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 4.2.6, “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 6.3.6.5, “SSL Command Options”.

• Binary log control options: See Section 16.1.2.4, “Binary Log Options and Variables”.

• Replication-related options: See Section 16.1.2, “Replication and Binary Logging Options and Variables”.

• Options specific to particular storage engines: See Section 14.1.1, “MyISAM Startup Options”, Section 14.5.3, “BDB Startup Options”, Section 14.2.2, “InnoDB Startup Options and System Variables”, and Section 17.3.3.7.1, “mysqld Command Options for MySQL Cluster”.

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

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

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

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

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

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.

It is also possible to set variables by using --set-variable=var_name=value or -O var_name=value syntax. This syntax is deprecated.

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 8.12.2, “Tuning Server Parameters”, includes information on optimizing the server by tuning system variables.

• --help, -?

  Command-Line Format

  --help

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

• --allow-suspicious-udfs

  Introduced	5.0.3
  Command-Line 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. This option was added in version 5.0.3. See Section 21.2.2.6, “UDF Security Precautions”.

• --ansi

  Command-Line Format

  --ansi

  Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise control over the server SQL mode, use the --sql-mode option instead. See Section 1.8, “MySQL Standards Compliance”, and Section 5.1.7, “Server SQL Modes”.

• --basedir=dir_name, -b dir_name

  Command-Line Format	--basedir=dir_name
  System Variable	Name	basedir
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	directory name

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

• --big-tables

  Command-Line Format	--big-tables
  System Variable	Name	big_tables
  	Variable Scope	Session
  	Dynamic Variable	Yes
  Permitted Values	Type	boolean
  	Default	OFF

  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
  Permitted Values	Type	string
  	Default	0.0.0.0

  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. The default address is 0.0.0.0. To specify an address explicitly, use the --bind-address=addr option at server startup, where addr is an IPv4 address or a host name. If addr is a host name, the server resolves the name to an IPv4 address and binds to that address.

  The server treats different types of addresses as follows:

  • If the address is 0.0.0.0, the server accepts TCP/IP connections on all server host IPv4 interfaces.

  • If the address is a “regular” IPv4 address (such as 127.0.0.1), the server accepts TCP/IP connections only for that particular IPv4 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 connect to that address. Otherwise, you will not be able to shut down the server. For example, if you bind to 0.0.0.0, you can connect to the server using all existing accounts. But if you bind to 127.0.0.1, the server accepts connections only on that address. In this case, first make sure that the 'root'@'127.0.0.1' account is present in the mysql.user table so that you can still connect to the server to shut it down.

• --bootstrap

  Command-Line Format

  --bootstrap

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

  This option is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.17.3, “MySQL Source-Configuration Options”.

• --character-sets-dir=dir_name

  Command-Line Format	--character-sets-dir=dir_name
  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
  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

  Introduced	5.0.19
  Command-Line Format	--character-set-filesystem=name
  System Variable	Name	character_set_filesystem
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values	Type	string
  	Default	binary

  The file system character set. This option sets the character_set_filesystem system variable. It was added in MySQL 5.0.19.

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

  Command-Line Format	--character-set-server
  System Variable	Name	character_set_server
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values	Type	string
  	Default	latin1

  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=dir_name, -r dir_name

  Command-Line Format	--chroot=dir_name
  Permitted Values	Type	directory name

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

• --collation-server=collation_name

  Command-Line Format	--collation-server
  System Variable	Name	collation_server
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values	Type	string
  	Default	latin1_swedish_ci

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

• --console

  Command-Line 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, whichever option is given last takes precedence.

• --core-file

  Command-Line 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 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=dir_name, -h dir_name

  Command-Line Format	--datadir=dir_name
  System Variable	Name	datadir
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	directory name

  The path to the data directory.

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

  Command-Line Format	--debug[=debug_options]
  System Variable	Name	debug
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values (Unix)	Type	string
  	Default	d:t:i:o,/tmp/mysqld.trace
  Permitted Values (Windows)	Type	string
  	Default	d:t:i:O,\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,/tmp/mysqld.trace on Unix and d:t:i:O,\mysqld.trace on Windows.

