MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
When you start the mysqld server, you can specify program options using any of the methods described in Section 6.2.2, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 6.2.2.2, “Using Option Files”. That section also describes option file format and syntax.
mysqld reads options from the
[mysqld] and [server]
groups. mysqld_safe reads options from the
[mysqld], [server],
[mysqld_safe], and
[safe_mysqld] groups.
mysql.server reads options from the
[mysqld] and [mysql.server]
groups.
mysqld accepts many command options. For a brief summary, execute this command:
mysqld --help
To see the full list, use this command:
mysqld --verbose --help
Some of the items in the list are actually system variables that
can be set at server startup. These can be displayed at runtime
using the SHOW VARIABLES statement.
Some items displayed by the preceding mysqld
command do not appear in SHOW
VARIABLES output; this is because they are options only
and not system variables.
The following list shows some of the most common server options. Additional options are described in other sections:
Options that affect security: See Section 8.1.4, “Security-Related mysqld Options and Variables”.
SSL-related options: See Command Options for Encrypted Connections.
Binary log control options: See Section 7.4.4, “The Binary Log”.
Replication-related options: See Section 19.1.6, “Replication and Binary Logging Options and Variables”.
Options for loading plugins such as pluggable storage engines: See Section 7.6.1, “Installing and Uninstalling Plugins”.
Options specific to particular storage engines: See Section 17.14, “InnoDB Startup Options and System Variables” and Section 18.2.1, “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 adjusts a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server sets the value to 1024.
Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.
Some options take file name values. Unless otherwise specified,
the default file location is the data directory if the value is a
relative path name. To specify the location explicitly, use an
absolute path name. Suppose that the data directory is
/var/mysql/data. If a file-valued option is
given as a relative path name, it is located under
/var/mysql/data. If the value is an absolute
path name, its location is as given by the path name.
You can also set the values of server system variables at server
startup by using variable names as options. To assign a value to a
server system variable, use an option of the form
--.
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 15.7.6.1, “SET Syntax for Variable Assignment”.
Section 7.1.8, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. For information on changing system variables, see Section 7.1.1, “Configuring the Server”.
--help, -?
| Command-Line Format | --help |
|---|
Display a short help message and exit. Use both the
--verbose and
--help options to see the full
message.
| Command-Line Format | --allow-suspicious-udfs[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
This option controls whether loadable functions that have only
an xxx symbol for the main function can be
loaded. By default, the option is off and only loadable
functions that have at least one auxiliary symbol can be
loaded; this prevents attempts at loading functions from
shared object files other than those containing legitimate
functions. See Loadable Function Security Precautions.
| 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 1.7, “MySQL Standards Compliance”, and
Section 7.1.11, “Server SQL Modes”.
--basedir=,
dir_name-b
dir_name
| Command-Line Format | --basedir=dir_name |
|---|---|
| System Variable | basedir |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Directory name |
| Default Value | parent of mysqld installation directory |
The path to the MySQL installation directory. This option sets
the basedir system variable.
The server executable determines its own full path name at
startup and uses the parent of the directory in which it is
located as the default
basedir value. This in turn
enables the server to use that
basedir when searching for
server-related information such as the
share directory containing error
messages.
| Command-Line Format | --check-table-functions=value |
|---|---|
| Type | Enumeration |
| Default Value | ABORT |
| Valid Values |
|
When performing an upgade of the server, we scan the data
dictionary for functions used in table constraints and other
expressions, including DEFAULT expressions,
partitioning expressions, and virtual columns. It is possible
that a change in the behavior of the function causes it to
raise an error in the new version of the server, where no such
error occurred before in which case the table cannot be
opened. This option provides a choice in how to handle such
problems, according to which of the two values shown here is
used:
WARN: Log a warning for each table that
cannot be opened.
ABORT: Also logs a warning; in
addition, the upgrade is stopped. This is the default. For
a sufficiently high value of
--log-error-verbosity, it
also logs a note with a streamlined table definition
listing only those expressions that potentially contain
SQL functions.
The default behaviour is to abort the upgrade, so that the
user can fix the issue using the older version of the server,
before upgrading to the newer one. Use WARN
to continue the upgrade in interactive mode while reporting
any issues.
The --check-table-functions option was
introduced in MySQL 9.3.0.
--chroot=,
dir_name-r
dir_name
| Command-Line Format | --chroot=dir_name |
|---|---|
| Type | Directory name |
Put the mysqld server in a closed
environment during startup by using the
chroot() system call. This is a recommended
security measure. Use of this option somewhat limits
LOAD DATA and
SELECT ... INTO
OUTFILE.
| Command-Line Format | --console |
|---|---|
| Platform Specific | Windows |
(Windows only.) Cause the default error log destination to be the console. This affects log sinks that base their own output destination on the default destination. See Section 7.4.2, “The Error Log”. mysqld does not close the console window if this option is used.
--console takes precedence over
--log-error if both are given.
| Command-Line Format | --core-file |
|---|
When this option is used, write a core file if
mysqld dies; no arguments are needed (or
accepted). The name and location of the core file is system
dependent. On Linux, a core file named
core. is
written to the current working directory of the process, which
for mysqld is the data directory.
pidpid represents the process ID of
the server process. On macOS, a core file named
core. is
written to the pid/cores directory. On
Solaris, use the coreadm command to specify
where to write the core file and how to name it.
