5.1.3. Server Command Options

When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.3, "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 4.2.3.3, "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 mysqld --help. To see the full list, use mysqld --verbose --help.

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

Options that affect security: See Section 6.1.4, "Security-Related mysqld Options and Variables".
SSL-related options: See Section 6.3.9.4, "SSL Command Options".
Binary log control options: See Section 5.2.4, "The Binary Log".
Replication-related options: See Section 16.1.4, "Replication and Binary Logging Options and Variables".
Options for loading plugins such as pluggable storage engines: See Section 5.1.8.1, "Installing and Uninstalling Plugins".
Options specific to particular storage engines: See Section 14.2.6, "InnoDB Startup Options and System Variables" and Section 14.3.1, "MyISAM Startup Options".

You can also set the values of server system variables by using variable names as options, as described at the end of this section.

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.

--help, -?

Command-Line Format	`-?`
	`--help`
Option-File Format	`help`

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

--allow-suspicious-udfs

Command-Line Format	`--allow-suspicious-udfs`
Option-File Format	`allow-suspicious-udfs`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

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 Section 23.3.2.6, "User-Defined Function Security Precautions".

--ansi

Command-Line Format	`--ansi`
	`-a`
Option-File 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 1.8.3, "Running MySQL in ANSI Mode", and Section 5.1.7, "Server SQL Modes".

--basedir=path, -b path

Command-Line Format	`--basedir=path`
	`-b`
Option-File Format	`basedir`
System Variable Name	`basedir`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`

The path to the MySQL installation directory. All paths are usually resolved relative to this directory.

--big-tables

Removed	5.6.1
Command-Line Format	`--big-tables`
Option-File Format	`big-tables`
System Variable Name	`big_tables`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`

Enable large result sets by saving all temporary sets in files. This option prevents most "table full" errors, but also slows down queries for which in-memory tables would suffice. Since MySQL 3.23.2, the server is able to handle large result sets automatically by using memory for small temporary tables and switching to disk tables where necessary.

--bind-address=addr

Command-Line Format	`--bind-address=addr`
Option-File Format	`bind-address`
System Variable Name	`bind_address`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values (<= 5.6.5)
	Type	`string`
	Default	`0.0.0.0`
	Permitted Values (>= 5.6.6)
	Type	`string`
	Default	`*`

The MySQL server listens on a single network socket for TCP/IP connections. This socket is bound to a single address, but it is possible for an address to map onto multiple network interfaces. To specify an address, use the --bind-address=addr option at server startup, where addr is an IPv4 or IPv6 address or a host name. If addr is a host name, the server resolves the name to an IP address and binds to that address.

The server treats different types of addresses as follows:

If the address is *, the server accepts TCP/IP connections on all server host IPv6 and IPv4 interfaces if the server host supports IPv6, or accepts TCP/IP connections on all IPv4 addresses otherwise. Use this address to permit both IPv4 and IPv6 connections on all server interfaces. This value is permitted (and is the default) as of MySQL 5.6.6.
If the address is 0.0.0.0, the server accepts TCP/IP connections on all server host IPv4 interfaces. This is the default before MySQL 5.6.6.
If the address is ::, the server accepts TCP/IP connections on all server host IPv4 and IPv6 interfaces.
If the address is an IPv4-mapped address, the server accepts TCP/IP connections for that address, in either IPv4 or IPv6 format. For example, if the server is bound to ::ffff:127.0.0.1, clients can connect using --host=127.0.0.1 or --host=::ffff:127.0.0.1.
If the address is a "regular" IPv4 or IPv6 address (such as 127.0.0.1 or ::1), the server accepts TCP/IP connections only for that IPv4 or IPv6 address.

If you intend to bind the server to a specific address, be sure that the mysql.user grant table contains an account with administrative privileges that you can use to connect to that address. Otherwise, you will not be able to shut down the server. For example, if you bind the server to *, you can connect to it using all existing accounts. But if you bind the server to ::1, it accepts connections only on that address. In that case, first make sure that the 'root'@'::1' account is present in the mysql.user table so you can still connect to the server to shut it down.

--binlog-format={ROW|STATEMENT|MIXED}

Command-Line Format	`--binlog-format=format`
Option-File Format	`binlog-format`
System Variable Name	`binlog_format`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`enumeration`
	Default	`STATEMENT`
	Valid Values	`ROW`
		`STATEMENT`
		`MIXED`

Specify whether to use row-based, statement-based, or mixed replication. Statement-based is the default in MySQL 5.6. See Section 16.1.2, "Replication Formats".

Under some conditions, changing this variable at runtime is not possible, or causes replication to fail. See Section 5.2.4.2, "Setting The Binary Log Format", for more information.

