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Mysql：命令选项、配置选项、（全局、会话）系统变量、状态变量：命令选项

 

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 4.2.3.2, “Using Option Files”.

MySQL Enterprise.  For expert advice on setting command options, subscribe to the MySQL Enterprise Monitor. For more information, see http://www.mysql.com/products/enterprise/advisors.html.

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:

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

  • --help, -?

    Command Line Format -?
    Config 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
    Config File Format allow-suspicious-udfs
    Value Set
    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 22.3.2.6, “User-Defined Function Security Precautions”.

  • --ansi

    Command Line Format --ansi
    Config 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 1.7.3, “Running MySQL in ANSI Mode”, and Section 5.1.7, “Server SQL Modes”.

  • --basedir=path, -b path

    Command Line Format --basedir=name
    Config File Format basedir
    Option Sets Variable Yes, basedir
    Variable Name basedir
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

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

  • --big-tables

    Command Line Format --big-tables
    Config File Format big-tables
    Option Sets Variable Yes, big_tables
    Variable Name big-tables
    Variable Scope Session
    Dynamic Variable Yes
    Value Set
    Type boolean

    Allow 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=IP

    Command Line Format --bind-address=name
    Config File Format bind-address
    Value Set
    Type string
    Default 0.0.0.0
    Range 0.0.0.0-255.255.255.255

    The IP address to bind to. Only one address can be selected. If this option is specified multiple times, the last address given is used.

    If no address or 0.0.0.0 is specified, the server listens on all interfaces.

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

    Version Introduced 5.1.5
    Command Line Format --binlog-format
    Config File Format binlog-format
    Option Sets Variable Yes, binlog_format
    Variable Name binlog_format
    Variable Scope Both
    Dynamic Variable Yes
    Value Set (>= 5.1.5, <= 5.1.7)
    Type enumeration
    Default STATEMENT
    Valid Values ROW, STATEMENT
    Value Set (>= 5.1.8, <= 5.1.11)
    Type enumeration
    Default STATEMENT
    Valid Values ROW, STATEMENT, MIXED
    Value Set (>= 5.1.12, <= 5.1.28)
    Type enumeration
    Default MIXED
    Valid Values ROW, STATEMENT, MIXED
    Value Set (>= 5.1.29)
    Type enumeration
    Default STATEMENT
    Valid Values ROW, STATEMENT, MIXED

    Specify whether to use row-based, statement-based, or mixed replication (statement-based was the default prior to MySQL 5.1.12; in 5.1.12, the default was changed to mixed replication; in 5.1.29, the default was changed back to statement-based). See Section 16.1.2, “Replication Formats”. This option was added in MySQL 5.1.5.

    Important

    MySQL Cluster.  The default value for this option in all MySQL Cluster NDB 6.1, 6.2, 6.3, and later 6.x releases is MIXED. See Section 17.9.2, “MySQL Cluster Replication — Assumptions and General Requirements”, for more information.

  • --bootstrap

    Command Line Format --bootstrap
    Config 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.

    This option is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.10.2, “Typical configure Options”.

  • --character-sets-dir=path

    Command Line Format --character-sets-dir=name
    Config File Format character-sets-dir
    Option Sets Variable Yes, character_sets_dir
    Variable Name character-sets-dir
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

    The directory where character sets are installed. See Section 9.2, “The Character Set Used for Data and Sorting”.

  • --character-set-client-handshake

    Command Line Format --character-set-client-handshake
    Config File Format character-set-client-handshake
    Value Set
    Type boolean
    Default TRUE

    Don't 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

    Version Introduced 5.1.6
    Command Line Format --character-set-filesystem=name
    Config File Format character-set-filesystem
    Option Sets Variable Yes, character_set_filesystem
    Variable Name character_set_filesystem
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type string

    The file system character set. This option sets the character_set_filesystem system variable. It was added in MySQL 5.1.6.

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

    Command Line Format --character-set-server
    Config File Format character-set-server
    Option Sets Variable Yes, character_set_server
    Variable Name character_set_server
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type string

    Use charset_name as the default server character set. See Section 9.2, “The Character Set Used for Data and Sorting”. If you use this option to specify a non-default character set, you should also use --collation-server to specify the collation.