For some systems, to get a core file you must also specify the
--core-file-size option to
mysqld_safe. See
Section 6.3.2, “mysqld_safe — MySQL Server Startup Script”. On some systems, such as
Solaris, you do not get a core file if you are also using the
--user option. There might be
additional restrictions or limitations. For example, it might
be necessary to execute ulimit -c unlimited
before starting the server. Consult your system documentation.
The
innodb_buffer_pool_in_core_file
variable can be used to reduce the size of core files on
operating systems that support it. For more information, see
Section 17.8.3.7, “Excluding or Including Buffer Pool Pages from Core Files”.
--daemonize,
-D
| Command-Line Format | --daemonize[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
This option causes the server to run as a traditional, forking daemon, permitting it to work with operating systems that use systemd for process control. For more information, see Section 2.5.9, “Managing MySQL Server with systemd”.
--daemonize is mutually
exclusive with --initialize and
--initialize-insecure.
If the server is started using the
--daemonize option and is not connected to a
tty device, a default error logging option of
--log-error="" is used in the absence of an
explicit logging option, to direct error output to the default
log file.
-D is a synonym for
--daemonize.
--datadir=,
dir_name-h
dir_name
| Command-Line Format | --datadir=dir_name |
|---|---|
| System Variable | datadir |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Directory name |
The path to the MySQL server data directory. This option sets
the datadir system variable.
See the description of that variable.
--debug[=,
debug_options]-# [
debug_options]
| Command-Line Format | --debug[=debug_options] |
|---|---|
| System Variable | debug |
| Scope | Global, Session |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | String |
| Default Value (Unix) | d:t:i:o,/tmp/mysqld.trace |
| Default Value (Windows) | d:t:i:O,\mysqld.trace |
If MySQL is configured with the
-DWITH_DEBUG=1
CMake option, you can use this option to
get a trace file of what mysqld is doing. A
typical debug_options string is
d:t:o,.
The default is file_named:t:i:o,/tmp/mysqld.trace on
Unix and d:t:i:O,\mysqld.trace on Windows.
Using -DWITH_DEBUG=1 to
configure MySQL with debugging support enables you to use the
--debug="d,parser_debug" option
when you start the server. This causes the Bison parser that
is used to process SQL statements to dump a parser trace to
the server's standard error output. Typically, this output is
written to the error log.
This option may be given multiple times. Values that begin
with + or - are added to
or subtracted from the previous value. For example,
--debug=T
--debug=+P sets the value to
P:T.
For more information, see Section 7.9.4, “The DBUG Package”.
| Command-Line Format | --debug-sync-timeout[=#] |
|---|---|
| Type | Integer |
Controls whether the Debug Sync facility for testing and
debugging is enabled. Use of Debug Sync requires that MySQL be
configured with the
-DWITH_DEBUG=ON
CMake option (see
Section 2.8.7, “MySQL Source-Configuration Options”); otherwise,
this option is not available. The option value is a timeout in
seconds. The default value is 0, which disables Debug Sync. To
enable it, specify a value greater than 0; this value also
becomes the default timeout for individual synchronization
points. If the option is given without a value, the timeout is
set to 300 seconds.
For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.
| Command-Line Format | --default-time-zone=name |
|---|---|
| Type | String |
Set the default server time zone. This option sets the global
time_zone system variable. If
this option is not given, the default time zone is the same as
the system time zone (given by the value of the
system_time_zone system
variable.
The system_time_zone variable
differs from time_zone.
Although they might have the same value, the latter variable
is used to initialize the time zone for each client that
connects. See Section 7.1.15, “MySQL Server Time Zone Support”.
--defaults-extra-file=
file_name
Read this option file after the global option file but (on
Unix) before the user option file. If the file does not exist
or is otherwise inaccessible, an error occurs. If
file_name is not an absolute path
name, it is interpreted relative to the current directory.
This must be the first option on the command line if it is
used.
For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
Read only the given option file. If the file does not exist or
is otherwise inaccessible, an error occurs. If
file_name is not an absolute path
name, it is interpreted relative to the current directory.
Exception: Even with
--defaults-file,
mysqld reads
mysqld-auto.cnf.
This must be the first option on the command line if it is
used, except that if the server is started with the
--defaults-file and
--install (or
--install-manual) options,
--install (or
--install-manual) must be
first.
For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
Read not only the usual option groups, but also groups with
the usual names and a suffix of
str. For example,
mysqld normally reads the
[mysqld] group. If this option is given as
--defaults-group-suffix=_other,
mysqld also reads the
[mysqld_other] group.
For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
--early-plugin-load=
plugin_list
| Command-Line Format | --early-plugin-load=plugin_list |
|---|---|
| Type | String |
| Default Value | empty string |
This option tells the server which plugins to load before
loading mandatory built-in plugins and before storage engine
initialization. Early loading is supported only for plugins
compiled with PLUGIN_OPT_ALLOW_EARLY. If
multiple --early-plugin-load
options are given, only the last one applies.
The option value is a semicolon-separated list of
plugin_library and
name=plugin_library
values. Each plugin_library is the
name of a library file that contains plugin code, and each
name is the name of a plugin to
load. If a plugin library is named without any preceding
plugin name, the server loads all plugins in the library. With
a preceding plugin name, the server loads only the named
plugin from the library. The server looks for plugin library
files in the directory named by the
plugin_dir system variable.