Setting the binary logging format without enabling binary logging sets the binlog_format global system variable and logs a warning.

--bootstrap

Command-Line Format	`--bootstrap`
Option-File Format	`bootstrap`

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

In MySQL 5.6.6 and later, replication and global transaction identifiers are automatically disabled whenever this option is used (Bug #1332602). See Section 16.1.3, "Replication with Global Transaction Identifiers".

--character-sets-dir=path

Command-Line Format	`--character-sets-dir=path`
Option-File Format	`character-sets-dir`
System Variable Name	`character_sets_dir`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`directory name`

The directory where character sets are installed. See Section 10.5, "Character Set Configuration".

--character-set-client-handshake

Command-Line Format	`--character-set-client-handshake`
Option-File Format	`character-set-client-handshake`
	Permitted Values
	Type	`boolean`
	Default	`TRUE`

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.

--character-set-filesystem=charset_name

Command-Line Format	`--character-set-filesystem=name`
Option-File Format	`character-set-filesystem`
System Variable Name	`character_set_filesystem`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`string`

The file system character set. This option sets the character_set_filesystem system variable.

--character-set-server=charset_name, -C charset_name

Command-Line Format	`--character-set-server`
Option-File Format	`character-set-server`
System Variable Name	`character_set_server`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`string`

Use charset_name as the default server character set. See Section 10.5, "Character Set Configuration". If you use this option to specify a nondefault character set, you should also use --collation-server to specify the collation.

--chroot=path, -r path

Command-Line Format	`--chroot=name`
	`-r name`
Option-File Format	`chroot`
	Permitted Values
	Type	`file name`

Put the mysqld server in a closed environment during startup by using the chroot() system call. This is a recommended security measure. Note that use of this option somewhat limits LOAD DATA INFILE and SELECT ... INTO OUTFILE.

--collation-server=collation_name

Command-Line Format	`--collation-server`
Option-File Format	`collation-server`
System Variable Name	`collation_server`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`string`

Use collation_name as the default server collation. See Section 10.5, "Character Set Configuration".

--console

Command-Line Format	`--console`
Option-File Format	`console`
Platform Specific	windows

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

If both --log-error and --console are specified, --log-error takes precedence. The server writes to the log file, but not to the console.

--core-file

Command-Line Format	`--core-file`
Option-File Format	`core-file`
	Permitted Values
	Type	`boolean`
	Default	`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 Mac OS X, 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=path, -h path

Command-Line Format	`--datadir=path`
	`-h`
Option-File Format	`datadir`
System Variable Name	`datadir`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`

The path to the data directory.

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

Command-Line Format	`--debug[=debug_options]`
Option-File Format	`debug`
System Variable Name	`debug`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`string`
	Default	`'d:t:o,/tmp/mysqld.trace'`

If MySQL is configured with -DWITH_DEBUG=1, 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,mysqld.trace'. See MySQL Internals: Porting to Other Systems.

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.

--debug-sync-timeout[=N]

Command-Line Format	`--debug-sync-timeout[=#]`
Option-File Format	`debug-sync-timeout`
	Permitted Values
	Type	`numeric`

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 option (see Section 2.9.4, "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

Introduced	5.6.6
Command-Line Format	`--default-authentication-plugin=plugin_name`
Option-File Format	`default-authentication-plugin`
	Permitted Values
	Type	`enumeration`
	Default	`mysql_native_password`
	Valid Values	`mysql_native_password`
		`sha256_password`

The default authentication plugin. Acceptable values are mysql_native_password (use MySQL native passwords) and sha256_password (use SHA-256 passwords). For more information about these plugins, see Section 6.3.7.1, "The Native Authentication Plugins", and Section 6.3.7.2, "The SHA-256 Authentication Plugin". This option was added in MySQL 5.6.6.

The value of this option affects these aspects of server operation:

It determines which plugin the server assigns to new accounts for which no plugin is explicitly specified.
It sets the old_passwords system variable at startup to the value that is consistent with the password hashing format required by the default plugin. This in turn affects the password hashing method used by the PASSWORD() function.
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 according to the value of old_passwords.
```
CREATE USER ... IDENTIFIED BY 'cleartext
                                password';GRANT ...  IDENTIFIED BY 'cleartext
                                password';
```
For an account created with either of the following statements, the statement fails if the password hash is not encrypted using the hash format required by the default authentication plugin. Otherwise, the server associates the account with the default authentication plugin and assigns the account the given password hash.
```
CREATE USER ... IDENTIFIED BY 'encrypted
                                password';GRANT ...  IDENTIFIED BY 'encrypted
                                password';
```
Note

If you use this option to change the default authentication method to a value other than mysql_native_password, clients older than MySQL 5.5.6 will no longer be able to connect because they will not understand the change to the authentication protocol.