  As of MySQL 5.0.25, 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.

  For more information, see Section 21.3.3, “The DBUG Package”.

• --default-character-set=charset_name

  Deprecated	5.0.0
  Command-Line Format	--default-character-set=name
  Permitted Values	Type	string

  Use charset_name as the default character set. This option is deprecated in favor of --character-set-server. See Section 10.5, “Character Set Configuration”. --default-character-set is removed in MySQL 5.5.

• --default-collation=collation_name

  Deprecated	4.1.3
  Command-Line Format	--default-collation=name
  Permitted Values	Type	string

  Use collation_name as the default collation. This option is deprecated in favor of --collation-server. See Section 10.5, “Character Set Configuration”. --default-collation is removed in MySQL 5.5.

• --default-storage-engine=type

  Command-Line Format	--default-storage-engine=name
  System Variable	Name	storage_engine
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values	Type	enumeration
  	Default	MyISAM

  Set the default storage engine (table type) for tables. See Chapter 14, Storage Engines.

• --default-table-type=type

  Deprecated	5.0.0, by default-storage-engine
  Command-Line Format	--default-table-type=name
  Permitted Values	Type	string

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

• --default-time-zone=timezone

  Command-Line Format	--default-time-zone=name
  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.

• --defaults-extra-file=file_name

  Read this option file after the global option file but (on Unix) before the user option file. As of MySQL 5.0.6, if the file does not exist or is otherwise inaccessible, an error occurs. file_name is the full path name to the file.

• --defaults-file=file_name

  Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. file_name is the full path name to the file.

• --defaults-group-suffix=str

  Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqld normally reads the [mysqld] group. If the --defaults-group-suffix=_other option is given, mysqld also reads the [mysqld_other] group. This option was added in MySQL 5.0.10.

• --delay-key-write[={OFF|ON|ALL}]

  Command-Line Format	--delay-key-write[=name]
  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 8.12.2, “Tuning Server Parameters”, and Section 14.1.1, “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

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

• --enable-locking

  This option is deprecated. Use --external-locking instead.

• --enable-named-pipe

  Command-Line Format	--enable-named-pipe
  Platform Specific	Windows

  Enable support for named pipes. This option can be used only with the mysqld-nt and mysqld-debug servers that support named-pipe connections.

• --enable-pstack

  Command-Line Format	--enable-pstack
  Permitted Values	Type	boolean
  	Default	FALSE

  Print a symbolic stack trace on failure. This capability is available only on Intel Linux systems, and only if MySQL was configured with the --with-pstack option.

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

  Introduced	5.0.3
  Command-Line Format	--engine-condition-pushdown
  System Variable	Name	engine_condition_pushdown
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values (>= 5.0.3)	Type	boolean
  	Default	OFF

  Sets the engine_condition_pushdown system variable. For more information, see Section 8.2.1.5, “Engine Condition Pushdown Optimization”.

  This variable was added in MySQL 5.0.3.

• --exit-info[=flags], -T [flags]

  Command-Line Format	--exit-info[=flags]
  Permitted Values	Type	integer

  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
  Permitted Values	Type	boolean
  	Default	FALSE

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

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

  External locking affects only MyISAM table access. For more information, including conditions under which it can and cannot be used, see Section 8.11.4, “External Locking”.

• --flush

  Command-Line 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 B.5.3.3, “What to Do If MySQL Keeps Crashing”.

• --gdb

  Command-Line 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 Section 21.3, “Debugging and Porting MySQL”.

• --init-file=file_name

  Command-Line Format	--init-file=file_name
  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.

  This option is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.17.3, “MySQL Source-Configuration Options”.

• --innodb-safe-binlog

  Deprecated	5.0.3
  Removed	5.0.3
  Command-Line Format	--innodb-safe-binlog
  Permitted Values	Type	boolean

  If this option is given, then after a crash recovery by InnoDB, mysqld truncates the binary log after the last not-rolled-back transaction in the log. The option also causes InnoDB to print an error if the binary log is smaller or shorter than it should be. See Section 5.2.3, “The Binary Log”. This option was removed in MySQL 5.0.3, having been made obsolete by the introduction of XA transaction support.