  • --chroot=path, -r path

    Command Line Format --chroot=name
    Config File Format chroot
    Value Set
    Type filename

    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
    Config File Format collation-server
    Option Sets Variable Yes, collation_server
    Variable Name collation_server
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type string

    Use collation_name as the default server collation. See Section 9.2, “The Character Set Used for Data and Sorting”.

  • --console

    Command Line Format --console
    Config File Format console
    Platform Specific windows

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

  • --core-file

    Command Line Format --core-file
    Config File Format core-file
    Value Set
    Type boolean
    Default TRUE

    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=name
    Config File Format datadir
    Option Sets Variable Yes, datadir
    Variable Name datadir
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

    The path to the data directory.

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

    Command Line Format --debug[=debug_options]
    Config File Format debug
    Variable Name debug
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type string
    Default 'd:t:o,/tmp/mysqld.trace

    If MySQL is configured with --with-debug, 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.

    As of MySQL 5.1.12, using --with-debug 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.

  • --default-character-set=charset_name (DEPRECATED)

    Command Line Format --default-character-set=name
    Config File Format default-character-set
    Deprecated 5.0
    Value Set
    Type string

    Use charset_name as the default character set. This option is deprecated in favor of --character-set-server. See Section 9.2, “The Character Set Used for Data and Sorting”.

  • --default-collation=collation_name

    Command Line Format --default-collation=name
    Variable Name default-collation
    Variable Scope  
    Dynamic Variable No
    Deprecated 4.1.3
    Value Set
    Type string

    Use collation_name as the default collation. This option is deprecated in favor of --collation-server. See Section 9.2, “The Character Set Used for Data and Sorting”.

  • --default-storage-engine=type

    Command Line Format --default-storage-engine=name
    Config File Format default-storage-engine

    Set the default storage engine (table type) for tables. See Chapter 13, Storage Engines.

  • --default-table-type=type

    Command Line Format --default-table-type=name
    Config File Format default-table-type
    Deprecated 5.0, by default-storage-engine
    Value Set
    Type string

    This option is a deprecated synonym for --default-storage-engine.

  • --default-time-zone=timezone

    Command Line Format --default-time-zone=name
    Config File Format default-time-zone
    Value Set
    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]
    Config File Format delay-key-write
    Option Sets Variable Yes, delay_key_write
    Variable Name delay-key-write
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    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 7.5.3, “Tuning Server Parameters”, and Section 13.5.1, “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=name
    Config 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 --named_pipe
    Config File Format enable-named-pipe
    Platform Specific windows

    Enable support for named pipes. This option applies only on Windows NT, 2000, XP, and 2003 systems. For MySQL 5.1.20 and earlier, this option is available only when using the mysqld-nt and mysqld-debug servers that support named-pipe connections. For MySQL 5.1.21 and later, mysqld-nt is not available, but support is included in the standard mysqld and mysqld-debug servers.

  • --enable-pstack

    Command Line Format --enable-pstack
    Config File Format enable-pstack
    Value Set
    Type boolean
    Default FALSE

    Print a symbolic stack trace on failure.

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

    Command Line Format --engine-condition-pushdown
    Config File Format engine-condition-pushdown
    Option Sets Variable Yes, engine_condition_pushdown
    Variable Name engine_condition_pushdown
    Variable Scope Both
    Dynamic Variable Yes
    Value Set (>= 5.1.0)
    Type boolean
    Default ON

    Sets the engine_condition_pushdown system variable. For more information, see Section 7.2.7, “Condition Pushdown Optimization”.

  • --event-scheduler[=value]

    Version Introduced 5.1.6
    Command Line Format --event-scheduler[=value]
    Config File Format event-scheduler
    Option Sets Variable Yes, event_scheduler
    Variable Name event_scheduler
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    Type enumeration
    Default OFF
    Valid Values ON, OFF, DISABLED

    Enable or disable, and start or stop, the event scheduler. This option was added in MySQL 5.1.6. Note that its permitted values and behaviour changed in MySQL 5.1.11, and again in MySQL 5.1.12.

    For detailed information, see The event-scheduler Option.