--default-storage-engine=type

Command-Line Format	`--default-storage-engine=name`
Option-File Format	`default-storage-engine`
System Variable Name	`default_storage_engine`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`enumeration`
	Default	`InnoDB`

Set the default storage engine for tables. See Chapter 14, Storage Engines. As of MySQL 5.6.3, this option sets the storage engine for permanent tables only. To set the storage engine for TEMPORARY tables, set the default_tmp_storage_engine system variable.

If you disable the default storage engine at server startup, you must set the default engine for both permanent and TEMPORARY tables to a different engine or the server will not start.

--default-time-zone=timezone

Command-Line Format	`--default-time-zone=name`
Option-File Format	`default-time-zone`
	Permitted Values
	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.

--delay-key-write[={OFF|ON|ALL}]

Command-Line Format	`--delay-key-write[=name]`
Option-File Format	`delay-key-write`
System Variable Name	`delay_key_write`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`enumeration`
	Default	`ON`
	Valid Values	`ON`
		`OFF`
		`ALL`

Specify how to use delayed key writes. Delayed key writing causes key buffers not to be flushed between writes for MyISAM tables. OFF disables delayed key writes. ON enables delayed key writes for those tables that were created with the DELAY_KEY_WRITE option. ALL delays key writes for all MyISAM tables. See Section 8.11.2, "Tuning Server Parameters", and Section 14.3.1, "MyISAM Startup Options".

Note

If you set this variable to ALL, you should not use MyISAM tables from within another program (such as another MySQL server or myisamchk) when the tables are in use. Doing so leads to index corruption.

--des-key-file=file_name

Command-Line Format	`--des-key-file=file_name`
Option-File Format	`des-key-file`

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

--enable-named-pipe

Command-Line Format	`--enable-named-pipe`
Option-File Format	`enable-named-pipe`
Platform Specific	windows

Enable support for named pipes. This option applies only on Windows.

--engine-condition-pushdown={ON|OFF}

Deprecated	5.5.3, by optimizer_switch
Removed	5.6.1
Command-Line Format	`--engine-condition-pushdown`
Option-File Format	`engine-condition-pushdown`
System Variable Name	`engine_condition_pushdown`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`ON`

Formerly, this option set the engine_condition_pushdown system variable; the option and the variable were both removed in MySQL 5.6.1. For more information, see Section 8.13.3, "Engine Condition Pushdown Optimization".

--event-scheduler[=value]

Command-Line Format	`--event-scheduler[=value]`
Option-File Format	`event-scheduler`
System Variable Name	`event_scheduler`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`enumeration`
	Default	`OFF`
	Valid Values	`ON`
		`OFF`
		`DISABLED`

Enable or disable, and start or stop, the event scheduler.

For detailed information, see The --event-scheduler Option.

--exit-info[=flags], -T [flags]

Command-Line Format	`--exit-info[=flags]`
	`-T [flags]`
Option-File Format	`exit-info`
	Permitted Values
	Type	`numeric`

This is a bit mask 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`
Option-File Format	`external-locking`
Disabled by	`skip-external-locking`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

Enable external locking (system locking), which is disabled by default as of MySQL 4.0. Note that 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.

External locking affects only MyISAM table access. For more information, including conditions under which it can and cannot be used, see Section 8.10.5, "External Locking".

--flush

Command-Line Format	`--flush`
Option-File Format	`flush`
System Variable Name	`flush`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`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 C.5.4.2, "What to Do If MySQL Keeps Crashing".

--gdb

Command-Line Format	`--gdb`
Option-File Format	`gdb`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

Install an interrupt handler for SIGINT (needed to stop mysqld with ^C to set breakpoints) and disable stack tracing and core file handling. See MySQL Internals: Porting to Other Systems.

--general-log[={0|1}]

Command-Line Format	`--general-log`
Option-File Format	`general-log`
System Variable Name	`general_log`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`OFF`

Specify the initial general query log state. With no argument or an argument of 1, the --general-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

--ignore-db-dir=dir_name

Introduced	5.6.3
Command-Line Format	`--ignore-db-dir`
Option-File Format	`ignore-db-dir`
	Permitted Values
	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.

This option was added in MySQL 5.6.3.

--init-file=file_name

Command-Line Format	`--init-file=file_name`
Option-File Format	`init-file`
System Variable Name	`init_file`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`

Read SQL statements from this file at startup. Each statement must be on a single line and should not include comments.

