5.1.6 Server Command Options
When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.2, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 4.2.2.2, “Using Option Files”. That section also describes option file format and syntax.
mysqld reads options from the [mysqld]
and [server]
groups. mysqld_safe reads options from the [mysqld]
, [server]
, [mysqld_safe]
, and [safe_mysqld]
groups. mysql.server reads options from the [mysqld]
and [mysql.server]
groups.
An embedded MySQL server usually reads options from the [server]
, [embedded]
, and [
groups, where xxxxx
_SERVER]xxxxx
is the name of the application into which the server is embedded.
mysqld accepts many command options. For a brief summary, execute this command:
mysqld --help
To see the full list, use this command:
mysqld --verbose --help
Some of the items in the list are actually system variables that can be set at server startup. These can be displayed at runtime using the SHOW VARIABLES
statement. Some items displayed by the preceding mysqld command do not appear in SHOW VARIABLES
output; this is because they are options only and not system variables.
The following list shows some of the most common server options. Additional options are described in other sections:
Options that affect security: See Section 6.1.4, “Security-Related mysqld Options and Variables”.
SSL-related options: See Command Options for Encrypted Connections.
Binary log control options: See Section 5.4.4, “The Binary Log”.
Replication-related options: See Section 16.1.6, “Replication and Binary Logging Options and Variables”.
Options for loading plugins such as pluggable storage engines: See Section 5.5.1, “Installing and Uninstalling Plugins”.
Options specific to particular storage engines: See Section 14.15, “InnoDB Startup Options and System Variables” and Section 15.2.1, “MyISAM Startup Options”.
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 --
. For example, var_name
=value
--sort_buffer_size=384M
sets the sort_buffer_size
variable to a value of 384MB.
When you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.
To restrict the maximum value to which a system variable can be set at runtime with the SET
statement, specify this maximum by using an option of the form --maximum-
at server startup. var_name
=value
You can change the values of most system variables at runtime with the SET
statement. See Section 13.7.4.1, “SET Syntax for Variable Assignment”.
Section 5.1.7, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. For information on changing system variables, see Section 5.1.1, “Configuring the Server”.
--help
,-?
Property Value Command-Line Format --help
Display a short help message and exit. Use both the
--verbose
and--help
options to see the full message.-
Property Value Command-Line Format --allow-suspicious-udfs[={OFF|ON}]
Type Boolean Default Value OFF
This option controls whether user-defined functions that have only an
xxx
symbol for the main function can be loaded. By default, the option is off and only UDFs that have at least one auxiliary symbol can be loaded; this prevents attempts at loading functions from shared object files other than those containing legitimate UDFs. See UDF Security Precautions. -
Property Value Command-Line Format --ansi
Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise control over the server SQL mode, use the
--sql-mode
option instead. See Section 1.8, “MySQL Standards Compliance”, and Section 5.1.10, “Server SQL Modes”. --basedir=
,dir_name
-b
dir_name
Property Value Command-Line Format --basedir=dir_name
System Variable basedir
Scope Global Dynamic No Type Directory name Default Value configuration-dependent default
The path to the MySQL installation directory. This option sets the
basedir
system variable.-
Property Value Command-Line Format --bootstrap
Deprecated Yes This option is used by the mysql_install_db program to create the MySQL privilege tables without having to start a full MySQL server.
