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MySQL 8.0 Reference Manual  /  ...  /  Server Command Options

7.1.7 Server Command Options

When you start the mysqld server, you can specify program options using any of the methods described in Section 6.2.2, “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 6.2.2.2, “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.

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 adjusts a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server sets 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 is 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, --sort_buffer_size=384M sets the sort_buffer_size variable to a value of 384MB.

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 15.7.6.1, “SET Syntax for Variable Assignment”.

Section 7.1.8, “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 7.1.1, “Configuring the Server”.

  • --help, -?

    Command-Line Format --help

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

  • --admin-ssl, --skip-admin-ssl

    Command-Line Format --admin-ssl[={OFF|ON}]
    Introduced 8.0.21
    Deprecated 8.0.26
    Type Boolean
    Default Value ON

    The --admin-ssl option is like the --ssl option, except that it applies to the administrative connection interface rather than the main connection interface. For information about these interfaces, see Section 7.1.12.1, “Connection Interfaces”.

    The --admin-ssl option specifies that the server permits but does not require encrypted connections on the administrative interface. This option is enabled by default.

    --admin-ssl can be specified in negated form as --skip-admin-ssl or a synonym (--admin-ssl=OFF, --disable-admin-ssl). In this case, the option specifies that the server does not permit encrypted connections, regardless of the settings of the admin_tsl_xxx and admin_ssl_xxx system variables.

    The --admin-ssl option has an effect only at server startup on whether the administrative interface supports encrypted connections. It is ignored and has no effect on the operation of ALTER INSTANCE RELOAD TLS at runtime. For example, you can use --admin-ssl=OFF to start the administrative interface with encrypted connections disabled, then reconfigure TLS and execute ALTER INSTANCE RELOAD TLS FOR CHANNEL mysql_admin to enable encrypted connections at runtime.

    For general information about configuring connection-encryption support, see Section 8.3.1, “Configuring MySQL to Use Encrypted Connections”. That discussion is written for the main connection interface, but the parameter names are similar for the administrative connection interface. Consider setting at least the admin_ssl_cert and admin_ssl_key system variables on the server side and the --ssl-ca (or --ssl-capath) option on the client side. For additional information specifically about the administrative interface, see Administrative Interface Support for Encrypted Connections.

    Because support for encrypted connections is enabled by default, it is normally unnecessary to specify --admin-ssl. As of MySQL 8.0.26, --admin-ssl is deprecated and subject to removal in a future MySQL version. If it is desired to disable encrypted connections, that can be done without specifying --admin-ssl in negated form. Set the admin_tls_version system variable to the empty value to indicate that no TLS versions are supported. For example, these lines in the server my.cnf file disable encrypted connections: 

    [mysqld]
admin_tls_version=''

  • --allow-suspicious-udfs

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

    This option controls whether loadable functions that have only an xxx symbol for the main function can be loaded. By default, the option is off and only loadable functions 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 functions. See Loadable Function Security Precautions.

  • --ansi

    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 1.6, “MySQL Standards Compliance”, and Section 7.1.11, “Server SQL Modes”.

  • --basedir=dir_name, -b dir_name

    Command-Line Format --basedir=dir_name
    System Variable basedir
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Directory name
    Default Value parent of mysqld installation directory

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

    The server executable determines its own full path name at startup and uses the parent of the directory in which it is located as the default basedir value. This in turn enables the server to use that basedir when searching for server-related information such as the share directory containing error messages.

  • --character-set-client-handshake

    Command-Line Format --character-set-client-handshake[={OFF|ON}]
    Deprecated 8.0.35
    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 option is deprecated in MySQL 8.0.35 and later MySQL 8.0 releases, where a warning is issued whenever it is used, and is to be removed in a future version of MySQL. Applications which depen on this option should begin migration away from it as soon as possible.

  • --chroot=dir_name, -r dir_name

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

  • --console

    Command-Line Format --console
    Platform Specific Windows

    (Windows only.) Cause the default error log destination to be the console. This affects log sinks that base their own output destination on the default destination. See Section 7.4.2, “The Error Log”. mysqld does not close the console window if this option is used.