--innodb-xxx

Set an option for the InnoDB storage engine. The InnoDB options are listed in Section 14.2.6, "InnoDB Startup Options and System Variables".

--install [service_name]

Command-Line Format --install [service_name]

(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 2.3.5.7, "Starting MySQL as a Windows Service".

--install-manual [service_name]

Command-Line Format --install-manual [service_name]

(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 2.3.5.7, "Starting MySQL as a Windows Service".

--language=lang_name, -L lang_name

Deprecated	5.6.1, by lc-messages-dir
Command-Line Format	`--language=name`
	`-L`
Option-File Format	`language`
System Variable Name	`language`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`directory name`
	Default	`/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 10.2, "Setting the Error Message Language".

In MySQL 5.6, --lc-messages-dir and --lc-messages should be used rather than --language, which is deprecated as of MySQL 5.6.1 and handled as an alias for --lc-messages-dir. The --language option will be removed in a future MySQL release.

--large-pages

Command-Line Format	`--large-pages`
Option-File Format	`large-pages`
System Variable Name	`large_pages`
Variable Scope	Global
Dynamic Variable	No
Platform Specific	linux
	Permitted Values
	Type (linux)	`boolean`
	Default	`FALSE`

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 5.6 supports the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.11.4.2, "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

Command-Line Format	`--lc-messages=name`
Option-File Format	`lc-messages`
System Variable Name	`lc_messages`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`string`

The locale to use for error messages. The server converts the argument to a language name and combines it with the value of the --lc-messages-dir to produce the location for the error message file. See Section 10.2, "Setting the Error Message Language".

--lc-messages-dir=path

Command-Line Format	`--lc-messages-dir=path`
Option-File Format	`lc-messages-dir`
System Variable Name	`lc_messages_dir`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`directory name`

The directory where error messages are located. The value is used together with the value of --lc-messages to produce the location for the error message file. See Section 10.2, "Setting the Error Message Language".

--log[=file_name], -l [file_name]

Deprecated	5.1.29, by general-log
Removed	5.6.1
Command-Line Format	`--log[=name]`
	`-l`
Option-File Format	`log`
System Variable Name	`log`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`string`
	Default	`OFF`

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

--log-error[=file_name]

Command-Line Format	`--log-error[=name]`
Option-File Format	`log-error`
System Variable Name	`log_error`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`

Log errors and startup messages to this file. See Section 5.2.2, "The Error Log". If you omit the file name, MySQL uses host_name.err. If the file name has no extension, the server adds an extension of .err.

--log-isam[=file_name]

Command-Line Format	`--log-isam[=name]`
Option-File Format	`log-isam`
	Permitted Values
	Type	`file name`

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

--log-output=value,...

Command-Line Format	`--log-output=name`
Option-File Format	`log-output`
System Variable Name	`log_output`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`set`
	Default	`FILE`
	Valid Values	`TABLE`
		`FILE`
		`NONE`

This option determines the destination for general query log and slow query log output. The option value can be given as one or more of the words TABLE, FILE, or NONE. TABLE select logging to the general_log and slow_log tables in the mysql database as a destination. FILE selects logging to log files as a destination. NONE disables logging. If NONE is present in the option value, it takes precedence over any other words that are present. TABLE and FILE can both be given to select to both log output destinations.

This option selects log output destinations, but does not enable log output. To do that, use the --general_log and --slow_query_log options. For FILE logging, the --general_log_file and -slow_query_log_file options determine the log file location. For more information, see Section 5.2.1, "Selecting General Query and Slow Query Log Output Destinations".

--log-queries-not-using-indexes

Command-Line Format	`--log-queries-not-using-indexes`
Option-File Format	`log-queries-not-using-indexes`
System Variable Name	`log_queries_not_using_indexes`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`OFF`

If you are using this option with the slow query log enabled, queries that are expected to retrieve all rows are logged. See Section 5.2.5, "The Slow Query Log". This option does not necessarily mean that no index is used. For example, a query that uses a full index scan uses an index but would be logged because the index would not limit the number of rows.

--log-raw

Introduced	5.6.3
Command-Line Format	`--log-raw[=value]`
Option-File Format	`log-raw`
	Permitted Values
	Type	`boolean`
	Default	`OFF`

As of MySQL 5.6.3, 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.

Before MySQL 5.6.3, passwords in statements are not rewritten and the general query log should be protected. See Section 6.1.2.3, "Passwords and Logging".

This option was added in MySQL 5.6.3.

--log-short-format

Command-Line Format	`--log-short-format`
Option-File Format	`log-short-format`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

Log less information to the binary log and slow query log, if they have been activated.