Notemysql_install_db is deprecated because its functionality has been integrated into mysqld, the MySQL server. Consequently, the
--bootstrap
server option that mysql_install_db passes to mysqld is also deprecated. To initialize a MySQL installation, invoke mysqld with the--initialize
or--initialize-insecure
option. For more information, see Section 2.10.1, “Initializing the Data Directory”. mysql_install_db and the--bootstrap
server option will be removed in a future MySQL release.--bootstrap
is mutually exclusive with--daemonize
,--initialize
, and--initialize-insecure
.Global transaction identifiers (GTIDs) are not disabled when
--bootstrap
is used.--bootstrap
was used (Bug #20980271). See Section 16.1.3, “Replication with Global Transaction Identifiers”.When the server operates in bootstap mode, some functionality is unavailable that limits the statements permitted in any file named by the
init_file
system variable. For more information, see the description of that variable. In addition, thedisabled_storage_engines
system variable has no effect. --character-set-client-handshake
Property Value Command-Line Format --character-set-client-handshake[={OFF|ON}]
Type Boolean Default Value ON
Do not ignore character set information sent by the client. To ignore client information and use the default server character set, use
--skip-character-set-client-handshake
; this makes MySQL behave like MySQL 4.0.--chroot=
,dir_name
-r
dir_name
Property Value Command-Line Format --chroot=dir_name
Type Directory name Put the mysqld server in a closed environment during startup by using the
chroot()
system call. This is a recommended security measure. Use of this option somewhat limitsLOAD DATA
andSELECT ... INTO OUTFILE
.-
Property Value Command-Line Format --console
Platform Specific Windows (Windows only.) Write the error log to
stderr
andstdout
(the console). mysqld does not close the console window if this option is used.--console
takes precedence over--log-error
if both are given. (In MySQL 5.5 and 5.6, this is reversed:--log-error
takes precedence over--console
if both are given.) -
Property Value Command-Line Format --core-file[={OFF|ON}]
Type Boolean Default Value OFF
Write a core file if mysqld dies. The name and location of the core file is system dependent. On Linux, a core file named
core.
is written to the current working directory of the process, which for mysqld is the data directory.pid
pid
represents the process ID of the server process. On macOS, a core file namedcore.
is written to thepid
/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. -
Property Value Command-Line Format --daemonize[={OFF|ON}]
Type Boolean Default Value OFF
This option causes the server to run as a traditional, forking daemon, permitting it to work with operating systems that use systemd for process control. For more information, see Section 2.5.10, “Managing MySQL Server with systemd”.
--daemonize
is mutually exclusive with--bootstrap
,--initialize
, and--initialize-insecure
. --datadir=
,dir_name
-h
dir_name
Property Value Command-Line Format --datadir=dir_name
System Variable datadir
Scope Global Dynamic No Type Directory name The path to the MySQL server data directory. This option sets the
datadir
system variable. See the description of that variable.--debug[=
,debug_options
]-# [
debug_options
]Property Value Command-Line Format --debug[=debug_options]
System Variable debug
Scope Global, Session Dynamic Yes Type String Default Value (Windows) d:t:i:O,\mysqld.trace
Default Value (Unix) d:t:i:o,/tmp/mysqld.trace
If MySQL is configured with the
-DWITH_DEBUG=1
CMake option, you can use this option to get a trace file of what mysqld is doing. A typicaldebug_options
string isd:t:o,
. The default isfile_name
d:t:i:o,/tmp/mysqld.trace
on Unix andd:t:i:O,\mysqld.trace
on Windows.Using
-DWITH_DEBUG=1
to configure MySQL with debugging support enables you to use the--debug="d,parser_debug"
option when you start the server. This causes the Bison parser that is used to process SQL statements to dump a parser trace to the server's standard error output. Typically, this output is written to the error log.This option may be given multiple times. Values that begin with
+
or-
are added to or subtracted from the previous value. For example,--debug=T
--debug=+P
sets the value toP:T
.For more information, see Section 28.5.3, “The DBUG Package”.
-
Property Value Command-Line Format --debug-sync-timeout[=#]
Type Integer Controls whether the Debug Sync facility for testing and debugging is enabled. Use of Debug Sync requires that MySQL be configured with the
-DENABLE_DEBUG_SYNC=1
CMake option (see Section 2.9.7, “MySQL Source-Configuration Options”). If Debug Sync is not compiled in, this option is not available. The option value is a timeout in seconds. The default value is 0, which disables Debug Sync. To enable it, specify a value greater than 0; this value also becomes the default timeout for individual synchronization points. If the option is given without a value, the timeout is set to 300 seconds.For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization .
-
Property Value Command-Line Format --default-time-zone=name
Type String Set the default server time zone. This option sets the global
time_zone
system variable. If this option is not given, the default time zone is the same as the system time zone (given by the value of thesystem_time_zone
system variable. --defaults-extra-file=
file_name
Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs.
file_name
is interpreted relative to the current directory if given as a relative path name rather than a full path name. This must be the first option on the command line if it is used.For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.