For example, if plugins named myplug1 and
myplug2 are contained in the plugin library
files myplug1.so and
myplug2.so, use this option to perform an
early plugin load:
mysqld --early-plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
Quotes surround the argument value because otherwise some
command interpreters interpret semicolon
(;) as a special character. (For example,
Unix shells treat it as a command terminator.)
Each named plugin is loaded early for a single invocation of
mysqld only. After a restart, the plugin is
not loaded early unless
--early-plugin-load is used
again.
If the server is started using
--initialize or
--initialize-insecure, plugins
specified by
--early-plugin-load are not
loaded.
If the server is run with
--help, plugins specified by
--early-plugin-load are loaded
but not initialized. This behavior ensures that plugin options
are displayed in the help message.
InnoDB tablespace encryption relies on the
MySQL Keyring for encryption key management, and the keyring
plugin to be used must be loaded prior to storage engine
initialization to facilitate InnoDB
recovery for encrypted tables. For example, administrators who
want the keyring_okv plugin loaded at
startup should use
--early-plugin-load with the
appropriate option value (such as
keyring_okv.so on Unix and Unix-like
systems or keyring_okv.dll on Windows).
For information about InnoDB tablespace
encryption, see Section 17.13, “InnoDB Data-at-Rest Encryption”. For
general information about plugin loading, see
Section 7.6.1, “Installing and Uninstalling Plugins”.
For MySQL Keyring, this option is used only when the keystore is managed with a keyring plugin. If keystore management uses a keyring component rather than a plugin, specify component loading using a manifest file; see Section 8.4.4.2, “Keyring Component Installation”.
--exit-info[=,
flags]-T [
flags]
| Command-Line Format | --exit-info[=flags] |
|---|---|
| Type | Integer |
This is a bitmask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!
| Command-Line Format | --external-locking[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
Enable external locking (system locking), which is disabled by
default. If you use this option on a system on which
lockd does not fully work (such as Linux),
it is easy for mysqld to deadlock.
To disable external locking explicitly, use
--skip-external-locking.
External locking affects only
MyISAM table access. For more
information, including conditions under which it can and
cannot be used, see Section 10.11.5, “External Locking”.
| Command-Line Format | --flush[={OFF|ON}] |
|---|---|
| System Variable | flush |
| Scope | Global |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | Boolean |
| Default Value | OFF |
Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.3.3.3, “What to Do If MySQL Keeps Crashing”.
If --flush is specified, the
value of flush_time does
not matter and changes to
flush_time have no effect
on flush behavior.
| Command-Line Format | --gdb[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
Install an interrupt handler for SIGINT
(needed to stop mysqld with
^C to set breakpoints) and disable stack
tracing and core file handling. See
Section 7.9.1.4, “Debugging mysqld under gdb”.
On Windows, this option also suppresses the forking that is
used to implement the RESTART
statement: Forking enables one process to act as a monitor to
the other, which acts as the server. However, forking makes
determining the server process to attach to for debugging more
difficult, so starting the server with
--gdb suppresses forking. For a
server started with this option,
RESTART simply exits and does
not restart.
In non-debug settings,
--no-monitor may be used to
suppress forking the monitor process.
--initialize,
-I
| Command-Line Format | --initialize[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
This option is used to initialize a MySQL installation by
creating the data directory and populating the tables in the
mysql system schema. For more information,
see Section 2.9.1, “Initializing the Data Directory”.
This option limits the effects of, or is not compatible with, a number of other startup options for the MySQL server. Some of the most common issues of this sort are noted here:
We strongly recommend, when initializing the data
directory with --initialize, that you
specify no additional options other than
--datadir, other options
used for setting directory locations such as
--basedir, and possibly
--user, if required.
Options for the running MySQL server can be specified when
starting it once initialization has been completed and
mysqld has shut down. This also applies
when using
--initialize-insecure
instead of --initialize.
When the server is started with
--initialize, some functionality is
unavailable that limits the statements permitted in any
file named by the
init_file system
variable. For more information, see the description of
that variable. In addition, the
disabled_storage_engines
system variable has no effect.
The --ndbcluster option is
ignored when used together with
--initialize.
--initialize is mutually exclusive with
--bootstrap and
--daemonize.
The items in the preceding list also apply when initializing
the server using the
--initialize-insecure option.
| Command-Line Format | --initialize-insecure[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
This option is used to initialize a MySQL installation by
creating the data directory and populating the tables in the
mysql system schema. This option implies
--initialize, and the same
restrictions and limitations apply; for more information, see
the description of that option, and
Section 2.9.1, “Initializing the Data Directory”.
This option creates a MySQL root user
with an empty password, which is insecure. For this reason,
do not use it in production without setting this password
manually. See
Post-Initialization root Password Assignment,
for information about how to do this.
--innodb-
xxx
Set an option for the InnoDB storage
engine. The InnoDB options are listed in
Section 17.14, “InnoDB Startup Options and System Variables”.
| Command-Line Format | --install [service_name] |
|---|---|
| Platform Specific | Windows |
(Windows only) Install the server as a Windows service that
starts automatically during Windows startup. The default
service name is MySQL if no
service_name value is given. For
more information, see Section 2.3.3.8, “Starting MySQL as a Windows Service”.