  • --exit-info[=flags], -T [flags]

    Command Line Format --exit-info[=flags]
    Config File Format exit-info
    Value Set
    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
    Config File Format external-locking
    Option Sets Variable Yes, skip_external_locking
    Disabled by skip-external-locking
    Value Set
    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. This option previously was named --enable-locking.

    For more information about external locking, including conditions under which it can and cannot be used, see Section 7.3.4, “External Locking”.

  • --flush

    Command Line Format --flush
    Config File Format flush
    Variable Name flush
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    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 B.1.4.2, “What to Do If MySQL Keeps Crashing”.

  • --gdb

    Command Line Format --gdb
    Config File Format gdb
    Value Set
    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.

  • --general-log[={0|1}]

    Version Introduced 5.1.12
    Command Line Format --general-log
    Config File Format general-log
    Option Sets Variable Yes, general_log
    Variable Name general_log
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    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. This option was added in MySQL 5.1.12.

  • --init-file=file_name

    Command Line Format --init-file=name
    Config File Format init-file
    Option Sets Variable Yes, init_file
    Variable Name init_file
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

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

    This option is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.10.2, “Typical configure Options”.

  • --innodb-xxx

    The InnoDB options are listed in Section 13.6.3, “InnoDB Startup Options and System Variables”.

  • --language=lang_name, -L lang_name

    Command Line Format --language=name
    Config File Format language
    Option Sets Variable Yes, language
    Variable Name language
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename
    Default /usr/local/mysql/share/mysql/english/

    Return client error messages in the given language. 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 9.3, “Setting the Error Message Language”.

  • --large-pages

    Command Line Format --large-pages
    Config File Format large-pages
    Option Sets Variable Yes, large_pages
    Variable Name large_pages
    Variable Scope Global
    Dynamic Variable No
    Platform Specific linux
    Value Set
    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.

    Currently, MySQL supports only the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 7.5.9, “Enabling Large Page Support”.

    --large-pages is disabled by default.

  • --log[=file_name], -l [file_name]

    Version Deprecated 5.1.29
    Command Line Format --log[=name]
    Config File Format log
    Option Sets Variable Yes, log
    Variable Name log
    Variable Scope Global
    Dynamic Variable Yes
    Deprecated 5.1.29, by general-log
    Value Set
    Type string
    Default OFF

    This option enables logging to the general query log, which contains entries that record client connections and SQL statements received from clients. The log output destination can be selected with the --log-output option as of MySQL 5.1.6. Before 5.1.6, logging occurs to the general query log file. If you omit the file name, MySQL uses host_name.log as the file name. See Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”, and Section 5.2.3, “The General Query Log”.

    As of MySQL 5.1.29, the --log option is deprecated and will be removed (along with the log system variable) in MySQL 7.0. 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]
    Config File Format log-error
    Option Sets Variable Yes, log_error
    Variable Name log_error
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

    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]
    Config File Format log-isam
    Value Set
    Type filename

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

  • --log-long-format (DEPRECATED)

    Command Line Format --log-long-format
    Config File Format log-long-format
    Deprecated 4.1

    Log extra information to the binary log and slow query log, if they have been activated. For example, the user name and timestamp are logged for all queries. This option is deprecated, as it now represents the default logging behavior. (See the description for --log-short-format.) The --log-queries-not-using-indexes option is available for the purpose of logging queries that do not use indexes to the slow query log.

  • --log-output[=value,...]

    Version Introduced 5.1.6
    Command Line Format --log-output[=name]
    Config File Format log-output
    Option Sets Variable Yes, log_output
    Variable Name log_output
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    Type enumeration
    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. If the option is given without a value, the default is FILE. (For MySQL 5.1.6 through 5.1.20, the default is TABLE.) 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. (Before MySQL 5.1.29, enable the logs with the --log and --log-slow-queries options. The options take an optional file name argument to specify the log file name.) For more information, see Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”.

    The --log-output option was added in MySQL 5.1.6.

  • --log-queries-not-using-indexes

    Version Deprecated 5.1.29
    Command Line Format --log-queries-not-using-indexes
    Config File Format log-queries-not-using-indexes
    Option Sets Variable Yes, log_queries_not_using_indexes
    Variable Name log_queries_not_using_indexes
    Variable Scope Global
    Dynamic Variable Yes
    Deprecated 5.1.29, by slow-query-log
    Value Set
    Type boolean

    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-short-format

    Command Line Format --log-short-format
    Config File Format log-short-format
    Value Set
    Type boolean
    Default FALSE

    Originally intended to log less information to the binary log and slow query log, if they have been activated. However, this option is not operational.