Read only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs.
file_name
is interpreted relative to the current directory if given as a relative path name rather than a full path name.NoteThis must be the first option on the command line if it is used, except that if the server is started with the
--defaults-file
and--install
(or--install-manual
) options,--install
(or--install-manual
) must be first.For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.
Read not only the usual option groups, but also groups with the usual names and a suffix of
str
. For example, mysqld normally reads the[mysqld]
group. If the--defaults-group-suffix=_other
option is given, mysqld also reads the[mysqld_other]
group.For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.
-
Property Value Command-Line Format --des-key-file=file_name
Deprecated Yes Read the default DES keys from this file. These keys are used by the
DES_ENCRYPT()
andDES_DECRYPT()
functions.NoteThe
DES_ENCRYPT()
andDES_DECRYPT()
functions are deprecated in MySQL 5.7, will be removed in a future MySQL release, and should no longer be used. Consequently,--des-key-file
also is deprecated and will be removed. --disable-partition-engine-check
Property Value Command-Line Format --disable-partition-engine-check[={OFF|ON}]
Introduced 5.7.17 Deprecated 5.7.17 Type Boolean Default Value (≥ 5.7.21) ON
Default Value (≥ 5.7.17, ≤ 5.7.20) OFF
Whether to disable the startup check for tables with nonnative partitioning.
As of MySQL 5.7.17, the generic partitioning handler in the MySQL server is deprecated, and is removed in MySQL 8.0, when the storage engine used for a given table is expected to provide its own (“native”) partitioning handler. Currently, only the
InnoDB
andNDB
storage engines do this.Use of tables with nonnative partitioning results in an
ER_WARN_DEPRECATED_SYNTAX
warning. In MySQL 5.7.17 through 5.7.20, the server automatically performs a check at startup to identify tables that use nonnative partitioning; for any that are found, the server writes a message to its error log. To disable this check, use the--disable-partition-engine-check
option. In MySQL 5.7.21 and later, this check is not performed; in these versions, you must start the server with--disable-partition-engine-check=false
, if you wish for the server to check for tables using the generic partitioning handler (Bug #85830, Bug #25846957).Use of tables with nonnative partitioning results in an
ER_WARN_DEPRECATED_SYNTAX
warning. Also, the server performs a check at startup to identify tables that use nonnative partitioning; for any found, the server writes a message to its error log. To disable this check, use the--disable-partition-engine-check
option.To prepare for migration to MySQL 8.0, any table with nonnative partitioning should be changed to use an engine that provides native partitioning, or be made nonpartitioned. For example, to change a table to
InnoDB
, execute this statement:ALTER TABLE table_name ENGINE = INNODB;
--early-plugin-load=
plugin_list
Property Value Command-Line Format --early-plugin-load=plugin_list
Introduced 5.7.11 Type String Default Value (≥ 5.7.12) empty string
Default Value (5.7.11) keyring_file plugin library file name
This option tells the server which plugins to load before loading mandatory built-in plugins and before storage engine initialization. If multiple
--early-plugin-load
options are given, only the last one is used.The option value is a semicolon-separated list of
name
=
plugin_library
andplugin_library
values. Eachname
is the name of a plugin to load, andplugin_library
is the name of the library file that contains the plugin code. If a plugin library is named without any preceding plugin name, the server loads all plugins in the library. The server looks for plugin library files in the directory named by theplugin_dir
system variable.For example, if plugins named
myplug1
andmyplug2
have library filesmyplug1.so
andmyplug2.so
, use this option to perform an early plugin load:shell> mysqld --early-plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
Quotes are used around the argument value because otherwise a semicolon (
;