If the server is started with the
--defaults-file and
--install options,
--install must be first.
--install-manual
[
service_name]
| Command-Line Format | --install-manual [service_name] |
|---|---|
| Platform Specific | Windows |
(Windows only) Install the server as a Windows service that
must be started manually. It does not start automatically
during Windows startup. The default service name is
MySQL if no
service_name value is given. For
more information, see Section 2.3.3.8, “Starting MySQL as a Windows Service”.
If the server is started with the
--defaults-file and
--install-manual options,
--install-manual must be
first.
| Command-Line Format | --large-pages[={OFF|ON}] |
|---|---|
| System Variable | large_pages |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Platform Specific | Linux |
| Type | Boolean |
| Default Value | OFF |
Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.
MySQL supports the Linux implementation of large page support
(which is called HugeTLB in Linux). See
Section 10.12.3.3, “Enabling Large Page Support”. For Solaris support of
large pages, see the description of the
--super-large-pages option.
--large-pages is disabled by
default.
| Command-Line Format | --lc-messages=name |
|---|---|
| System Variable | lc_messages |
| Scope | Global, Session |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | String |
| Default Value | en_US |
The locale to use for error messages. The default is
en_US. The server converts the argument to
a language name and combines it with the value of
--lc-messages-dir to produce
the location for the error message file. See
Section 12.12, “Setting the Error Message Language”.
| Command-Line Format | --lc-messages-dir=dir_name |
|---|---|
| System Variable | lc_messages_dir |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Directory name |
The directory where error messages are located. The server
uses the value together with the value of
--lc-messages to produce the
location for the error message file. See
Section 12.12, “Setting the Error Message Language”.
| Command-Line Format | --local-service |
|---|
(Windows only) A --local-service option
following the service name causes the server to run using the
LocalService Windows account that has
limited system privileges. If both
--defaults-file and
--local-service are given following the
service name, they can be in any order. See
Section 2.3.3.8, “Starting MySQL as a Windows Service”.
| Command-Line Format | --log-diagnostic[=file_name] |
|---|---|
| System Variable | log_diagnostic |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | File name |
Set the name of the diagnostic log file to this value suffixed
with .diag if the server is started with
--log-diagnostic-enable;
otherwise has no effect. The default diagnostic log file name
is
host_name.diag
For internal use only. Available only if the server was built
using -DWITH_LOG_DIAGNOSTIC.
--log-diagnostic-enable[=
value]
| Command-Line Format | --log-diagnostic-name[=true|false] |
|---|---|
| System Variable | log_diagnostic_enable |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Boolean |
| Default Value | false |
Enable diagnostic logging.
For internal use only. Available only if the server was built
using -DWITH_LOG_DIAGNOSTIC.
| Command-Line Format | --log-error[=file_name] |
|---|---|
| System Variable | log_error |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | File name |
Set the default error log destination to the named file. This affects log sinks that base their own output destination on the default destination. See Section 7.4.2, “The Error Log”.
If the option names no file, the default error log destination
on Unix and Unix-like systems is a file named
host_name.err--pid-file
option is specified. In that case, the file name is the PID
file base name with a suffix of .err in
the data directory.
If the option names a file, the default destination is that
file (with an .err suffix added if the
name has no suffix), located under the data directory unless
an absolute path name is given to specify a different
location.
If error log output cannot be redirected to the error log file, an error occurs and startup fails.
On Windows, --console takes
precedence over --log-error if
both are given. In this case, the default error log
destination is the console rather than a file.
| Command-Line Format | --log-isam[=file_name] |
|---|---|
| Type | File name |
Log all MyISAM changes to this file (used
only when debugging MyISAM).
| Command-Line Format | --log-raw[={OFF|ON}] |
|---|---|
| System Variable | log_raw |
| Scope | Global |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | Boolean |
| Default Value | OFF |
Passwords in certain statements written to the general query
log, slow query log, and binary log are rewritten by the
server not to occur literally in plain text. Password
rewriting can be suppressed for the general query log by
starting the server with the
--log-raw option. This option
may be useful for diagnostic purposes, to see the exact text
of statements as received by the server, but for security
reasons is not recommended for production use.
If a query rewrite plugin is installed, the
--log-raw option affects
statement logging as follows:
For more information, see Section 8.1.2.3, “Passwords and Logging”.
| 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.
| 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.
| Command-Line Format | --log-tc-size=# |
|---|---|
| Type | Integer |
| Default Value | 6 * page size |
| Minimum Value | 6 * page size |
| Maximum Value (64-bit platforms) | 18446744073709551615 |
| Maximum Value (32-bit platforms) | 4294967295 |
The size in bytes of the memory-mapped transaction coordinator log. The default and minimum values are 6 times the page size, and the value must be a multiple of the page size.
| Command-Line Format | --memlock[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.
--memlock works on systems that
support the mlockall() system call; this
includes Solaris, most Linux distributions that use a 2.4 or
higher kernel, and perhaps other Unix systems. On Linux
systems, you can tell whether or not
mlockall() (and thus this option) is
supported by checking to see whether or not it is defined in
the system mman.h file, like this:
$> grep mlockall /usr/include/sys/mman.h
If mlockall() is supported, you should see
in the output of the previous command something like the
following:
extern int mlockall (int __flags) __THROW;
Use of this option may require you to run the server as
root, which, for reasons of security, is
normally not a good idea. See
Section 8.1.5, “How to Run MySQL as a Normal User”.