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

  • --core-file

    Command-Line Format --core-file

    When this option is used, write a core file if mysqld dies; no arguments are needed (or accepted). 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 6.3.2, “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.

    The innodb_buffer_pool_in_core_file variable can be used to reduce the size of core files on operating systems that support it. For more information, see Section 17.8.3.7, “Excluding Buffer Pool Pages from Core Files”.

  • --daemonize, -D

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

    This option causes the server to run as a traditional, forking daemon, permitting it to work with operating systems that use systemd for process control. For more information, see Section 2.5.9, “Managing MySQL Server with systemd”.

    --daemonize is mutually exclusive with --initialize and --initialize-insecure.

    If the server is started using the --daemonize option and is not connected to a tty device, a default error logging option of --log-error="" is used in the absence of an explicit logging option, to direct error output to the default log file.

    -D is a synonym for --daemonize.

  • --datadir=dir_name, -h dir_name

    Command-Line Format --datadir=dir_name
    System Variable datadir
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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]

    Command-Line Format --debug[=debug_options]
    System Variable debug
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type String
    Default Value (Unix) d:t:i:o,/tmp/mysqld.trace
    Default Value (Windows) d:t:i:O,\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 7.9.4, “The DBUG Package”.

  • --debug-sync-timeout[=N]

    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 -DWITH_DEBUG=ON CMake option (see Section 2.8.7, “MySQL Source-Configuration Options”); otherwise, 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-time-zone=timezone

    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.

    The system_time_zone variable differs from time_zone. Although they might have the same value, the latter variable is used to initialize the time zone for each client that connects. See Section 7.1.15, “MySQL Server Time Zone Support”.

  • --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. If file_name is not an absolute path name, it is interpreted relative to the current directory. 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 6.2.2.3, “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. If file_name is not an absolute path name, it is interpreted relative to the current directory.

    Exception: Even with --defaults-file, mysqld reads mysqld-auto.cnf.

    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 6.2.2.3, “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 this option is given as --defaults-group-suffix=_other, mysqld also reads the [mysqld_other] group.

    For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --early-plugin-load=plugin_list

    Command-Line Format --early-plugin-load=plugin_list
    Type String
    Default Value empty string

    This option tells the server which plugins to load before loading mandatory built-in plugins and before storage engine initialization. Early loading is supported only for plugins compiled with PLUGIN_OPT_ALLOW_EARLY. If multiple --early-plugin-load options are given, only the last one applies.

    The option value is a semicolon-separated list of plugin_library and name=plugin_library values. Each plugin_library is the name of a library file that contains plugin code, and each name is the name of a plugin to load. If a plugin library is named without any preceding plugin name, the server loads all plugins in the library. With a preceding plugin name, the server loads only the named plugin from 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 are contained in the plugin library files myplug1.so and myplug2.so, use this option to perform an early plugin load: 

    mysqld --early-plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"

    Quotes surround the argument value because otherwise some command interpreters interpret semicolon (;) as a special character. (For example, Unix shells treat it as a command terminator.)

    Each named plugin is loaded early for a single invocation of mysqld only. After a restart, the plugin is not loaded early unless --early-plugin-load is used again.

    If the server is started using --initialize or --initialize-insecure, plugins specified by --early-plugin-load are not loaded.

    If the server is run with --help, plugins specified by --early-plugin-load are loaded but not initialized. This behavior ensures that plugin options are displayed in the help message.

    InnoDB tablespace encryption relies on the MySQL Keyring for encryption key management, and the keyring plugin to be used must be loaded prior to storage engine initialization to facilitate InnoDB recovery for encrypted tables. For example, administrators who want the keyring_file plugin loaded at startup should use --early-plugin-load with the appropriate option value (such as keyring_file.so on Unix and Unix-like systems or keyring_file.dll on Windows).

    For information about InnoDB tablespace encryption, see Section 17.13, “InnoDB Data-at-Rest Encryption”. For general information about plugin loading, see Section 7.6.1, “Installing and Uninstalling Plugins”.

    Note

    For MySQL Keyring, this option is used only when the keystore is managed with a keyring plugin. If keystore management uses a keyring component rather than a plugin, specify component loading using a manifest file; see Section 8.4.4.2, “Keyring Component Installation”.

