=y

    are equivalent to this option: 

    --plugin-load="x;y"

    But these options: 

    --plugin-load-add=y --plugin-load=x

    are equivalent to this option: 

    --plugin-load=x

    For additional information about plugin loading, see Section 5.5.1, “Installing and Uninstalling Plugins”.

  • --plugin-xxx

    Specifies an option that pertains to a server plugin. For example, many storage engines can be built as plugins, and for such engines, options for them can be specified with a --plugin prefix. Thus, the --innodb-file-per-table option for InnoDB can be specified as --plugin-innodb-file-per-table.

    For boolean options that can be enabled or disabled, the --skip prefix and other alternative formats are supported as well (see Section 4.2.2.4, “Program Option Modifiers”). For example, --skip-plugin-innodb-file-per-table disables innodb-file-per-table.

    The rationale for the --plugin prefix is that it enables plugin options to be specified unambiguously if there is a name conflict with a built-in server option. For example, were a plugin writer to name a plugin “sql” and implement a “mode” option, the option name might be --sql-mode, which would conflict with the built-in option of the same name. In such cases, references to the conflicting name are resolved in favor of the built-in option. To avoid the ambiguity, users can specify the plugin option as --plugin-sql-mode. Use of the --plugin prefix for plugin options is recommended to avoid any question of ambiguity.

  • --port=port_num, -P port_num

    Property Value
    Command-Line Format --port=port_num
    System Variable port
    Scope Global
    Dynamic No
    Type Integer
    Default Value 3306
    Minimum Value 0
    Maximum Value 65535

    The port number to use when listening for TCP/IP connections. On Unix and Unix-like systems, the port number must be 1024 or higher unless the server is started by the root operating system user. Setting this option to 0 causes the default value to be used.

  • --port-open-timeout=num

    Property Value
    Command-Line Format --port-open-timeout=#
    Type Integer
    Default Value 0

    On some systems, when the server is stopped, the TCP/IP port might not become available immediately. If the server is restarted quickly afterward, its attempt to reopen the port can fail. This option indicates how many seconds the server should wait for the TCP/IP port to become free if it cannot be opened. The default is not to wait.

  • --print-defaults

    Print the program name and all options that it gets from option files. This must be the first option on the command line if it is used, except that it may be used immediately after --defaults-file or --defaults-extra-file.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --remove [service_name]

    Property Value
    Command-Line Format --remove [service_name]
    Platform Specific Windows

    (Windows only) Remove a MySQL Windows service. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.4.7, “Starting MySQL as a Windows Service”.

  • --safe-mode

    Property Value
    Command-Line Format --safe-mode
    Deprecated Yes (removed in 5.6.6)

    Skip some optimization stages. This option was removed in MySQL 5.6.6.

  • --safe-user-create

    Property Value
    Command-Line Format --safe-user-create[={OFF|ON}]
    Type Boolean
    Default Value OFF

    If this option is enabled, a user cannot create new MySQL users by using the GRANT statement unless the user has the INSERT privilege for the mysql.user system table or any column in the table. If you want a user to have the ability to create new users that have those privileges that the user has the right to grant, you should grant the user the following privilege: 

    GRANT INSERT(user) ON mysql.user TO 'user_name'@'host_name';

    This ensures that the user cannot change any privilege columns directly, but has to use the GRANT statement to give privileges to other users.

  • --skip-grant-tables

    Property Value
    Command-Line Format --skip-grant-tables[={OFF|ON}]
    Type Boolean
    Default Value OFF

    This option affects the server startup sequence:

    • --skip-grant-tables causes the server not to read the grant tables in the mysql system database, and thus to start without using the privilege system at all. This gives anyone with access to the server unrestricted access to all databases.

      To cause a server started with --skip-grant-tables to load the grant tables at runtime, perform a privilege-flushing operation, which can be done in these ways:

      Privilege flushing might also occur implicitly as a result of other actions performed after startup, thus causing the server to start using the grant tables. For example, mysql_upgrade flushes the privileges during the upgrade procedure.