On Linux and perhaps other systems, you can avoid the need
to run the server as root by changing the
limits.conf file. See the notes
regarding the memlock limit in
Section 10.12.3.3, “Enabling Large Page Support”.
You must not use this option on a system that does not
support the mlockall() system call; if
you do so, mysqld is very likely to exit
as soon as you try to start it.
| 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 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
| Command-Line Format | --no-monitor[={OFF|ON}] |
|---|---|
| Platform Specific | Windows |
| Type | Boolean |
| Default Value | OFF |
(Windows only). This option suppresses the forking that is
used to implement the RESTART
statement: Forking enables one process to act as a monitor to
the other, which acts as the server. For a server started with
this option, RESTART simply
exits and does not restart.
--performance-schema-xxx
Configure a Performance Schema option. For details, see Section 29.14, “Performance Schema Command Options”.
| Command-Line Format | --plugin-load=plugin_list |
|---|---|
| Type | String |
This option tells the server to load the named plugins at
startup. If multiple
--plugin-load options are
given, only the last one applies. Additional plugins to load
may be specified using
--plugin-load-add options.
The option value is a semicolon-separated list of
plugin_library and
name=plugin_library
values. Each plugin_library is the
name of a library file that contains plugin code, and each
name is the name of a plugin to
load. If a plugin library is named without any preceding
plugin name, the server loads all plugins in the library. With
a preceding plugin name, the server loads only the named
plugin from the library. The server looks for plugin library
files in the directory named by the
plugin_dir system variable.
For example, if plugins named myplug1 and
myplug2 are contained in the plugin library
files myplug1.so and
myplug2.so, use this option to perform an
early plugin load:
mysqld --plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
Quotes surround the argument value because otherwise some
command interpreters interpret semicolon
(;) as a special character. (For example,
Unix shells treat it as a command terminator.)
Each named plugin is loaded for a single invocation of
mysqld only. After a restart, the plugin is
not loaded unless --plugin-load
is used again. This is in contrast to
INSTALL PLUGIN, which adds an
entry to the mysql.plugins table to cause
the plugin to be loaded for every normal server startup.
During the normal startup sequence, the server determines
which plugins to load by reading the
mysql.plugins system table. If the server
is started with the
--skip-grant-tables option,
plugins registered in the mysql.plugins
table are not loaded and are unavailable.
--plugin-load enables plugins
to be loaded even when
--skip-grant-tables is given.
--plugin-load also enables
plugins to be loaded at startup that cannot be loaded at
runtime.
This option does not set a corresponding system variable. The
output of SHOW PLUGINS provides
information about loaded plugins. More detailed information
can be found in the Information Schema
PLUGINS table. See
Section 7.6.2, “Obtaining Server Plugin Information”.
For additional information about plugin loading, see Section 7.6.1, “Installing and Uninstalling Plugins”.
| Command-Line Format | --plugin-load-add=plugin_list |
|---|---|
| Type | String |
This option complements the
--plugin-load option.
--plugin-load-add adds a plugin
or plugins to the set of plugins to be loaded at startup. The
argument format is the same as for
--plugin-load.
--plugin-load-add can be used
to avoid specifying a large set of plugins as a single long
unwieldy --plugin-load
argument.
--plugin-load-add can be given
in the absence of
--plugin-load, but any instance
of --plugin-load-add that
appears before --plugin-load.
has no effect because
--plugin-load resets the set of
plugins to load. In other words, these options:
--plugin-load=x --plugin-load-add=y
are equivalent to this option:
--plugin-load="x;y"
But these options:
--plugin-load-add=y --plugin-load=x
are equivalent to this option:
--plugin-load=x
This option does not set a corresponding system variable. The
output of SHOW PLUGINS provides
information about loaded plugins. More detailed information
can be found in the Information Schema
PLUGINS table. See
Section 7.6.2, “Obtaining Server Plugin Information”.
For additional information about plugin loading, see Section 7.6.1, “Installing and Uninstalling Plugins”.
Specifies an option that pertains to a server plugin. For
example, many storage engines can be built as plugins, and for
such engines, options for them can be specified with a
--plugin prefix. Thus, the
--innodb-file-per-table option
for InnoDB can be specified as
--plugin-innodb-file-per-table.
For boolean options that can be enabled or disabled, the
--skip prefix and other alternative formats
are supported as well (see
Section 6.2.2.4, “Program Option Modifiers”). For example,
--skip-plugin-innodb-file-per-table
disables innodb-file-per-table.
The rationale for the --plugin prefix is that
it enables plugin options to be specified unambiguously if
there is a name conflict with a built-in server option. For
example, were a plugin writer to name a plugin
“sql” and implement a “mode” option,
the option name might be
--sql-mode, which would
conflict with the built-in option of the same name. In such
cases, references to the conflicting name are resolved in
favor of the built-in option. To avoid the ambiguity, users
can specify the plugin option as
--plugin-sql-mode. Use of the
--plugin prefix for plugin options is
recommended to avoid any question of ambiguity.