  • --log-slow-admin-statements

    Command Line Format --log-slow-admin-statements
    Config File Format log-slow-admin-statements
    Value Set
    Type boolean
    Default FALSE

    Log slow administrative statements such as OPTIMIZE TABLE, ANALYZE TABLE, and ALTER TABLE to the slow query log.

  • --log-slow-queries[=file_name]

    Command Line Format --log-slow-queries[=name]
    Config File Format log-slow-queries
    Option Sets Variable Yes, log_slow_queries
    Variable Name log_slow_queries
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    Type boolean

    This option enables logging to the slow query log, which contains entries for all queries that have taken more than long_query_time seconds to execute. See the descriptions of the --log-long-format and --log-short-format options for details.

    The log output destination can be selected with the --log-output option as of MySQL 5.1.6. Before 5.1.6, logging occurs to the slow query log file. If you omit the file name, MySQL uses host_name-slow.log as the file name. See Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”, and Section 5.2.5, “The Slow Query Log”.

    As of MySQL 5.1.29, the --log-slow-queries option is deprecated and will be removed (along with the log_slow_queries system variable) in MySQL 7.0. 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
    Config File Format log-tc
    Value Set
    Type filename
    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=#
    Config File Format log-tc-size
    Value Set
    Platform Bit Size 32
    Type numeric
    Default 24576
    Max Value 4294967295
    Value Set
    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[=#]
    Config File Format log-warnings
    Option Sets Variable Yes, log_warnings
    Variable Name log_warnings
    Variable Scope Both
    Dynamic Variable Yes
    Disabled by skip-log-warnings
    Value Set
    Platform Bit Size 32
    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. See Section B.1.2.11, “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.

  • --low-priority-updates

    Command Line Format --low-priority-updates
    Config File Format low-priority-updates
    Option Sets Variable Yes, low_priority_updates
    Variable Name low_priority_updates
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type boolean
    Default FALSE

    Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower priority than selects. This can also be done via {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 7.3.2, “Table Locking Issues”.

  • --min-examined-row-limit=number

    Version Introduced 5.1.21
    Command Line Format --min-examined-row-limit=#
    Config File Format min-examined-row-limit
    Variable Name min_examined_row_limit
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Platform Bit Size 32
    Type numeric
    Default 0
    Range 0-4294967295
    Value Set
    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.

    This option was introduced in MySQL 5.1.21.

  • --memlock

    Command Line Format --memlock
    Config File Format memlock
    Variable Name locked_in_memory
    Variable Scope Global
    Dynamic Variable No
    Value Set
    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 as well as most Linux distributions that use a 2.4 or newer kernel. 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

    Using this option requires that you run the server as root, which, for reasons of security, is normally not a good idea. See Section 5.3.5, “How to Run MySQL as a Normal User”.

    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=#
    Config File Format myisam-block-size
    Value Set
    Type numeric
    Default 1024
    Range 1024-16384

    The block size to be used for MyISAM index pages.

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

    Command Line Format --myisam-recover[=name]
    Config File Format myisam-recover
    Value Set
    Type enumeration
    Default OFF
    Valid Values DEFAULT, BACKUP, FORCE, QUICK

    Set the MyISAM storage engine recovery mode. The option value is any combination of the values of 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 not giving the option). If recovery is enabled, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or wasn't 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
    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 Don't check the rows in the table if there aren't 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 13.5.1, “MyISAM Startup Options”.

  • --old-passwords

    Command Line Format --old_passwords
    Config File Format old-passwords
    Option Sets Variable Yes, old_passwords
    Variable Name old_passwords
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    Type boolean
    Default FALSE

    Force the server to generate short (pre-4.1) password hashes for new passwords. This is useful for compatibility when the server must support older client programs. See Section 5.5.6.3, “Password Hashing in MySQL”.

  • --old-style-user-limits

    Command Line Format --old-style-user-limits
    Config File Format old-style-user-limits
    Value Set
    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 5.5.4, “Limiting Account Resources”.