    • In addition to causing the startup sequence not to load the grant tables, --skip-grant-tables causes the server not to load certain other objects stored in the mysql system database: plugins that were installed with the INSTALL PLUGIN statement, scheduled events, and user-defined functions (UDFs). To cause plugins to be loaded anyway, use the --plugin-load or --plugin-load-add option.

  • --skip-host-cache

    Property Value
    Command-Line Format --skip-host-cache

    Disable use of the internal host cache for faster name-to-IP resolution. With the cache disabled, the server performs a DNS lookup every time a client connects.

    Use of --skip-host-cache is similar to setting the host_cache_size system variable to 0, but host_cache_size is more flexible because it can also be used to resize, enable, or disable the host cache at runtime, not just at server startup.

    If you start the server with --skip-host-cache, that does not prevent changes to the value of host_cache_size, but such changes have no effect and the cache is not re-enabled even if host_cache_size is set larger than 0.

    For more information about how the host cache works, see Section 8.12.5.2, “DNS Lookup Optimization and the Host Cache”.

  • --skip-innodb

    Disable the InnoDB storage engine. In this case, because the default storage engine is InnoDB, the server will not start unless you also use --default-storage-engine and --default-tmp-storage-engine to set the default to some other engine for both permanent and TEMPORARY tables.

    As of MySQL 5.6.21, the --skip-innodb option is deprecated. Its use results in a warning. This option will be removed in a future MySQL release.

  • --skip-new

    Property Value
    Command-Line Format --skip-new

    This option disables (what used to be considered) new, possibly unsafe behaviors. It results in these settings: delay_key_write=OFF, concurrent_insert=NEVER, automatic_sp_privileges=OFF. It also causes OPTIMIZE TABLE to be mapped to ALTER TABLE for storage engines for which OPTIMIZE TABLE is not supported.

  • --skip-partition

    Property Value
    Command-Line Format

    --skip-partition

    --disable-partition

    Disables user-defined partitioning. Partitioned tables can be seen using SHOW TABLES or by querying the INFORMATION_SCHEMA.TABLES table, but cannot be created or modified, nor can data in such tables be accessed. All partition-specific columns in the INFORMATION_SCHEMA.PARTITIONS table display NULL.

    Since DROP TABLE removes table definition (.frm) files, this statement works on partitioned tables even when partitioning is disabled using the option. The statement, however, does not remove .par files associated with partitioned tables in such cases. For this reason, you should avoid dropping partitioned tables with partitioning disabled, or take action to remove the orphaned .par files manually.

  • --skip-show-database

    Property Value
    Command-Line Format --skip-show-database
    System Variable skip_show_database
    Scope Global
    Dynamic No

    This option sets the skip_show_database system variable that controls who is permitted to use the SHOW DATABASES statement. See Section 5.1.7, “Server System Variables”.

  • --skip-stack-trace

    Property Value
    Command-Line Format --skip-stack-trace

    Do not write stack traces. This option is useful when you are running mysqld under a debugger. On some systems, you also must use this option to get a core file. See Section 24.5, “Debugging and Porting MySQL”.

  • --skip-thread-priority

    Property Value
    Command-Line Format --skip-thread-priority
    Deprecated Yes (removed in 5.6.1)

    Disable using thread priorities for faster response time. This option was unused and was removed in MySQL 5.6.1.

  • --slow-start-timeout=timeout

    Property Value
    Command-Line Format --slow-start-timeout=#
    Introduced 5.6.5
    Type Integer
    Default Value 15000

    This option controls the Windows service control manager's service start timeout. The value is the maximum number of milliseconds that the service control manager waits before trying to kill the windows service during startup. The default value is 15000 (15 seconds). If the MySQL service takes too long to start, you may need to increase this value. A value of 0 means there is no timeout.