) is interpreted as a special character by some command interpreters. (Unix shells treat it as a command terminator, for example.)Each named plugin is loaded early for a single invocation of mysqld only. After a restart, the plugin is not loaded early unless
--early-plugin-load
is used again.If the server is started using
--initialize
or--initialize-insecure
, plugins specified by--early-plugin-load
are not loaded.If the server is run with
--help
, plugins specified by--early-plugin-load
are loaded but not initialized. This behavior ensures that plugin options are displayed in the help message.As of MySQL 5.7.12, the default
--early-plugin-load
value is empty. To load your chosen keyring plugin, you must use an explicit--early-plugin-load
option with a nonempty value.ImportantIn MySQL 5.7.11, the default
--early-plugin-load
value was the name of thekeyring_file
plugin library file, so that plugin was loaded by default.InnoDB
tablespace encryption requires thekeyring_file
plugin to be loaded prior toInnoDB
initialization, so this change of default--early-plugin-load
value introduces an incompatibility for upgrades from 5.7.11 to 5.7.12 or higher. Administrators who have encryptedInnoDB
tablespaces must take explicit action to ensure continued loading of thekeyring_file
plugin: Start the server with an--early-plugin-load
option that names the plugin library file. For additional information, see Section 6.4.4.1, “Keyring Plugin Installation”.The
InnoDB
tablespace encryption feature relies on thekeyring_file
plugin for encryption key management, and thekeyring_file
plugin must be loaded prior to storage engine initialization to facilitateInnoDB
recovery for encrypted tables. In MySQL 5.7.11, if you do not want to load thekeyring_file
plugin at server startup, specify an empty string (--early-plugin-load=""
).For information about
InnoDB
tablespace encryption, see Section 14.14, “InnoDB Data-at-Rest Encryption”. For general information about plugin loading, see Section 5.5.1, “Installing and Uninstalling Plugins”.--exit-info[=
,flags
]-T [
flags
]Property Value Command-Line Format --exit-info[=flags]
Type Integer This is a bitmask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!
-
Property Value Command-Line Format --external-locking[={OFF|ON}]
Type Boolean Default Value OFF
Enable external locking (system locking), which is disabled by default. If you use this option on a system on which
lockd
does not fully work (such as Linux), it is easy for mysqld to deadlock.To disable external locking explicitly, use
--skip-external-locking
.External locking affects only
MyISAM
table access. For more information, including conditions under which it can and cannot be used, see Section 8.11.5, “External Locking”. -
Property Value Command-Line Format --flush[={OFF|ON}]
System Variable flush
Scope Global Dynamic Yes Type Boolean Default Value OFF
Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.4.3.3, “What to Do If MySQL Keeps Crashing”.
NoteIf
--flush
is specified, the value offlush_time
does not matter and changes toflush_time
have no effect on flush behavior. -
Property Value Command-Line Format --gdb[={OFF|ON}]
Type Boolean Default Value OFF
Install an interrupt handler for
SIGINT
(needed to stop mysqld with^C
to set breakpoints) and disable stack tracing and core file handling. See Section 28.5.1.4, “Debugging mysqld under gdb”. -
Property Value Command-Line Format --ignore-db-dir=dir_name
Deprecated 5.7.16 Type Directory name This option tells the server to ignore the given directory name for purposes of the
SHOW DATABASES
statement orINFORMATION_SCHEMA
tables. For example, if a MySQL configuration locates the data directory at the root of a file system on Unix, the system might create alost+found
directory there that the server should ignore. Starting the server with--ignore-db-dir=lost+found
causes that name not to be listed as a database.To specify more than one name, use this option multiple times, once for each name. Specifying the option with an empty value (that is, as
--ignore-db-dir=
) resets the directory list to the empty list.Instances of this option given at server startup are used to set the
ignore_db_dirs
system variable.This option is deprecated in MySQL 5.7. With the introduction of the data dictionary in MySQL 8.0, it became superfluous and was removed in that version.