--log-slow-admin-statements

Removed	5.6.11
Command-Line Format	`--log-slow-admin-statements`	through 5.6.10
Option-File Format	`log-slow-admin-statements`
	Permitted Values
	Type	`boolean`
	Default	`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-slow-queries[=file_name]

Deprecated	5.1.29, by slow-query-log
Removed	5.6.1
Command-Line Format	`--log-slow-queries[=name]`
Option-File Format	`log-slow-queries`
System Variable Name	`log_slow_queries`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`

The --log-slow-queries option was removed in MySQL 5.6.1 (along with the log_slow_queries system variable). Instead, use the --slow_query_log option to enable the slow query log and the --slow_query_log_file=file_name option to set the slow query log file name.

--log-tc=file_name

Command-Line Format	`--log-tc=name`
Option-File Format	`log-tc`
	Permitted Values
	Type	`file name`
	Default	`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. Currently, this option is unused.

--log-tc-size=size

Command-Line Format	`--log-tc-size=#`
Option-File Format	`log-tc-size`
	Permitted Values
	Platform Bit Size	`32`
	Type	`numeric`
	Default	`24576`
	Max Value	`4294967295`
	Permitted Values
	Platform Bit Size	`64`
	Type	`numeric`
	Default	`24576`
	Max Value	`18446744073709547520`

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

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

Command-Line Format	`--log-warnings[=#]`
	`-W [#]`
Option-File Format	`log-warnings`
System Variable Name	`log_warnings`
Variable Scope	Global
Dynamic Variable	Yes
Disabled by	`skip-log-warnings`
	Permitted Values
	Platform Bit Size	`32`
	Type	`numeric`
	Default	`1`
	Range	`0 .. 4294967295`
	Permitted Values
	Platform Bit Size	`64`
	Type	`numeric`
	Default	`1`
	Range	`0 .. 18446744073709547520`

Print out warnings such as Aborted connection... to the error log. Enabling this option is recommended, for example, if you use replication (you get more information about what is happening, such as messages about network failures and reconnections). This option is enabled (1) by default, and the default level value if omitted is 1. To disable this option, use --log-warnings=0. 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 C.5.2.11, "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 only if --log-warnings is enabled.

--low-priority-updates

Command-Line Format	`--low-priority-updates`
Option-File Format	`low-priority-updates`
System Variable Name	`low_priority_updates`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower priority than selects. This can also be done using {INSERT | REPLACE | DELETE | UPDATE} LOW_PRIORITY ... to lower the priority of only one query, or by SET LOW_PRIORITY_UPDATES=1 to change the priority in one thread. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See Section 8.10.2, "Table Locking Issues".

--min-examined-row-limit=number

Command-Line Format	`--min-examined-row-limit=#`
Option-File Format	`min-examined-row-limit`
System Variable Name	`min_examined_row_limit`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Platform Bit Size	`32`
	Type	`numeric`
	Default	`0`
	Range	`0 .. 4294967295`
	Permitted Values
	Platform Bit Size	`64`
	Type	`numeric`
	Default	`0`
	Range	`0 .. 18446744073709547520`

When this option is set, queries which examine fewer than number rows are not written to the slow query log. The default is 0.

--memlock

Command-Line Format	`--memlock`
Option-File Format	`memlock`
System Variable Name	`locked_in_memory`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

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 newer 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 8.11.4.2, "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

Command-Line Format	`--myisam-block-size=#`
Option-File Format	`myisam-block-size`
	Permitted Values
	Type	`numeric`
	Default	`1024`
	Range	`1024 .. 16384`

The block size to be used for MyISAM index pages.

--myisam-recover-options[=option[,option]...]]

Command-Line Format	`--myisam-recover-options[=name]`
Option-File Format	`myisam-recover-options`
	Permitted Values
	Type	`enumeration`
	Default	`OFF`
	Valid Values	`OFF`
		`DEFAULT`
		`BACKUP`
		`FORCE`
		`QUICK`

Set the MyISAM storage engine recovery mode. The option value is any combination of the values of OFF, DEFAULT, BACKUP, FORCE, or QUICK. If you specify multiple values, separate them by commas. Specifying the option with no argument is the same as specifying DEFAULT, and specifying with an explicit value of "" disables recovery (same as a value of OFF). If recovery is enabled, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or was not closed properly. (The last option works only if you are running with external locking disabled.) If this is the case, mysqld runs a check on the table. If the table was corrupted, mysqld attempts to repair it.

The following options affect how the repair works.