  • --socket=path

    Property Value
    Command-Line Format --socket={file_name|pipe_name}
    System Variable socket
    Scope Global
    Dynamic No
    Type String
    Default Value (Other) /tmp/mysql.sock
    Default Value (Windows) MySQL

    On Unix, this option specifies the Unix socket file to use when listening for local connections. The default value is /tmp/mysql.sock. If this option is given, the server creates the file in the data directory unless an absolute path name is given to specify a different directory. On Windows, the option specifies the pipe name to use when listening for local connections that use a named pipe. The default value is MySQL (not case-sensitive).

  • --sql-mode=value[,value[,value...]]

    Property Value
    Command-Line Format --sql-mode=name
    System Variable sql_mode
    Scope Global, Session
    Dynamic Yes
    Type Set
    Default Value (>= 5.6.6) NO_ENGINE_SUBSTITUTION
    Default Value (<= 5.6.5) ''
    Valid Values

    ALLOW_INVALID_DATES

    ANSI_QUOTES

    ERROR_FOR_DIVISION_BY_ZERO

    HIGH_NOT_PRECEDENCE

    IGNORE_SPACE

    NO_AUTO_CREATE_USER

    NO_AUTO_VALUE_ON_ZERO

    NO_BACKSLASH_ESCAPES

    NO_DIR_IN_CREATE

    NO_ENGINE_SUBSTITUTION

    NO_FIELD_OPTIONS

    NO_KEY_OPTIONS

    NO_TABLE_OPTIONS

    NO_UNSIGNED_SUBTRACTION

    NO_ZERO_DATE

    NO_ZERO_IN_DATE

    ONLY_FULL_GROUP_BY

    PAD_CHAR_TO_FULL_LENGTH

    PIPES_AS_CONCAT

    REAL_AS_FLOAT

    STRICT_ALL_TABLES

    STRICT_TRANS_TABLES

    Set the SQL mode. The default is NO_ENGINE_SUBSTITUTION. See Section 5.1.10, “Server SQL Modes”.

    Note

    MySQL installation programs may configure the SQL mode during the installation process. For example, mysql_install_db creates a default option file named my.cnf in the base installation directory. This file contains a line that sets the SQL mode; see Section 4.4.3, “mysql_install_db — Initialize MySQL Data Directory”.

    If the SQL mode differs from the default or from what you expect, check for a setting in an option file that the server reads at startup.

  • --ssl*

    Options that begin with --ssl specify whether to permit clients to connect using SSL and indicate where to find SSL keys and certificates. See Command Options for Encrypted Connections.

  • --standalone

    Property Value
    Command-Line Format --standalone
    Platform Specific Windows

    Available on Windows only; instructs the MySQL server not to run as a service.

  • --super-large-pages

    Property Value
    Command-Line Format --super-large-pages[={OFF|ON}]
    Platform Specific Solaris
    Type Boolean
    Default Value OFF

    Standard use of large pages in MySQL attempts to use the largest size supported, up to 4MB. Under Solaris, a “super large pages” feature enables uses of pages up to 256MB. This feature is available for recent SPARC platforms. It can be enabled or disabled by using the --super-large-pages or --skip-super-large-pages option.

  • --symbolic-links, --skip-symbolic-links

    Property Value
    Command-Line Format --symbolic-links[={OFF|ON}]
    Type Boolean
    Default Value ON

    Enable or disable symbolic link support. This option has different effects on Windows and Unix:

  • --sysdate-is-now

    Property Value
    Command-Line Format --sysdate-is-now[={OFF|ON}]
    Type Boolean
    Default Value OFF

    SYSDATE() by default returns the time at which it executes, not the time at which the statement in which it occurs begins executing. This differs from the behavior of NOW(). This option causes SYSDATE() to be an alias for NOW(). For information about the implications for binary logging and replication, see the description for SYSDATE() in Section 12.6, “Date and Time Functions” and for SET TIMESTAMP in Section 5.1.7, “Server System Variables”.