-
Property Value Command-Line Format --initialize[={OFF|ON}]
Type Boolean Default Value OFF
This option is used to initialize a MySQL installation by creating the data directory and populating the tables in the
mysql
system database. For more information, see Section 2.10.1, “Initializing the Data Directory”.When the server is started with
--initialize
, some functionality is unavailable that limits the statements permitted in any file named by theinit_file
system variable. For more information, see the description of that variable. In addition, thedisabled_storage_engines
system variable has no effect.In MySQL NDB Cluster 7.5.4 and later, the
--ndbcluster
option is ignored when used together with--initialize
. (Bug #81689, Bug #23518923)--initialize
is mutually exclusive with--bootstrap
and--daemonize
. -
Property Value Command-Line Format --initialize-insecure[={OFF|ON}]
Type Boolean Default Value OFF
This option is used to initialize a MySQL installation by creating the data directory and populating the tables in the
mysql
system database. This option implies--initialize
. For more information, see the description of that option, and Section 2.10.1, “Initializing the Data Directory”.--initialize-insecure
is mutually exclusive with--bootstrap
and--daemonize
. --innodb-
xxx
Set an option for the
InnoDB
storage engine. TheInnoDB
options are listed in Section 14.15, “InnoDB Startup Options and System Variables”.-
Property Value Command-Line Format --install [service_name]
Platform Specific Windows (Windows only) Install the server as a Windows service that starts automatically during Windows startup. The default service name is
MySQL
if noservice_name
value is given. For more information, see Section 2.3.4.8, “Starting MySQL as a Windows Service”.NoteIf the server is started with the
--defaults-file
and--install
options,--install
must be first. --install-manual [
service_name
]Property Value Command-Line Format --install-manual [service_name]
Platform Specific Windows (Windows only) Install the server as a Windows service that must be started manually. It does not start automatically during Windows startup. The default service name is
MySQL
if noservice_name
value is given. For more information, see Section 2.3.4.8, “Starting MySQL as a Windows Service”.NoteIf the server is started with the
--defaults-file
and--install-manual
options,--install-manual
must be first.--language=
lang_name
, -Llang_name
Property Value Command-Line Format --language=name
Deprecated Yes; use lc-messages-dir
insteadSystem Variable language
Scope Global Dynamic No Type Directory name Default Value /usr/local/mysql/share/mysql/english/
The language to use for error messages.
lang_name
can be given as the language name or as the full path name to the directory where the language files are installed. See Section 10.12, “Setting the Error Message Language”.--lc-messages-dir
and--lc-messages
should be used rather than--language
, which is deprecated (and handled as a synonym for--lc-messages-dir
). The--language
option will be removed in a future MySQL release.-
Property Value Command-Line Format --large-pages[={OFF|ON}]
System Variable large_pages
Scope Global Dynamic No Platform Specific Linux Type Boolean Default Value OFF
Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.
MySQL supports the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.12.4.2, “Enabling Large Page Support”. For Solaris support of large pages, see the description of the
--super-large-pages
option.--large-pages
is disabled by default. -
Property Value Command-Line Format --lc-messages=name
System Variable lc_messages
Scope Global, Session Dynamic Yes Type String Default Value en_US
The locale to use for error messages. The default is
en_US
. The server converts the argument to a language name and combines it with the value of--lc-messages-dir
to produce the location for the error message file. See Section 10.12, “Setting the Error Message Language”. -
Property Value Command-Line Format --lc-messages-dir=dir_name
System Variable lc_messages_dir
Scope Global Dynamic No Type Directory name The directory where error messages are located. The server uses the value together with the value of
--lc-messages
to produce the location for the error message file. See Section 10.12, “Setting the Error Message Language”. -
Property Value Command-Line Format --local-service
(Windows only) A
--local-service
option following the service name causes the server to run using theLocalService
Windows account that has limited system privileges. If both--defaults-file
and--local-service
are given following the service name, they can be in any order. See Section 2.3.4.8, “Starting MySQL as a Windows Service”. -
Property Value Command-Line Format --log-error[=file_name]
System Variable log_error
Scope Global Dynamic No Type File name Write the error log and startup messages to this file. See Section 5.4.2, “The Error Log”.
If the option names no file, the error log file name on Unix and Unix-like systems is
in the data directory. The file name on Windows is the same, unless thehost_name
.err--pid-file
option is specified. In that case, the file name is the PID file base name with a suffix of.err
in the data directory.If the option names a file, the error log file has that name (with an
.err
suffix added if the name has no suffix), located under the data directory unless an absolute path name is given to specify a different location.On Windows,
--console
takes precedence over--log-error
if both are given. In this case, the server writes the error log to the console rather than to a file. (In MySQL 5.5 and 5.6, this is reversed:--log-error
takes precedence over--console
if both are given.) -
Property Value Command-Line Format --log-isam[=file_name]
Type File name Log all
MyISAM
changes to this file (used only when debuggingMyISAM
). -
Property Value Command-Line Format --log-raw[={OFF|ON}]
Type Boolean Default Value OFF
Passwords in certain statements written to the general query log, slow query log, and binary log are rewritten by the server not to occur literally in plain text. Password rewriting can be suppressed for the general query log by starting the server with the
--log-raw
option. This option may be useful for diagnostic purposes, to see the exact text of statements as received by the server, but for security reasons is not recommended for production use.If a query rewrite plugin is installed, the
--log-raw
option affects statement logging as follows:For more information, see Section 6.1.2.3, “Passwords and Logging”.