--port=,
port_num-P
port_num
| Command-Line Format | --port=port_num |
|---|---|
| System Variable | port |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Integer |
| Default Value | 3306 |
| Minimum Value | 0 |
| Maximum Value | 65535 |
The port number to use when listening for TCP/IP connections.
On Unix and Unix-like systems, the port number must be 1024 or
higher unless the server is started by the
root operating system user. Setting this
option to 0 causes the default value to be used.
| Command-Line Format | --port-open-timeout=# |
|---|---|
| Type | Integer |
| Default Value | 0 |
On some systems, when the server is stopped, the TCP/IP port might not become available immediately. If the server is restarted quickly afterward, its attempt to reopen the port can fail. This option indicates how many seconds the server should wait for the TCP/IP port to become free if it cannot be opened. The default is not to wait.
Print the program name and all options that it gets from
option files. Password values are masked. This must be the
first option on the command line if it is used, except that it
may be used immediately after
--defaults-file or
--defaults-extra-file.
For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
| Command-Line Format | --remove [service_name] |
|---|---|
| Platform Specific | Windows |
(Windows only) Remove a MySQL Windows service. The default
service name is MySQL if no
service_name value is given. For
more information, see Section 2.3.3.8, “Starting MySQL as a Windows Service”.
| Command-Line Format | --safe-user-create[={OFF|ON}] |
|---|---|
| Deprecated | Yes |
| Type | Boolean |
| Default Value | OFF |
If this option is enabled, a user cannot create new MySQL
users by using the GRANT
statement unless the user has the
INSERT privilege for the
mysql.user system table or any column in
the table. If you want a user to have the ability to create
new users that have those privileges that the user has the
right to grant, you should grant the user the following
privilege:
GRANT INSERT(user) ON mysql.user TO 'user_name'@'host_name';
This ensures that the user cannot change any privilege columns
directly, but has to use the
GRANT statement to give
privileges to other users.
| Command-Line Format | --skip-grant-tables[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
This option affects the server startup sequence:
--skip-grant-tables causes
the server not to read the grant tables in the
mysql system schema, and thus to start
without using the privilege system at all. This gives
anyone with access to the server unrestricted
access to all databases.
Because starting the server with
--skip-grant-tables
disables authentication checks, the server also disables
remote connections in that case by enabling
skip_networking.
To cause a server started with
--skip-grant-tables to load
the grant tables at runtime, perform a privilege-flushing
operation, which can be done in these ways:
Issue a MySQL FLUSH
PRIVILEGES statement after connecting to the
server.
Execute a mysqladmin flush-privileges or mysqladmin reload command from the command line.
Privilege flushing might also occur implicitly as a result of other actions performed after startup, thus causing the server to start using the grant tables. For example, the server flushes the privileges if it performs an upgrade during the startup sequence.
--skip-grant-tables
disables failed-login tracking and temporary account
locking because those capabilities depend on the grant
tables. See Section 8.2.15, “Password Management”.
--skip-grant-tables causes
the server not to load certain other objects registered in
the data dictionary or the mysql system
schema:
Scheduled events installed using
CREATE EVENT and
registered in the events data
dictionary table.
Plugins installed using INSTALL
PLUGIN and registered in the
mysql.plugin system table.
To cause plugins to be loaded even when using
--skip-grant-tables,
use the --plugin-load
or --plugin-load-add
option.
Loadable functions installed using
CREATE
FUNCTION and registered in the
mysql.func system table.
--skip-grant-tables does
not suppress loading during startup
of components.
--skip-grant-tables causes
the
disabled_storage_engines
system variable to have no effect.
| Command-Line Format | --skip-new |
|---|---|
| Deprecated | Yes |
This option disables (what used to be considered) new,
possibly unsafe behaviors. It results in these settings:
delay_key_write=OFF,
concurrent_insert=NEVER,
automatic_sp_privileges=OFF.
It also causes OPTIMIZE TABLE
to be mapped to ALTER TABLE for
storage engines for which OPTIMIZE
TABLE is not supported.
This option is deprecated, and subject to removal in a future release.
| Command-Line Format | --skip-show-database |
|---|---|
| System Variable | skip_show_database |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Boolean |
| Default Value | OFF |
This option sets the
skip_show_database system
variable that controls who is permitted to use the
SHOW DATABASES statement. See
Section 7.1.8, “Server System Variables”.
| Command-Line Format | --skip-stack-trace |
|---|
Do not write stack traces. This option is useful when you are running mysqld under a debugger. On some systems, you also must use this option to get a core file. See Section 7.9, “Debugging MySQL”.
| Command-Line Format | --slow-start-timeout=# |
|---|---|
| Type | Integer |
| Default Value | 15000 |
This option controls the Windows service control manager's service start timeout. The value is the maximum number of milliseconds that the service control manager waits before trying to kill the windows service during startup. The default value is 15000 (15 seconds). If the MySQL service takes too long to start, you may need to increase this value. A value of 0 means there is no timeout.
| Command-Line Format | --socket={file_name|pipe_name} |
|---|---|
| System Variable | socket |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | String |
| Default Value (Windows) | MySQL |
| Default Value (Other) | /tmp/mysql.sock |
On Unix, this option specifies the Unix socket file to use
when listening for local connections. The default value is
/tmp/mysql.sock. If this option is given,
the server creates the file in the data directory unless an
absolute path name is given to specify a different directory.