• --innodb-xxx

  Set an option for the InnoDB storage engine. The InnoDB options are listed in Section 14.2.2, “InnoDB Startup Options and System Variables”.

• --install [service_name]

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

  (Windows only) Install the server as a Windows service that starts automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.

  Note

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

• --install-manual [service_name]

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

  (Windows only) Install the server as a Windows service that must be started manually. It does not start automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.

  Note

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

• --language=lang_name, -L lang_name

  Command-Line Format	--language=name
  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”.

• --large-pages

  Introduced	5.0.3
  Command-Line Format	--large-pages
  System Variable	Name	large_pages
  	Variable Scope	Global
  	Dynamic Variable	No
  Platform Specific	Linux
  Permitted Values (Linux)	Type	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 supports only the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.12.5.2, “Enabling Large Page Support”.

  --large-pages is disabled by default. It was added in MySQL 5.0.3.

• --local-service

  Command-Line Format

  --local-service

  (Windows only) A --local-service option following the service name causes the server to run using the LocalService Windows account that has limited system privileges. This account is available only for Windows XP or newer. If both --defaults-file and --local-service are given following the service name, they can be in any order. See Section 2.10.4.7, “Starting MySQL as a Windows Service”.

• --log[=file_name], -l [file_name]

  Command-Line Format	--log[=file_name]
  System Variable	Name	log
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	file name

  Log connections and SQL statements received from clients to this file. See Section 5.2.2, “The General Query Log”. If you omit the file name, MySQL uses host_name.log as the file name.

• --log-error[=file_name]

  Command-Line Format	--log-error[=file_name]
  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 5.2.1, “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[=file_name]
  Permitted Values	Type	file name

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

• --log-long-format

  Deprecated	4.1.0
  Command-Line Format	--log-long-format

  Log extra information to the update log, binary update 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-long-format is removed in MySQL 5.5.

• --log-queries-not-using-indexes

  Command-Line Format	--log-queries-not-using-indexes
  System Variable (>= 5.0.23)	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 5.2.4, “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
  Permitted Values	Type	boolean
  	Default	FALSE

  Originally intended to log less information to the update 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
  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.

• --log-slow-queries[=file_name]

  Command-Line Format	--log-slow-queries[=name]
  System Variable	Name	log_slow_queries
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	boolean

  Log all queries that have taken more than long_query_time seconds to execute to this file. See Section 5.2.4, “The Slow Query Log”. See the descriptions of the --log-long-format and --log-short-format options for details.

• --log-tc=file_name

  Introduced	5.0.3
  Command-Line Format	--log-tc=file_name
  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. This option is unused. Added in MySQL 5.0.3.

• --log-tc-size=size

  Introduced	5.0.3
  Command-Line Format	--log-tc-size=#
  Permitted Values (32-bit platforms)	Type	integer
  	Default	24576
  	Max Value	4294967295
  Permitted Values (64-bit platforms)	Type	integer
  	Default	24576
  	Max Value	18446744073709547520

  The size in bytes of the memory-mapped transaction coordinator log. The default size is 24KB. Added in MySQL 5.0.3.

• --log-warnings[=level], -W [level]

  Command-Line Format	--log-warnings[=#]
  System Variable	Name	log_warnings
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values (32-bit platforms)	Type	integer
  	Default	1
  	Min Value	0
  	Max Value	4294967295
  Permitted Values (64-bit platforms)	Type	integer
  	Default	1
  	Min Value	0
  	Max Value	18446744073709547520

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

• --low-priority-updates

  Command-Line 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 8.11.2, “Table Locking Issues”.

• --memlock

  Command-Line Format	--memlock
  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 8.12.5.2, “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=#
  Permitted Values	Type	integer
  	Default	1024
  	Min Value	1024
  	Max Value	16384

  The block size to be used for MyISAM index pages.