Option	Description
`OFF`	No recovery.
`DEFAULT`	Recovery without backup, forcing, or quick checking.
`BACKUP`	If the data file was changed during recovery, save a backup of the `tbl_name.MYD` file as `tbl_name-datetime.BAK`.
`FORCE`	Run recovery even if we would lose more than one row from the`.MYD` file.
`QUICK`	Do not check the rows in the table if there are not any delete blocks.

Before the server automatically repairs a table, it writes a note about the repair to the error log. If you want to be able to recover from most problems without user intervention, you should use the options BACKUP,FORCE. This forces a repair of a table even if some rows would be deleted, but it keeps the old data file as a backup so that you can later examine what happened.

See Section 14.3.1, "MyISAM Startup Options".

--old-alter-table

Command-Line Format	`--old-alter-table`
Option-File Format	`old-alter-table`
System Variable Name	`old_alter_table`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`OFF`

When this option is given, the server does not use the optimized method of processing an ALTER TABLE operation. It reverts to using a temporary table, copying over the data, and then renaming the temporary table to the original, as used by MySQL 5.0 and earlier. For more information on the operation of ALTER TABLE, see Section 13.1.7, "ALTER TABLE Syntax".

--old-style-user-limits

Command-Line Format	`--old-style-user-limits`
Option-File Format	`old-style-user-limits`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

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 6.3.4, "Setting Account Resource Limits".

--one-thread

Removed	5.6.1
Command-Line Format	`--one-thread`
Option-File Format	`one-thread`

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

--open-files-limit=count

Command-Line Format	`--open-files-limit=#`
Option-File Format	`open-files-limit`
System Variable Name	`open_files_limit`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values (<= 5.6.7)
	Type	`numeric`
	Default	`0`
	Range	`0 .. 65535`
	Permitted Values (>= 5.6.8)
	Type	`numeric`
	Default	`-1 (autosized)`
	Range	`0 .. 65535`

Changes the number of file descriptors available to mysqld. You should try increasing the value of this option if mysqld gives you the error Too many open files. mysqld uses the option value to reserve descriptors with setrlimit(). If the requested number of file descriptors cannot be allocated, mysqld writes a warning to the error log.

mysqld may attempt to allocate more than the requested number of descriptors (if they are available), using the values of max_connections and table_open_cache to estimate whether more descriptors will be needed.

On Unix, the value cannot be set less than ulimit -n.

--partition[=value]

Command-Line Format	`--partition`
Option-File Format	`partition`
Disabled by	`skip-partition`
	Permitted Values
	Type	`boolean`
	Default	`ON`

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

--performance-schema-xxx

Configure a Performance Schema option. For details, see Section 21.11, "Performance Schema Command Options".

--pid-file=path

Command-Line Format	`--pid-file=file_name`
Option-File Format	`pid-file`
System Variable Name	`pid_file`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`

The path name of the process ID file. The server creates the file in the data directory unless an absolute path name is given to specify a different directory. This file is used by other programs such as mysqld_safe to determine the server's process ID.

--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 4.2.3.2, "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.

--plugin-load=plugin_list

Command-Line Format	`--plugin-load=plugin_list`
Option-File Format	`plugin-load`
	Permitted Values
	Type	`string`

This option tells the server to load the named plugins at startup. The option value is a semicolon-separated list of name=plugin_library pairs. Each name is the name of the plugin, and plugin_library is the name of the shared library that contains the plugin code. Each library file must be located 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 load them at startup:

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

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

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.

If a plugin library is named without any preceding plugin name, the server loads all plugins in the library.

Each 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 under configurations when plugins cannot be loaded at runtime.

For additional information about plugin loading, see Section 5.1.8.1, "Installing and Uninstalling Plugins".

--plugin-load-add=plugin_list

Introduced	5.6.3
Command-Line Format	`--plugin-load-add=plugin_list`
Option-File Format	`plugin-load-add`
	Permitted Values
	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. This option was added in MySQL 5.6.3.

--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 5.1.8.1, "Installing and Uninstalling Plugins".

--port=port_num, -P port_num

Command-Line Format	`--port=#`
	`-P`
Option-File Format	`port`
System Variable Name	`port`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`numeric`
	Default	`3306`
	Range	`0 .. 65535`

The port number to use when listening for TCP/IP connections. The port number must be 1024 or higher unless the server is started by the root system user.

--port-open-timeout=num

Command-Line Format	`--port-open-timeout=#`
Option-File Format	`port-open-timeout`
	Permitted Values
	Type	`numeric`
	Default	`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.

--remove [service_name]

Command-Line Format --remove [service_name]

(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 2.3.5.7, "Starting MySQL as a Windows Service".

--safe-mode

Deprecated	5.5.26
Removed	5.6.6
Command-Line Format	`--safe-mode`
Option-File Format	`safe-mode`

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

--safe-user-create

Command-Line Format	`--safe-user-create`
Option-File Format	`safe-user-create`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

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 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.