On Windows, the option specifies the pipe name to use when
listening for local connections that use a named pipe. The
default value is MySQL (not
case-sensitive).
--sql-mode=
value[,value[,value...]]
| Command-Line Format | --sql-mode=name |
|---|---|
| System Variable | sql_mode |
| Scope | Global, Session |
| Dynamic | Yes |
SET_VAR Hint Applies |
Yes |
| Type | Set |
| Default Value | ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_ZERO_IN_DATE NO_ZERO_DATE ERROR_FOR_DIVISION_BY_ZERO NO_ENGINE_SUBSTITUTION |
| Valid Values |
|
Set the SQL mode. See Section 7.1.11, “Server SQL Modes”.
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.
| Command-Line Format | --standalone |
|---|---|
| Platform Specific | Windows |
Available on Windows only; instructs the MySQL server not to run as a service.
| Command-Line Format | --super-large-pages[={OFF|ON}] |
|---|---|
| Platform Specific | Solaris |
| Type | Boolean |
| Default Value | OFF |
Standard use of large pages in MySQL attempts to use the
largest size supported, up to 4MB. Under Solaris, a
“super large pages” feature enables uses of pages
up to 256MB. This feature is available for recent SPARC
platforms. It can be enabled or disabled by using the
--super-large-pages or
--skip-super-large-pages
option.
--symbolic-links,
--skip-symbolic-links
| Command-Line Format | --symbolic-links[={OFF|ON}] |
|---|---|
| Deprecated | Yes |
| Type | Boolean |
| Default Value | OFF |
Enable or disable symbolic link support. On Unix, enabling
symbolic links means that you can link a
MyISAM index file or data file to another
directory with the INDEX DIRECTORY or
DATA DIRECTORY option of the
CREATE TABLE statement. If you
delete or rename the table, the files that its symbolic links
point to also are deleted or renamed. See
Section 10.12.2.2, “Using Symbolic Links for MyISAM Tables on Unix”.
Symbolic link support, along with the
--symbolic-links option that
controls it, is deprecated; you should expect it to be
removed in a future version of MySQL. In addition, the
option is disabled by default. The related
have_symlink system
variable also is deprecated; expect it to be removed in a
future version of MySQL.
This option has no meaning on Windows.
| Command-Line Format | --sysdate-is-now[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
SYSDATE() by default returns
the time at which it executes, not the time at which the
statement in which it occurs begins executing. This differs
from the behavior of NOW().
This option causes SYSDATE() to
be a synonym for NOW(). For
information about the implications for binary logging and
replication, see the description for
SYSDATE() in
Section 14.7, “Date and Time Functions” and for SET
TIMESTAMP in
Section 7.1.8, “Server System Variables”.
--tc-heuristic-recover={COMMIT|ROLLBACK}
| Command-Line Format | --tc-heuristic-recover=name |
|---|---|
| Type | Enumeration |
| Default Value | OFF |
| Valid Values |
|
The decision to use in a manual heuristic recovery.
If a --tc-heuristic-recover option is
specified, the server exits regardless of whether manual
heuristic recovery is successful.
On systems with more than one storage engine capable of
two-phase commit, the ROLLBACK option is
not safe and causes recovery to halt with the following error:
[ERROR] --tc-heuristic-recover rollback strategy is not safe on systems with more than one 2-phase-commit-capable storage engine. Aborting crash recovery.
| Command-Line Format | --transaction-isolation=name |
|---|---|
| System Variable | transaction_isolation |
| Scope | Global, Session |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | Enumeration |
| Default Value | REPEATABLE-READ |
| Valid Values |
|
Sets the default transaction isolation level. The
level value can be
READ-UNCOMMITTED,
READ-COMMITTED,
REPEATABLE-READ, or
SERIALIZABLE. See
Section 15.3.7, “SET TRANSACTION Statement”.
The default transaction isolation level can also be set at
runtime using the SET
TRANSACTION statement or by setting the
transaction_isolation system
variable.
| Command-Line Format | --transaction-read-only[={OFF|ON}] |
|---|---|
| System Variable | transaction_read_only |
| Scope | Global, Session |
| Dynamic | Yes |
SET_VAR Hint Applies |
No |
| Type | Boolean |
| Default Value | OFF |
Sets the default transaction access mode. By default, read-only mode is disabled, so the mode is read/write.
To set the default transaction access mode at runtime, use the
SET TRANSACTION statement or
set the transaction_read_only
system variable. See Section 15.3.7, “SET TRANSACTION Statement”.
--tmpdir=,
dir_name-t
dir_name
| Command-Line Format | --tmpdir=dir_name |
|---|---|
| System Variable | tmpdir |
| Scope | Global |
| Dynamic | No |
SET_VAR Hint Applies |
No |
| Type | Directory name |
The path of the directory to use for creating temporary files.
It might be useful if your default /tmp
directory resides on a partition that is too small to hold
temporary tables. This option accepts several paths that are
used in round-robin fashion. Paths should be separated by
colon characters (:) on Unix and semicolon
characters (;) on Windows.