-
Property Value Command-Line Format --log-short-format[={OFF|ON}]
Type Boolean Default Value OFF
Log less information to the slow query log, if it has been activated.
-
Property Value Command-Line Format --log-tc=file_name
Type File name Default Value tc.log
The name of the memory-mapped transaction coordinator log file (for XA transactions that affect multiple storage engines when the binary log is disabled). The default name is
tc.log
. The file is created under the data directory if not given as a full path name. This option is unused. -
Property Value Command-Line Format --log-tc-size=#
Type Integer Default Value (64-bit platforms, ≥ 5.7.21) 6 * page size
Default Value (64-bit platforms, ≤ 5.7.20) 24576
Default Value (32-bit platforms, ≥ 5.7.21) 6 * page size
Default Value (32-bit platforms, ≤ 5.7.20) 24576
Minimum Value 6 * page size
Maximum Value (64-bit platforms) 18446744073709551615
Maximum Value (32-bit platforms) 4294967295
The size in bytes of the memory-mapped transaction coordinator log. The default and minimum values are 6 times the page size, and the value must be a multiple of the page size. (Before MySQL 5.7.21, the default size is 24KB.)
--log-warnings[=
,level
]-W [
level
]Property Value Command-Line Format --log-warnings[=#]
Deprecated Yes System Variable log_warnings
Scope Global Dynamic Yes Type Integer Default Value 2
Minimum Value 0
Maximum Value (64-bit platforms) 18446744073709551615
Maximum Value (32-bit platforms) 4294967295
NoteThe
log_error_verbosity
system variable is preferred over, and should be used instead of, the--log-warnings
option orlog_warnings
system variable. For more information, see the descriptions oflog_error_verbosity
andlog_warnings
. The--log-warnings
command-line option andlog_warnings
system variable are deprecated and will be removed in a future MySQL release.Whether to produce additional warning messages to the error log. This option is enabled by default. To disable it, use
--log-warnings=0
. Specifying the option without alevel
value increments the current value by 1. The server logs messages about statements that are unsafe for statement-based logging if the value is greater than 0. Aborted connections and access-denied errors for new connection attempts are logged if the value is greater than 1. See Section B.4.2.10, “Communication Errors and Aborted Connections”.-
Property Value Command-Line Format --memlock[={OFF|ON}]
Type Boolean Default Value OFF
Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.
--memlock
works on systems that support themlockall()
system call; this includes Solaris, most Linux distributions that use a 2.4 or higher kernel, and perhaps other Unix systems. On Linux systems, you can tell whether or notmlockall()
(and thus this option) is supported by checking to see whether or not it is defined in the systemmman.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;
ImportantUse 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 thelimits.conf
file. See the notes regarding the memlock limit in Section 8.12.4.2, “Enabling Large Page Support”.You must not try to use this option on a system that does not support the
mlockall()
system call; if you do so, mysqld will very likely crash as soon as you try to start it. -
Property Value Command-Line Format --myisam-block-size=#
Type Integer Default Value 1024
Minimum Value 1024
Maximum Value 16384
The block size to be used for
MyISAM
index pages. Do not read any option files. If program startup fails due to reading unknown options from an option file,
--no-defaults
can be used to prevent them from being read. This must be the first option on the command line if it is used.For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.
-
Property Value Command-Line Format --old-style-user-limits[={OFF|ON}]
Type Boolean Default Value OFF
Enable old-style user limits. (Before MySQL 5.0.3, account resource limits were counted separately for each host from which a user connected rather than per account row in the
user
table.) See Section 6.2.16, “Setting Account Resource Limits”. -
Property Value Command-Line Format --partition[={OFF|ON}]
Deprecated 5.7.16 Disabled by skip-partition
Type Boolean Default Value ON
Enables or disables user-defined partitioning support in the MySQL Server.