  • --one-thread

    Command Line Format --one-thread
    Config File Format one-thread

    Only use one thread (for debugging under Linux). This option is available only if the server is built with debugging enabled. See MySQL Internals: Porting.

    As of MySQL 5.1.17, this option is deprecated; use --thread_handling=one-thread instead.

  • --open-files-limit=count

    Command Line Format --open-files-limit=#
    Config File Format open-files-limit
    Option Sets Variable Yes, open_files_limit
    Variable Name open_files_limit
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type numeric
    Default 0
    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.

  • --pid-file=path

    Command Line Format --pid-file=name
    Config File Format pid-file
    Option Sets Variable Yes, pid_file
    Variable Name pid_file
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

    The path name of the process ID file. This file is used by other programs such as mysqld_safe to determine the server's process ID.

  • --plugin-load=plugin_list

    Version Introduced 5.1.18
    Command Line Format --plugin-load=plugin_list
    Config File Format plugin-load
    Value Set
    Type string

    Under normal startup, the server determines which plugins to load by reading the mysql.plugins system table. This option enables plugins to be loaded even when --skip-grant-tables is given (which tells the server not to read system tables). This option also enables plugins to be loaded at startup under configurations when plugins cannot be loaded at runtime. The option was added in MySQL 5.1.18.

    The option value is a colon-separated list of name=plugin_library values. 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

    All plugins to load must be named in the same --plugin-load option. If multiple --plugin-load options are given, only the last one is used.

    The plugins are loaded for a single invocation of mysqld only. After a restart, the plugins are 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.

  • --port=port_num, -P port_num

    Command Line Format --port=#
    Config File Format port
    Option Sets Variable Yes, port
    Variable Name port
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type numeric
    Default 3306

    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

    Version Introduced 5.1.5
    Command Line Format --port-open-timeout=#
    Config File Format port-open-timeout
    Value Set
    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. This option was added in MySQL 5.1.5.

  • --safe-mode

    Command Line Format --safe-mode
    Config File Format safe-mode
    Deprecated 5.0

    Skip some optimization stages.

  • --safe-show-database (DEPRECATED)

    Command Line Format --safe-show-database
    Config File Format safe-show-database
    Variable Name safe_show_database
    Variable Scope Global
    Dynamic Variable Yes
    Deprecated 4.0.2
    Value Set
    Type boolean

    See Section 5.4.1, “Privileges Provided by MySQL”.

  • --safe-user-create

    Command Line Format --safe-user-create
    Config File Format safe-user-create
    Value Set
    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: 

    		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
    Config File Format secure-auth
    Option Sets Variable Yes, secure_auth
    Variable Name secure_auth
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    Type boolean
    Default FALSE

    Disallow authentication by clients that attempt to use accounts that have old (pre-4.1) passwords.

  • --secure-file-priv=path

    Version Introduced 5.1.17
    Command Line Format --secure-file-priv
    Config File Format secure-file-priv
    Option Sets Variable Yes, secure_file_priv
    Variable Name secure_file_priv
    Variable Scope Global
    Dynamic Variable No
    Value Set
    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.

    This option was added in MySQL 5.1.17.

  • --shared-memory

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

  • --shared-memory-base-name=name

    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 7.3.3, “Concurrent Inserts”.

  • --skip-external-locking

    Do not use external locking (system locking). For more information about external locking, including conditions under which it can and cannot be used, see Section 7.3.4, “External Locking”.

    External locking has been disabled by default since MySQL 4.0.

  • --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, user-defined functions (UDFs), and, beginning with MySQL 5.1.17, scheduled events. To cause plugins to be loaded anyway, use the --plugin-load option.

    --skip-grant-tables is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.10.2, “Typical configure Options”.

  • --skip-host-cache

    Do not use the internal host name cache for faster name-to-IP resolution. Instead, query the DNS server every time a client connects. See Section 7.5.11, “How MySQL Uses DNS”.

  • --skip-innodb

    Disable the InnoDB storage engine. This saves memory and disk space and might speed up some operations. Do not use this option if you require InnoDB tables.