  • --tc-heuristic-recover={COMMIT|ROLLBACK}

    Property Value
    Command-Line Format --tc-heuristic-recover=name
    Type Enumeration
    Default Value COMMIT
    Valid Values

    COMMIT

    ROLLBACK

    The type of decision to use in the heuristic recovery process. To use this option, two or more storage engines that support XA transactions must be installed.

  • --temp-pool

    Property Value
    Command-Line Format --temp-pool[={OFF|ON}]
    Type Boolean
    Default Value (Other) OFF
    Default Value (Linux) ON

    This option is ignored except on Linux. On Linux, it causes most temporary files created by the server to use a small set of names, rather than a unique name for each new file. This works around a problem in the Linux kernel dealing with creating many new files with different names. With the old behavior, Linux seems to “leak” memory, because it is being allocated to the directory entry cache rather than to the disk cache.

  • --transaction-isolation=level

    Property Value
    Command-Line Format --transaction-isolation=name
    Type Enumeration
    Default Value REPEATABLE-READ
    Valid Values

    READ-UNCOMMITTED

    READ-COMMITTED

    REPEATABLE-READ

    SERIALIZABLE

    Sets the default transaction isolation level. The level value can be READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See Section 13.3.6, “SET TRANSACTION Statement”.

    The default transaction isolation level can also be set at runtime using the SET TRANSACTION statement or by setting the tx_isolation system variable.

  • --transaction-read-only

    Property Value
    Command-Line Format --transaction-read-only[={OFF|ON}]
    Introduced 5.6.5
    Type Boolean
    Default Value OFF

    Sets the default transaction access mode. By default, read-only mode is disabled, so the mode is read/write.

    To set the default transaction access mode at runtime, use the SET TRANSACTION statement or set the tx_read_only system variable. See Section 13.3.6, “SET TRANSACTION Statement”.

  • --tmpdir=dir_name, -t dir_name

    Property Value
    Command-Line Format --tmpdir=dir_name
    System Variable tmpdir
    Scope Global
    Dynamic No
    Type Directory name

    The path of the directory to use for creating temporary files. It might be useful if your default /tmp directory resides on a partition that is too small to hold temporary tables. This option accepts several paths that are used in round-robin fashion. Paths should be separated by colon characters (:) on Unix and semicolon characters (;) on Windows.

    --tmpdir can be a non-permanent location, such as a directory on a memory-based file system or a directory that is cleared when the server host restarts. If the MySQL server is acting as a replication slave, and you are using a non-permanent location for --tmpdir, consider setting a different temporary directory for the slave using the slave_load_tmpdir system variable. For a replication slave, the temporary files used to replicate LOAD DATA statements are stored in this directory, so with a permanent location they can survive machine restarts, although replication can now continue after a restart if the temporary files have been removed.

    For more information about the storage location of temporary files, see Section B.4.3.5, “Where MySQL Stores Temporary Files”.

  • --user={user_name|user_id}, -u {user_name|user_id}

    Property Value
    Command-Line Format --user=name
    Type String

    Run the mysqld server as the user having the name user_name or the numeric user ID user_id. (“User” in this context refers to a system login account, not a MySQL user listed in the grant tables.)

    This option is mandatory when starting mysqld as root. The server changes its user ID during its startup sequence, causing it to run as that particular user rather than as root. See Section 6.1.1, “Security Guidelines”.

    To avoid a possible security hole where a user adds a --user=root option to a my.cnf file (thus causing the server to run as root), mysqld uses only the first --user option specified and produces a warning if there are multiple --user options. Options in /etc/my.cnf and $MYSQL_HOME/my.cnf are processed before command-line options, so it is recommended that you put a --user option in /etc/my.cnf and specify a value other than root. The option in /etc/my.cnf is found before any other --user options, which ensures that the server runs as a user other than root, and that a warning results if any other --user option is found.

  • --verbose, -v

    Use this option with the --help option for detailed help.

  • --version, -V

    Display version information and exit.


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