  • --exit-info[=flags], -T [flags]

    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

    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 10.11.5, “External Locking”.

  • --flush

    Command-Line Format --flush[={OFF|ON}]
    System Variable flush
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    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.3.3.3, “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

    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 7.9.1.4, “Debugging mysqld under gdb”.

    On Windows, this option also suppresses the forking that is used to implement the RESTART statement: Forking enables one process to act as a monitor to the other, which acts as the server. However, forking makes determining the server process to attach to for debugging more difficult, so starting the server with --gdb suppresses forking. For a server started with this option, RESTART simply exits and does not restart.

    In non-debug settings, --no-monitor may be used to suppress forking the monitor process.

  • --initialize, -I

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

    This option is used to initialize a MySQL installation by creating the data directory and populating the tables in the mysql system schema. For more information, see Section 2.9.1, “Initializing the Data Directory”.

    This option limits the effects of, or is not compatible with, a number of other startup options for the MySQL server. Some of the most common issues of this sort are noted here:

    • We strongly recommend, when initializing the data directory with --initialize, that you specify no additional options other than --datadir, other options used for setting directory locations such as --basedir, and possibly --user, if required. Options for the running MySQL server can be specified when starting it once initialization has been completed and mysqld has shut down. This also applies when using --initialize-insecure instead of --initialize.

    • When the server is started with --initialize, 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. In addition, the disabled_storage_engines system variable has no effect.

    • The --ndbcluster option is ignored when used together with --initialize.

    • --initialize is mutually exclusive with --bootstrap and --daemonize.

    The items in the preceding list also apply when initializing the server using the --initialize-insecure option.

  • --initialize-insecure

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

    This option is used to initialize a MySQL installation by creating the data directory and populating the tables in the mysql system schema. This option implies --initialize, and the same restrictions and limitations apply; for more information, see the description of that option, and Section 2.9.1, “Initializing the Data Directory”.

    Warning

    This option creates a MySQL root user with an empty password, which is insecure. For this reason, do not use it in production without setting this password manually. See Post-Initialization root Password Assignment, for information about how to do this.

  • --innodb-xxx

    Set an option for the InnoDB storage engine. The InnoDB options are listed in Section 17.14, “InnoDB Startup Options and System Variables”.

  • --install [service_name]

    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 2.3.4.8, “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]

    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 2.3.4.8, “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

    Command-Line Format --language=name
    Deprecated Yes; use lc-messages-dir instead
    System Variable language
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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 12.12, “Setting the Error Message Language”.

    --lc-messages-dir and --lc-messages should be used rather than --language, which is deprecated (and handled as a synonym for --lc-messages-dir). You should expect the --language option to be removed in a future MySQL release.

  • --large-pages

    Command-Line Format --large-pages[={OFF|ON}]
    System Variable large_pages
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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 10.12.3.3, “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

    Command-Line Format --lc-messages=name
    System Variable lc_messages
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    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 12.12, “Setting the Error Message Language”.

  • --lc-messages-dir=dir_name

    Command-Line Format --lc-messages-dir=dir_name
    System Variable lc_messages_dir
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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 12.12, “Setting the Error Message Language”.

  • --local-service

    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 2.3.4.8, “Starting MySQL as a Windows Service”.

  • --log-error[=file_name]

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

    Set the default error log destination to the named file. This affects log sinks that base their own output destination on the default destination. See Section 7.4.2, “The Error Log”.

    If the option names no file, the default error log destination on Unix and Unix-like systems is a file named host_name.err in the data directory. The default destination 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 default destination is that file (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.

    If error log output cannot be redirected to the error log file, an error occurs and startup fails.

    On Windows, --console takes precedence over --log-error if both are given. In this case, the default error log destination is the console rather than a file.

  • --log-isam[=file_name]

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

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

  • --log-raw

    Command-Line Format --log-raw[={OFF|ON}]
    System Variable (≥ 8.0.19) log_raw
    Scope (≥ 8.0.19) Global
    Dynamic (≥ 8.0.19) Yes
    SET_VAR Hint Applies (≥ 8.0.19) No
    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.