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

  Command-Line Format	--myisam-recover[=name]
  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 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 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
  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 14.1.1, “MyISAM Startup Options”.

• --no-defaults

  Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read.

• --old-style-user-limits

  Introduced	5.0.3
  Command-Line 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”. This option was added in MySQL 5.0.3.

• --one-thread

  Command-Line 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 Section 21.3, “Debugging and Porting MySQL”.

• --open-files-limit=count

  Command-Line Format	--open-files-limit=#
  System Variable	Name	open_files_limit
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	integer
  	Default	0
  	Min Value	0
  	Max Value	platform dependent

  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(). Internally, the maximum value for this option is the maximum unsigned integer value, but the actual maximum is platform dependent. 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_cache to estimate whether more descriptors will be needed.

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

• --pid-file=file_name

  Command-Line Format	--pid-file=file_name
  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.

• --port=port_num, -P port_num

  Command-Line Format	--port=#
  System Variable	Name	port
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	integer
  	Default	3306
  	Min Value	0
  	Max Value	65535

  The port number to use when listening for TCP/IP connections. On Unix and Unix-like systems, the port number must be 1024 or higher unless the server is started by the root system user.

• --port-open-timeout=num

  Introduced	5.0.19
  Command-Line Format	--port-open-timeout=#
  Permitted Values	Type	integer
  	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 5.0.19.

• --print-defaults

  Print the program name and all options that it gets from option files.

• --remove [service_name]

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

  (Windows only) Remove a MySQL Windows service. The default service name is MySQL if no service_name value is given. For more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.

• --safe-mode

  Command-Line Format

  --safe-mode

  Skip some optimization stages. This option is deprecated and is removed in MySQL 5.6.

• --safe-show-database

  Deprecated	4.0.2
  Command-Line Format	--safe-show-database
  Permitted Values	Type	boolean

  This option is deprecated and does not do anything because there is a SHOW DATABASES privilege that can be used to control access to database names on a per-account basis. See Section 6.2.1, “Privileges Provided by MySQL”. --safe-show-database is removed in MySQL 5.5.

• --safe-user-create

  Command-Line 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
  System Variable	Name	secure_auth
  	Variable Scope	Global
  	Dynamic Variable	Yes
  Permitted Values	Type	boolean
  	Default	OFF

  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).

  Server startup fails with an error if this option is enabled and the privilege tables are in pre-4.1 format. See Section B.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=dir_name

  Introduced	5.0.38
  Command-Line Format	--secure-file-priv=dir_name
  System Variable	Name	secure_file_priv
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	string
  	Default	empty
  	Valid Values	empty
  		dirname

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

  This option was added in MySQL 5.0.38.

• --shared-memory

  Command-Line Format	--shared_memory[={0,1}]
  System Variable	Name	shared_memory
  	Variable Scope	Global
  	Dynamic Variable	No
  Platform Specific	Windows
  Permitted Values	Type	boolean
  	Default	FALSE

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

• --shared-memory-base-name=name

  Command-Line Format	--shared_memory_base_name=name
  System Variable	Name	shared_memory_base_name
  	Variable Scope	Global
  	Dynamic Variable	No
  Platform Specific	Windows
  Permitted Values	Type	string
  	Default	MYSQL

  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-bdb

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

• --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 8.11.3, “Concurrent Inserts”.

• --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 user-defined functions (UDFs).

  FLUSH PRIVILEGES might be executed implicitly by other actions performed after startup. For example, mysql_upgrade flushes the privileges during the upgrade procedure.

  This option is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.17.3, “MySQL Source-Configuration Options”.

• --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 8.12.6.2, “DNS Lookup Optimization and the Host Cache”.

• --skip-innodb

  Disable the InnoDB storage engine. In this case, the server will not start if the default storage engine is set to InnoDB. Use --default-storage-engine to set the default to some other engine if necessary.