This option is deprecated in MySQL 5.7.16, and is removed from MySQL 8.0 because in MySQL 8.0, the partitioning engine is replaced by native partitioning, which cannot be disabled.
--performance-schema-xxx
Configure a Performance Schema option. For details, see Section 25.14, “Performance Schema Command Options”.
-
Property Value Command-Line Format --plugin-load=plugin_list
System Variable plugin_load
Scope Global Dynamic No Type String This option tells the server to load the named plugins at startup. If multiple
--plugin-load
options are given, only the last one is used. Additional plugins to load may be specified using--plugin-load-add
options.The option value is a semicolon-separated list of
name
=
plugin_library
andplugin_library
values. Eachname
is the name of a plugin to load, andplugin_library
is the name of the library file that contains the plugin code. If a plugin library is named without any preceding plugin name, the server loads all plugins in the library. The server looks for plugin library files in the directory named by theplugin_dir
system variable.For example, if plugins named
myplug1
andmyplug2
have library filesmyplug1.so
andmyplug2.so
, use this option to perform an early plugin load:shell> mysqld --plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
Quotes are used around the argument value here because otherwise semicolon (
;
) is interpreted as a special character by some command interpreters. (Unix shells treat it as a command terminator, for example.)Each named plugin is loaded for a single invocation of mysqld only. After a restart, the plugin is not loaded unless
--plugin-load
is used again. This is in contrast toINSTALL PLUGIN
, which adds an entry to themysql.plugins
table to cause the plugin to be loaded for every normal server startup.Under normal startup, the server determines which plugins to load by reading the
mysql.plugins
system table. If the server is started with the--skip-grant-tables
option, it does not consult themysql.plugins
table and does not load plugins listed there.--plugin-load
enables plugins to be loaded even when--skip-grant-tables
is given.--plugin-load
also enables plugins to be loaded at startup that cannot be loaded at runtime.For additional information about plugin loading, see Section 5.5.1, “Installing and Uninstalling Plugins”.
-
Property Value Command-Line Format --plugin-load-add=plugin_list
System Variable plugin_load_add
Scope Global Dynamic No Type String This option complements the
--plugin-load
option.--plugin-load-add
adds a plugin or plugins to the set of plugins to be loaded at startup. The argument format is the same as for--plugin-load
.--plugin-load-add
can be used to avoid specifying a large set of plugins as a single long unwieldy--plugin-load
argument.--plugin-load-add
can be given in the absence of--plugin-load
, but any instance of--plugin-load-add
that appears before--plugin-load
. has no effect because--plugin-load
resets the set of plugins to load. In other words, these options:--plugin-load=x --plugin-load-add=y
are equivalent to this option:
--plugin-load="x;y"
But these options:
--plugin-load-add=y --plugin-load=x
are equivalent to this option:
--plugin-load=x
For additional information about plugin loading, see Section 5.5.1, “Installing and Uninstalling Plugins”.
Specifies an option that pertains to a server plugin. For example, many storage engines can be built as plugins, and for such engines, options for them can be specified with a
--plugin
prefix. Thus, the--innodb-file-per-table
option forInnoDB
can be specified as--plugin-innodb-file-per-table
.For boolean options that can be enabled or disabled, the
--skip
prefix and other alternative formats are supported as well (see Section 4.2.2.4, “Program Option Modifiers”). For example,--skip-plugin-innodb-file-per-table
disablesinnodb-file-per-table
.The rationale for the
--plugin
prefix is that it enables plugin options to be specified unambiguously if there is a name conflict with a built-in server option. For example, were a plugin writer to name a plugin “sql” and implement a “mode” option, the option name might be--sql-mode
, which would conflict with the built-in option of the same name. In such cases, references to the conflicting name are resolved in favor of the built-in option. To avoid the ambiguity, users can specify the plugin option as--plugin-sql-mode
. Use of the--plugin
prefix for plugin options is recommended to avoid any question of ambiguity.--port=
,port_num
-P
port_num
Property Value Command-Line Format --port=port_num
System Variable port