--secure-auth

Command-Line Format	`--secure-auth`
Option-File Format	`secure-auth`
System Variable Name	`secure_auth`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values (<= 5.6.4)
	Type	`boolean`
	Default	`OFF`
	Permitted Values (>= 5.6.5)
	Type	`boolean`
	Default	`ON`

This option causes the server to block connections by clients that attempt to use accounts that have passwords stored in the old (pre-4.1) format. Use it to prevent all use of passwords employing the old format (and hence insecure communication over the network). Before MySQL 5.6.5, this option is disabled by default. As of MySQL 5.6.5, it is enabled by default; to disable it, use --skip-secure-auth.

Server startup fails with an error if this option is enabled and the privilege tables are in pre-4.1 format. See Section C.5.2.4, "Client does not support authentication protocol".

The mysql client also has a --secure-auth option, which prevents connections to a server if the server requires a password in old format for the client account.

--secure-file-priv=path

Command-Line Format	`--secure-file-priv=path`
Option-File Format	`secure-file-priv`
System Variable Name	`secure_file_priv`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`string`

This option limits the effect of the LOAD_FILE() function and the LOAD DATA and SELECT ... INTO OUTFILE statements to work only with files in the specified directory.

--shared-memory

System Variable Name	`shared_memory`
Variable Scope	Global
Dynamic Variable	No
Platform Specific	windows

Enable shared-memory connections by local clients. This option is available only on Windows.

--shared-memory-base-name=name

System Variable Name	`shared_memory_base_name`
Variable Scope	Global
Dynamic Variable	No
Platform Specific	windows

The name of shared memory to use for shared-memory connections. This option is available only on Windows. The default name is MYSQL. The name is case sensitive.

--skip-concurrent-insert

Turn off the ability to select and insert at the same time on MyISAM tables. (This is to be used only if you think you have found a bug in this feature.) See Section 8.10.3, "Concurrent Inserts".
--skip-external-locking

Do not use external locking (system locking). This affects only MyISAM table access. For more information, including conditions under which it can and cannot be used, see Section 8.10.5, "External Locking".

External locking has been disabled by default since MySQL 4.0.

--skip-event-scheduler

Command-Line Format	`--skip-event-scheduler`
	`--disable-event-scheduler`
Option-File Format	`skip-event-scheduler`

Turns the Event Scheduler OFF. This is not the same as disabling the Event Scheduler, which requires setting --event-scheduler=DISABLED; see The --event-scheduler Option, for more information.

--skip-grant-tables

This option causes the server to start without using the privilege system at all, which gives anyone with access to the server unrestricted access to all databases. You can cause a running server to start using the grant tables again by executing mysqladmin flush-privileges or mysqladmin reload command from a system shell, or by issuing a MySQL FLUSH PRIVILEGES statement after connecting to the server. This option also suppresses loading of plugins that were installed with the INSTALL PLUGIN statement, user-defined functions (UDFs), and scheduled events. To cause plugins to be loaded anyway, use the --plugin-load option.

Note that FLUSH PRIVILEGES might be executed implicitly by other actions performed after startup. For example, mysql_upgrade flushes the privileges during the upgrade procedure.
--skip-host-cache

Disable use of the internal host cache for faster name-to-IP resolution. In this case, the server performs a DNS lookup every time a client connects. See Section 8.11.5.2, "DNS Lookup Optimization and the Host Cache".

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.
--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.
--skip-name-resolve

Do not resolve host names when checking client connections. Use only IP addresses. If you use this option, all Host column values in the grant tables must be IP addresses or localhost. See Section 8.11.5.2, "DNS Lookup Optimization and the Host Cache".
--skip-networking

Do not listen for TCP/IP connections at all. All interaction with mysqld must be made using named pipes or shared memory (on Windows) or Unix socket files (on Unix). This option is highly recommended for systems where only local clients are permitted. See Section 8.11.5.2, "DNS Lookup Optimization and the Host Cache".

--skip-partition

Command-Line Format	`--skip-partition`
	`--disable-partition`
Option-File Format	`skip-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.

--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 Section 6.3.9.4, "SSL Command Options".

--standalone

Command-Line Format	`--standalone`
Option-File 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`
Option-File Format	`super-large-pages`
Platform Specific	solaris
	Permitted Values
	Type (solaris)	`boolean`
	Default	`FALSE`

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`
Option-File Format	`symbolic-links`

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

On Windows, enabling symbolic links enables you to establish a symbolic link to a database directory by creating a db_name.sym file that contains the path to the real directory. See Section 8.11.3.1.3, "Using Symbolic Links for Databases on Windows".
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 options 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 8.11.3.1.2, "Using Symbolic Links for MyISAM Tables on Unix".