    If a query rewrite plugin is installed, the --log-raw option affects statement logging as follows:

    • Without --log-raw, the server logs the statement returned by the query rewrite plugin. This may differ from the statement as received.

    • With --log-raw, the server logs the original statement as received.

    For more information, see Section 8.1.2.3, “Passwords and Logging”.

  • --log-short-format

    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-tc=file_name

    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

    Command-Line Format --log-tc-size=#
    Type Integer
    Default Value 6 * page size
    Minimum Value 6 * page size
    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 and minimum values are 6 times the page size, and the value must be a multiple of the page size.

  • --memlock

    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: 

    $> 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 8.1.5, “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 10.12.3.3, “Enabling Large Page Support”.

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

  • --myisam-block-size=N

    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 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --no-dd-upgrade

    Command-Line Format --no-dd-upgrade[={OFF|ON}]
    Deprecated 8.0.16
    Type Boolean
    Default Value OFF
    Note

    This option is deprecated as of MySQL 8.0.16. It is superseded by the --upgrade option, which provides finer control over data dictionary and server upgrade behavior.

    Prevent automatic upgrade of the data dictionary tables during the MySQL server startup process. This option is typically used when starting the MySQL server following an in-place upgrade of an existing installation to a newer MySQL version, which may include changes to data dictionary table definitions.

    When --no-dd-upgrade is specified, and the server finds that its expected version of the data dictionary differs from the version stored in the data dictionary itself, startup fails with an error stating that data dictionary upgrade is prohibited; 

    [ERROR] [MY-011091] [Server] Data dictionary upgrade prohibited by the
command line option '--no_dd_upgrade'.
[ERROR] [MY-010020] [Server] Data Dictionary initialization failed.

    During a normal startup, the data dictionary version of the server is compared to the version stored in the data dictionary to determine whether data dictionary table definitions should be upgraded. If an upgrade is necessary and supported, the server creates data dictionary tables with updated definitions, copies persisted metadata to the new tables, atomically replaces the old tables with the new ones, and reinitializes the data dictionary. If an upgrade is not necessary, startup continues without updating data dictionary tables.

  • --no-monitor

    Command-Line Format --no-monitor[={OFF|ON}]
    Introduced 8.0.12
    Platform Specific Windows
    Type Boolean
    Default Value OFF

    (Windows only). This option suppresses the forking that is used to implement the RESTART statement: Forking enables one process to act as a monitor to the other, which acts as the server. For a server started with this option, RESTART simply exits and does not restart.

    --no-monitor is not available prior to MySQL 8.0.12. The --gdb option can be used as a workaround.

  • --old-style-user-limits

    Command-Line Format --old-style-user-limits[={OFF|ON}]
    Deprecated 8.0.30
    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 8.2.21, “Setting Account Resource Limits”.

    This option is deprecated, and, as of MySQL 8.0.30, using it on the command line or in an option file causes MySQL to raise a warning. Expect this option to be removed in a future release; you should check your applications now for use of --old-style-user-limits and remove any dependencies they might have on it, before this happens.

  • --performance-schema-xxx

    Configure a Performance Schema option. For details, see Section 29.14, “Performance Schema Command Options”.

  • --plugin-load=plugin_list

    Command-Line Format --plugin-load=plugin_list
    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 applies. Additional plugins to load may be specified using --plugin-load-add options.

    The option value is a semicolon-separated list of plugin_library and name=plugin_library values. Each plugin_library is the name of a library file that contains plugin code, and each name is the name of a plugin to load. If a plugin library is named without any preceding plugin name, the server loads all plugins in the library. With a preceding plugin name, the server loads only the named plugin from 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 are contained in the plugin library files myplug1.so and myplug2.so, use this option to perform an early plugin load: 

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

    Quotes surround the argument value because otherwise some command interpreters interpret semicolon (;) as a special character. (For example, Unix shells treat it as a command terminator.)

    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.

    During the normal startup sequence, 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, plugins registered in the mysql.plugins table are not loaded and are unavailable. --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.