• --skip-merge

  Disable the MERGE storage engine. This option was added in MySQL 5.0.24. It can be used if the following behavior is undesirable: If a user has access to MyISAM table t, that user can create a MERGE table m that accesses t. However, if the user's privileges on t are subsequently revoked, the user can continue to access t by doing so through m.

• --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 8.12.6.2, “DNS Lookup Optimization and the Host Cache”.

  Depending on the network configuration of your system and the Host values for your accounts, clients may need to connect using an explicit --host option, such as --host=localhost or --host=127.0.0.1.

• --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 8.12.6.2, “DNS Lookup Optimization and the Host Cache”.

• --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 6.3.6.5, “SSL Command Options”.

• --standalone

  Command-Line Format	--standalone
  Platform Specific	Windows

  Instructs the MySQL server not to run as a service.

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

  Command-Line 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 8.12.4.3, “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 8.12.4.2, “Using Symbolic Links for MyISAM Tables on Unix”.

• --skip-safemalloc

  Command-Line 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 do not need it by using the --skip-safemalloc option.

• --skip-show-database

  Command-Line 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

  Do not write stack traces. This option is useful when you are running mysqld under a debugger. On some systems, you also must use this option to get a core file. See Section 21.3, “Debugging and Porting MySQL”.

• --skip-thread-priority

  Command-Line Format

  --skip-thread-priority

  Disable using thread priorities for faster response time.

  mysqld makes a large number of invalid calls to thread scheduling routines on Linux. These calls do not affect performance noticeably but may be a source of “noise” for debugging tools. For example, they can overwhelm other information of more interest in kernel logs. To avoid these calls, start the server with the --skip-thread-priority option.

• --socket=path

  Command-Line Format	--socket={file_name|pipe_name}
  System Variable	Name	socket
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	string
  	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
  System Variable	Name	sql_mode
  	Variable Scope	Global, Session
  	Dynamic Variable	Yes
  Permitted Values	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”.

  Note

  MySQL installation programs may configure the SQL mode during the installation process. If the SQL mode differs from the default or from what you expect, check for a setting in an option file that the server reads at startup.

• --sysdate-is-now

  Introduced	5.0.20
  Command-Line Format	--sysdate-is-now
  Permitted Values	Type	boolean
  	Default	FALSE

  As of MySQL 5.0.12, 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”.

  This option was added in MySQL 5.0.20.

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

  Introduced	5.0.3
  Command-Line Format	--tc-heuristic-recover=name
  Permitted Values	Type	enumeration
  	Default	COMMIT
  	Valid Values	COMMIT
  		ROLLBACK

  The type of decision to use in the heuristic recovery process. This option is unused. Added in MySQL 5.0.3.

• --temp-pool

  Command-Line 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.

• --transaction-isolation=level

  Command-Line Format	--transaction-isolation=name
  Permitted Values	Type	enumeration
  	Default	REPEATABLE-READ
  	Valid Values	READ-UNCOMMITTED
  		READ-COMMITTED
  		REPEATABLE-READ
  		SERIALIZABLE

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

• --tmpdir=dir_name, -t dir_name

  Command-Line Format	--tmpdir=dir_name
  System Variable	Name	tmpdir
  	Variable Scope	Global
  	Dynamic Variable	No
  Permitted Values	Type	directory name

  The path of the directory to use for creating temporary files. It might be useful if your default /tmp directory resides on a partition that is too small to hold temporary tables. This option accepts several paths that are used in round-robin fashion. Paths should be separated by colon characters (“:”) on Unix and semicolon characters (“;”) on Windows, 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.5.3.5, “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
  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

  System Variable	Name	version
  	Variable Scope	Global
  	Dynamic Variable	No

  Display version information and exit.

  An attempt to connect to the host 127.0.0.1 normally resolves to the localhost account. However, this fails if the server is run with the --skip-name-resolve option, so make sure that an account exists that can accept a connection. For example, to be able to connect as root using --host=127.0.0.1 or --host=::1, create these accounts:

  CREATE USER 'root'@'127.0.0.1' IDENTIFIED BY 'root-password';
  CREATE USER 'root'@'::1' IDENTIFIED BY 'root-password';