--skip-show-database

Command-Line Format	`--skip-show-database`
Option-File Format	`skip-show-database`
System Variable Name	`skip_show_database`
Variable Scope	Global
Dynamic Variable	No

This option sets the skip_show_database system variable that controls who is permitted to use the SHOW DATABASES statement. See Section 5.1.4, "Server System Variables".

--skip-stack-trace

Command-Line Format	`--skip-stack-trace`
Option-File 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 MySQL Internals: Porting to Other Systems.

--skip-thread-priority

Deprecated	5.1.29
Removed	5.6.1
Command-Line Format	`--skip-thread-priority`
Option-File Format	`skip-thread-priority`

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

--slow-query-log[={0|1}]

Command-Line Format	`--slow-query-log`
Option-File Format	`slow-query-log`
System Variable Name	`slow_query_log`
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	`boolean`
	Default	`OFF`

Specify the initial slow query log state. With no argument or an argument of 1, the --slow-query-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

--slow-start-timeout=timeout

Introduced	5.6.5
Command-Line Format	`--slow-start-timeout=#`
Option-File Format	`slow-start-timeout`
	Permitted Values
	Type (windows)	`numeric`
	Default	`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=name`
Option-File Format	`socket`
System Variable Name	`socket`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file name`
	Default	`/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`
Option-File Format	`sql-mode`
System Variable Name	`sql_mode`
Variable Scope	Global, Session
Dynamic Variable	Yes
	Permitted Values (<= 5.6.5)
	Type	`set`
	Default	`''`
	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`
	Permitted Values (>= 5.6.6)
	Type	`set`
	Default	`NO_ENGINE_SUBSTITUTION`
	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. Prior to MySQL 5.6.6, the default was '' (an empty string); beginning with MySQL 5.6.6, the default is NO_ENGINE_SUBSTITUTION. See Section 5.1.7, "Server SQL Modes".

--sysdate-is-now

Command-Line Format	`--sysdate-is-now`
Option-File Format	`sysdate-is-now`
	Permitted Values
	Type	`boolean`
	Default	`FALSE`

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 12.7, "Date and Time Functions" and for SET TIMESTAMP in Section 5.1.4, "Server System Variables".

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

Command-Line Format	`--tc-heuristic-recover=name`
Option-File Format	`tc-heuristic-recover`
	Permitted Values
	Type	`enumeration`
	Valid Values	`COMMIT`
		`RECOVER`

The type of decision to use in the heuristic recovery process. Currently, this option is unused.

--temp-pool

Command-Line Format	`--temp-pool`
Option-File Format	`temp-pool`
	Permitted Values
	Type	`boolean`
	Default	`TRUE`

This option 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. This option is ignored except on Linux.

--transaction-isolation=level

Command-Line Format	`--transaction-isolation=name`
Option-File Format	`transaction-isolation`
	Permitted Values
	Type	`enumeration`
	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 Syntax".

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

Introduced	5.6.5
Command-Line Format	`--transaction-read-only`
Option-File Format	`transaction-read-only`
	Permitted Values
	Type	`boolean`
	Default	`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 Syntax".

This option was added in MySQL 5.6.5.

--tmpdir=path, -t path

Command-Line Format	`--tmpdir=path`
	`-t`
Option-File Format	`tmpdir`
System Variable Name	`tmpdir`
Variable Scope	Global
Dynamic Variable	No
	Permitted Values
	Type	`file 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. If the MySQL server is acting as a replication slave, you should not set --tmpdir to point to a directory on a memory-based file system or to a directory that is cleared when the server host restarts. For more information about the storage location of temporary files, see Section C.5.4.4, "Where MySQL Stores Temporary Files". A replication slave needs some of its temporary files to survive a machine restart so that it can replicate temporary tables or LOAD DATA INFILE operations. If files in the temporary file directory are lost when the server restarts, replication fails.

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

Command-Line Format	`--user=name`
	`-u name`
Option-File Format	`user`
	Permitted Values
	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.

You can assign a value to a server system variable by using 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.

Note that 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.

If you want to restrict the maximum value to which a variable can be set at runtime with SET, you can define this by using the --maximum-var_name=value command-line option.

You can change the values of most system variables for a running server with the SET statement. See Section 13.7.4, "SET Syntax".

Section 5.1.4, "Server System Variables", provides a full description for all variables, and additional information for setting them at server startup and runtime. Section 8.11.2, "Tuning Server Parameters", includes information on optimizing the server by tuning system variables.