    This option does not set a corresponding system variable. The output of SHOW PLUGINS provides information about loaded plugins. More detailed information can be found in the Information Schema PLUGINS table. See Section 7.6.2, “Obtaining Server Plugin Information”.

    For additional information about plugin loading, see Section 7.6.1, “Installing and Uninstalling Plugins”.

  • --plugin-load-add=plugin_list

    Command-Line Format --plugin-load-add=plugin_list
    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

    This option does not set a corresponding system variable. The output of SHOW PLUGINS provides information about loaded plugins. More detailed information can be found in the Information Schema PLUGINS table. See Section 7.6.2, “Obtaining Server Plugin Information”.

    For additional information about plugin loading, see Section 7.6.1, “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 6.2.2.4, “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

    Command-Line Format --port=port_num
    System Variable port
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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

    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. Password values are masked. 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 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --remove [service_name]

    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 2.3.4.8, “Starting MySQL as a Windows Service”.

  • --safe-user-create

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

    This option is deprecated, and ignored as of MySQL 8.0.11. For related information, see Server Changes.

    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

    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 schema, and thus to start without using the privilege system at all. This gives anyone with access to the server unrestricted access to all databases.

      Because starting the server with --skip-grant-tables disables authentication checks, the server also disables remote connections in that case by enabling skip_networking.

      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, the server flushes the privileges if it performs an upgrade during the startup sequence.

    • --skip-grant-tables disables failed-login tracking and temporary account locking because those capabilities depend on the grant tables. See Section 8.2.15, “Password Management”.

    • --skip-grant-tables causes the server not to load certain other objects registered in the data dictionary or the mysql system schema:

      --skip-grant-tables does not suppress loading during startup of components.

    • --skip-grant-tables causes the disabled_storage_engines system variable to have no effect.

  • --skip-host-cache

    Command-Line Format --skip-host-cache
    Deprecated 8.0.30

    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.

    Beginning with MySQL 8.0.30, this option is deprecated; you should use SET GLOBAL host_cache_size = 0 instead.

    Starting the server with --skip-host-cache does not prevent runtime 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 7.1.12.3, “DNS Lookups and the Host Cache”.

  • --skip-innodb

    Disable the InnoDB storage engine. In this case, because the default storage engine is InnoDB, the server does 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.

    The InnoDB storage engine cannot be disabled, and the --skip-innodb option is deprecated and has no effect. Its use results in a warning. Expect this option to be removed in a future MySQL release.

  • --skip-new

    Command-Line Format --skip-new
    Deprecated 8.0.35

    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.

    This option is deprecated as of MySQL 8.0.35, and is subject to removal in a future release.

  • --skip-show-database

    Command-Line Format --skip-show-database
    System Variable skip_show_database
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    This option sets the skip_show_database system variable that controls who is permitted to use the SHOW DATABASES statement. See Section 7.1.8, “Server System Variables”.

  • --skip-stack-trace

    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 7.9, “Debugging MySQL”.

  • --slow-start-timeout=timeout

    Command-Line Format --slow-start-timeout=#
    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

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

    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...]]

    Command-Line Format --sql-mode=name
    System Variable sql_mode
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies Yes
    Type Set
    Default Value ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_ZERO_IN_DATE NO_ZERO_DATE ERROR_FOR_DIVISION_BY_ZERO NO_ENGINE_SUBSTITUTION
    Valid Values

    ALLOW_INVALID_DATES

    ANSI_QUOTES

    ERROR_FOR_DIVISION_BY_ZERO

    HIGH_NOT_PRECEDENCE

    IGNORE_SPACE

    NO_AUTO_VALUE_ON_ZERO

    NO_BACKSLASH_ESCAPES

    NO_DIR_IN_CREATE

    NO_ENGINE_SUBSTITUTION

    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

    TIME_TRUNCATE_FRACTIONAL

    Set the SQL mode. See Section 7.1.11, “Server SQL Modes”.

    Note

    MySQL installation programs may configure the SQL mode during the installation process.

    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, --skip-ssl

    Command-Line Format --ssl[={OFF|ON}]
    Deprecated 8.0.26
    Disabled by skip-ssl
    Type Boolean
    Default Value ON

    The --ssl option specifies that the server permits but does not require encrypted connections on the main connection interface. This option is enabled by default.