--tmpdir can be a non-permanent
location, such as a directory on a memory-based file system or
a directory that is cleared when the server host restarts. If
the MySQL server is acting as a replica, and you are using a
non-permanent location for
--tmpdir, consider setting a
different temporary directory for the replica using the
replica_load_tmpdir system
variable. For a replica, the temporary files used to replicate
LOAD DATA statements are stored
in this directory, so with a permanent location they can
survive machine restarts, although replication can now
continue after a restart if the temporary files have been
removed.
For more information about the storage location of temporary files, see Section B.3.3.5, “Where MySQL Stores Temporary Files”.
| Command-Line Format | --upgrade=value |
|---|---|
| Type | Enumeration |
| Default Value | AUTO |
| Valid Values |
|
This option controls whether and how the server performs an automatic upgrade at startup. Automatic upgrade involves two steps:
Step 1: Data dictionary upgrade.
This step upgrades:
The data dictionary tables in the
mysql schema. If the actual data
dictionary version is lower than the current expected
version, the server upgrades the data dictionary. If
it cannot, or is prevented from doing so, the server
cannot run.
The Performance Schema and
INFORMATION_SCHEMA.
Step 2: Server upgrade.
This step comprises all other upgrade tasks. If the existing installation data has a lower MySQL version than the server expects, it must be upgraded:
The system tables in the mysql
schema (the remaining non-data dictionary tables).
The sys schema.
User schemas.
For details about upgrade steps 1 and 2, see Section 3.4, “What the MySQL Upgrade Process Upgrades”.
These --upgrade option values
are permitted:
AUTO
The server performs an automatic upgrade of anything it
finds to be out of date (steps 1 and 2). This is the
default action if --upgrade
is not specified explicitly.
NONE
The server performs no automatic upgrade steps during the startup process (skips steps 1 and 2). Because this option value prevents a data dictionary upgrade, the server exits with an error if the data dictionary is found to be out of date:
[ERROR] [MY-013381] [Server] Server shutting down because upgrade is required, yet prohibited by the command line option '--upgrade=NONE'. [ERROR] [MY-010334] [Server] Failed to initialize DD Storage Engine [ERROR] [MY-010020] [Server] Data Dictionary initialization failed.
MINIMAL
The server upgrades the data dictionary, the Performance
Schema, and the INFORMATION_SCHEMA, if
necessary (step 1). Note that following an upgrade with
this option, Group Replication cannot be started, because
system tables on which the replication internals depend
are not updated, and reduced functionality might also be
apparent in other areas.
FORCE
The server upgrades the data dictionary, the Performance
Schema, and the INFORMATION_SCHEMA, if
necessary (step 1). In addition, the server forces an
upgrade of everything else (step 2). Expect server startup
to take longer with this option because the server checks
all objects in all schemas.
FORCE is useful to force step 2 actions
to be performed if the server thinks they are not
necessary. For example, you may believe that a system
table is missing or has become damaged and want to force a
repair.
The following table summarizes the actions taken by the server for each option value.
| Option Value | Server Performs Step 1? | Server Performs Step 2? |
|---|---|---|
AUTO |
If necessary | If necessary |
NONE |
No | No |
MINIMAL |
If necessary | No |
FORCE |
If necessary | Yes |
--user={,
user_name|user_id}-u
{
user_name|user_id}
| Command-Line Format | --user=name |
|---|---|
| Type | String |
Run the mysqld server as the user having
the name user_name or the numeric
user ID user_id.
(“User” in this context refers to a system login
account, not a MySQL user listed in the grant tables.)
This option is mandatory when starting
mysqld as root. The
server changes its user ID during its startup sequence,
causing it to run as that particular user rather than as
root. See
Section 8.1.1, “Security Guidelines”.
To avoid a possible security hole where a user adds a
--user=root option to a
my.cnf file (thus causing the server to
run as root), mysqld
uses only the first --user
option specified and produces a warning if there are multiple
--user options. Options in
/etc/my.cnf and
$MYSQL_HOME/my.cnf are processed before
command-line options, so it is recommended that you put a
--user option in
/etc/my.cnf and specify a value other
than root. The option in
/etc/my.cnf is found before any other
--user options, which ensures
that the server runs as a user other than
root, and that a warning results if any
other --user option is found.
| Command-Line Format | --validate-config[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | OFF |
Validate the server startup configuration. If no errors are
found, the server terminates with an exit code of 0. If an
error is found, the server displays a diagnostic message and
terminates with an exit code of 1. Warning and information
messages may also be displayed, depending on the
log_error_verbosity value,
but do not produce immediate validation termination or an exit
code of 1. For more information, see
Section 7.1.3, “Server Configuration Validation”.
--validate-user-plugins[={OFF|ON}]
| Command-Line Format | --validate-user-plugins[={OFF|ON}] |
|---|---|
| Type | Boolean |
| Default Value | ON |
If this option is enabled (the default), the server checks each user account and produces a warning if conditions are found that would make the account unusable:
The account requires an authentication plugin that is not loaded.
The account requires the
sha256_password (deprecated) or
caching_sha2_password authentication
plugin but the server was started with neither SSL nor RSA
enabled as required by the plugin.
Enabling
--validate-user-plugins slows
down server initialization and FLUSH
PRIVILEGES. If you do not require the additional
checking, you can disable this option at startup to avoid the
performance decrement.
Use this option with the --help
option for detailed help.
--version, -V
Display version information and exit.