  • --skip-name-resolve

    Do not resolve host names when checking client connections. Use only IP numbers. If you use this option, all Host column values in the grant tables must be IP numbers or localhost. See Section 7.5.11, “How MySQL Uses DNS”.

  • --skip-networking

    Don't listen for TCP/IP connections at all. All interaction with mysqld must be made via 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 allowed. See Section 7.5.11, “How MySQL Uses DNS”.

  • --ssl*

    Options that begin with --ssl specify whether to allow clients to connect via SSL and indicate where to find SSL keys and certificates. See Section 5.5.7.3, “SSL Command Options”.

  • --standalone

    Command Line Format --standalone
    Config File Format standalone
    Platform Specific windows

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

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

    Command Line Format --symbolic-links
    Config File Format symbolic-links

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

  • --skip-safemalloc

    Command Line Format --skip-safe-malloc
    Config File Format skip-safemalloc

    If MySQL is configured with --with-debug=full, all MySQL programs check for memory overruns during each memory allocation and memory freeing operation. This checking is very slow, so for the server you can avoid it when you don't need it by using the --skip-safemalloc option.

  • --skip-show-database

    Command Line Format --skip-show-database
    Config File Format skip-show-database
    Option Sets Variable Yes, skip_show_database
    Variable Name skip_show_database
    Variable Scope Global
    Dynamic Variable No

    With this option, the SHOW DATABASES statement is allowed only to users who have the SHOW DATABASES privilege, and the statement displays all database names. Without this option, SHOW DATABASES is allowed to all users, but displays each database name only if the user has the SHOW DATABASES privilege or some privilege for the database. Note that any global privilege is considered a privilege for the database.

  • --skip-stack-trace

    Command Line Format --skip-stack-trace
    Config File Format skip-stack-trace

    Don't 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.

  • --skip-thread-priority

    Version Deprecated 5.1.29
    Command Line Format --skip-thread-priority
    Config File Format skip-thread-priority
    Deprecated 5.1.29

    Disable using thread priorities for faster response time. This option is deprecated as of MySQL 5.1.29 and is removed in MySQL 6.0.

  • --slow-query-log[={0|1}]

    Version Introduced 5.1.12
    Command Line Format
    --slow-query-log 5.1.29
    Config File Format
    slow-query-log 5.1.29
    Option Sets Variable Yes, slow_query_log
    Variable Name slow_query_log
    Variable Scope Global
    Dynamic Variable Yes
    Value Set
    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. This option was added in MySQL 5.1.12.

  • --socket=path

    Command Line Format --socket=name
    Config File Format socket
    Option Sets Variable Yes, socket
    Variable Name socket
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename
    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. 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
    Config File Format sql-mode
    Option Sets Variable Yes, sql_mode
    Variable Name sql_mode
    Variable Scope Both
    Dynamic Variable Yes
    Value Set
    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

    Set the SQL mode. See Section 5.1.7, “Server SQL Modes”.

  • --sysdate-is-now

    Version Introduced 5.1.8
    Command Line Format --sysdate-is-now
    Config File Format sysdate-is-now
    Value Set
    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 11.6, “Date and Time Functions” and for SET TIMESTAMP in Section 5.1.4, “Session System Variables”.

    This option was added in MySQL 5.1.8.

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

    Command Line Format --tc-heuristic-recover=name
    Config File Format tc-heuristic-recover
    Value Set
    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
    Config File Format temp-pool
    Value Set
    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. As of MySQL 5.1.31, this option is ignored except on Linux.

  • --transaction-isolation=level

    Command Line Format --transaction-isolation=name
    Config File Format transaction-isolation
    Value Set
    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 12.4.6, “SET TRANSACTION Syntax”.

  • --tmpdir=path, -t path

    Command Line Format --tmpdir=name
    Config File Format tmpdir
    Option Sets Variable Yes, tmpdir
    Variable Name tmpdir
    Variable Scope Global
    Dynamic Variable No
    Value Set
    Type filename

    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, NetWare, and OS/2. 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 B.1.4.4, “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
    Config File Format user
    Value Set
    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 5.3.1, “General 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 allowable value if only certain values are allowed.

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 12.5.4, “SET Syntax”.

Section 5.1.3, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. Section 7.5.3, “Tuning Server Parameters”, includes information on optimizing the server by tuning system variables

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