    A similar option, --admin-ssl, is like the --ssl, except that it applies to the administrative connection interface rather than the main connection interface. For information about these interfaces, see Section 7.1.12.1, “Connection Interfaces”.

    --ssl can be specified in negated form as --skip-ssl or a synonym (--ssl=OFF, --disable-ssl). In this case, the option specifies that the server does not permit encrypted connections, regardless of the settings of the tls_xxx and ssl_xxx system variables.

    The --ssl option has an effect only at server startup on whether the server supports encrypted connections. It is ignored and has no effect on the operation of ALTER INSTANCE RELOAD TLS at runtime. For example, you can use --ssl=OFF to start the server with encrypted connections disabled, then reconfigure TLS and execute ALTER INSTANCE RELOAD TLS to enable encrypted connections at runtime.

    For more information about configuring whether the server permits clients to connect using SSL and indicating where to find SSL keys and certificates, see Section 8.3.1, “Configuring MySQL to Use Encrypted Connections”, which also describes server capabilities for certificate and key file autogeneration and autodiscovery. Consider setting at least the ssl_cert and ssl_key system variables on the server side and the --ssl-ca (or --ssl-capath) option on the client side.

    Because support for encrypted connections is enabled by default, it is normally unnecessary to specify --ssl. As of MySQL 8.0.26, --ssl is deprecated and subject to removal in a future MySQL version. If it is desired to disable encrypted connections, that can be done without specifying --ssl in negated form. Set the tls_version system variable to the empty value to indicate that no TLS versions are supported. For example, these lines in the server my.cnf file disable encrypted connections: 

    [mysqld]
tls_version=''

  • --standalone

    Command-Line Format --standalone
    Platform Specific Windows

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

  • --super-large-pages

    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

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

    Enable or disable symbolic link support. On Unix, enabling symbolic links means that you can link a MyISAM index file or data file to another directory with the INDEX DIRECTORY or DATA DIRECTORY option of the CREATE TABLE statement. If you delete or rename the table, the files that its symbolic links point to also are deleted or renamed. See Section 10.12.2.2, “Using Symbolic Links for MyISAM Tables on Unix”.

    Note

    Symbolic link support, along with the --symbolic-links option that controls it, is deprecated; you should expect it to be removed in a future version of MySQL. In addition, the option is disabled by default. The related have_symlink system variable also is deprecated; expect it to be removed in a future version of MySQL.

    This option has no meaning on Windows.

  • --sysdate-is-now

    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 a synonym for NOW(). For information about the implications for binary logging and replication, see the description for SYSDATE() in Section 14.7, “Date and Time Functions” and for SET TIMESTAMP in Section 7.1.8, “Server System Variables”.

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

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

    OFF

    COMMIT

    ROLLBACK

    The decision to use in a manual heuristic recovery.

    If a --tc-heuristic-recover option is specified, the server exits regardless of whether manual heuristic recovery is successful.

    On systems with more than one storage engine capable of two-phase commit, the ROLLBACK option is not safe and causes recovery to halt with the following error: 

    [ERROR] --tc-heuristic-recover rollback
strategy is not safe on systems with more than one 2-phase-commit-capable
storage engine. Aborting crash recovery.

  • --transaction-isolation=level

    Command-Line Format --transaction-isolation=name
    System Variable transaction_isolation
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    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 15.3.7, “SET TRANSACTION Statement”.

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

  • --transaction-read-only

    Command-Line Format --transaction-read-only[={OFF|ON}]
    System Variable transaction_read_only
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    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 transaction_read_only system variable. See Section 15.3.7, “SET TRANSACTION Statement”.

  • --tmpdir=dir_name, -t dir_name

    Command-Line Format --tmpdir=dir_name
    System Variable tmpdir
    Scope Global
    Dynamic No
    SET_VAR Hint Applies 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 replica, and you are using a non-permanent location for --tmpdir, consider setting a different temporary directory for the replica using the replica_load_tmpdir or slave_load_tmpdir system variable. For a replica, 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.3.3.5, “Where MySQL Stores Temporary Files”.

  • --upgrade=value

    Command-Line Format --upgrade=value
    Introduced 8.0.16
    Type Enumeration
    Default Value AUTO
    Valid Values

    AUTO

    NONE

    MINIMAL

    FORCE

    This option controls whether and how the server performs an automatic upgrade at startup. Automatic upgrade involves two steps:

    • Step 1: Data dictionary upgrade.

      This step upgrades:

      • The data dictionary tables in the mysql schema. If the actual data dictionary version is lower than the current expected version, the server upgrades the data dictionary. If it cannot, or is prevented from doing so, the server cannot run.

      • The Performance Schema and INFORMATION_SCHEMA.

    • Step 2: Server upgrade.

      This step comprises all other upgrade tasks. If the existing installation data has a lower MySQL version than the server expects, it must be upgraded:

      • The system tables in the mysql schema (the remaining non-data dictionary tables).

      • The sys schema.

      • User schemas.

    For details about upgrade steps 1 and 2, see Section 3.4, “What the MySQL Upgrade Process Upgrades”.

    These --upgrade option values are permitted:

    • AUTO

      The server performs an automatic upgrade of anything it finds to be out of date (steps 1 and 2). This is the default action if --upgrade is not specified explicitly.

    • NONE

      The server performs no automatic upgrade steps during the startup process (skips steps 1 and 2). Because this option value prevents a data dictionary upgrade, the server exits with an error if the data dictionary is found to be out of date: 

      [ERROR] [MY-013381] [Server] Server shutting down because upgrade is
required, yet prohibited by the command line option '--upgrade=NONE'.
[ERROR] [MY-010334] [Server] Failed to initialize DD Storage Engine
[ERROR] [MY-010020] [Server] Data Dictionary initialization failed.

    • MINIMAL

      The server upgrades the data dictionary, the Performance Schema, and the INFORMATION_SCHEMA, if necessary (step 1). Note that following an upgrade with this option, Group Replication cannot be started, because system tables on which the replication internals depend are not updated, and reduced functionality might also be apparent in other areas.

    • FORCE

      The server upgrades the data dictionary, the Performance Schema, and the INFORMATION_SCHEMA, if necessary (step 1). In addition, the server forces an upgrade of everything else (step 2). Expect server startup to take longer with this option because the server checks all objects in all schemas.

      FORCE is useful to force step 2 actions to be performed if the server thinks they are not necessary. For example, you may believe that a system table is missing or has become damaged and want to force a repair.

    The following table summarizes the actions taken by the server for each option value.

    Option Value Server Performs Step 1? Server Performs Step 2?
    AUTO If necessary If necessary
    NONE No No
    MINIMAL If necessary No
    FORCE If necessary Yes

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

    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 8.1.1, “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.

  • --validate-config

    Command-Line Format --validate-config[={OFF|ON}]
    Introduced 8.0.16
    Type Boolean
    Default Value OFF

    Validate the server startup configuration. If no errors are found, the server terminates with an exit code of 0. If an error is found, the server displays a diagnostic message and terminates with an exit code of 1. Warning and information messages may also be displayed, depending on the log_error_verbosity value, but do not produce immediate validation termination or an exit code of 1. For more information, see Section 7.1.3, “Server Configuration Validation”.

  • --validate-user-plugins[={OFF|ON}]

    Command-Line Format --validate-user-plugins[={OFF|ON}]
    Type Boolean
    Default Value ON

    If this option is enabled (the default), the server checks each user account and produces a warning if conditions are found that would make the account unusable:

    • The account requires an authentication plugin that is not loaded.

    • The account requires the sha256_password or caching_sha2_password authentication plugin but the server was started with neither SSL nor RSA enabled as required by the plugin.

    Enabling --validate-user-plugins slows down server initialization and FLUSH PRIVILEGES. If you do not require the additional checking, you can disable this option at startup to avoid the performance decrement.

  • --verbose, -v

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

  • --version, -V

    Display version information and exit.


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MySQL Replication
Using the MySQL Yum Repository
MySQL NDB Cluster 8.0