MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
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 17.1.4, “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 14.14, “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--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.
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 |
This option is used by the mysql_install_db program to create the MySQL privilege tables without having to start a full MySQL server.
Replication and global transaction identifiers are automatically disabled whenever this option is used (Bug #13992602). See Section 17.1.3, “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.
--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 limits LOAD
DATA and
SELECT ... INTO
OUTFILE.
| Property | Value |
|---|---|
| Command-Line Format | --console |
| Platform Specific | Windows |
(Windows only.) Write error log messages to
stderr and stdout (the
console). mysqld does not close the console
window if this option is used.
--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.
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 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
| 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
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 24.5.3, “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.
--default-authentication-plugin=
plugin_name
| Property | Value |
|---|---|
| Command-Line Format | --default-authentication-plugin=plugin_name |
| Type | Enumeration |
| Default Value | mysql_native_password |
| Valid Values |
|
This option sets the default authentication plugin. These values are permitted:
mysql_native_password: Use MySQL native
passwords; see
Section 6.4.1.1, “Native Pluggable Authentication”.
sha256_password: Use SHA-256 passwords;
see Section 6.4.1.4, “SHA-256 Pluggable Authentication”.
Prior to MySQL 5.6.17, if you use this option to change the
default authentication plugin to a value other than
mysql_native_password, clients older than
MySQL 5.5.7 cannot connect because they do not understand
the resulting change to the authentication protocol.
In MySQL 5.6, there is no server system variable
that corresponds to the
--default-authentication-plugin
option; to read the value set for this option, you
must check the running MySQL Server process to see what
options, if any, were employed when invoking
mysqld (on Linux systems, you can do this
with ps ax | grep mysqld or similar), and
possibly the server options file as well. This is a known
issue which is resolved in MySQL 5.7. (Bug #68858, Bug
#16595944)
The
--default-authentication-plugin
value affects these aspects of server operation:
It determines which authentication plugin the server
assigns to new accounts created by
CREATE USER and
GRANT statements that do
not explicitly specify an authentication plugin.
The old_passwords system
variable affects password hashing for accounts that use
the mysql_native_password or
sha256_password authentication plugin.
If the default authentication plugin is one of those
plugins, the server sets
old_passwords at startup
to the value required by the plugin password hashing
method.
For an account created with either of the following statements, the server associates the account with the default authentication plugin and assigns the account the given password, hashed as required by that plugin:
CREATE USER ... IDENTIFIED BY 'cleartext password'; GRANT ... IDENTIFIED BY 'cleartext password';
For an account created with either of the following statements, the server associates the account with the default authentication plugin and assigns the account the given password hash, if the password hash has the format required by the plugin:
CREATE USER ... IDENTIFIED BY PASSWORD 'encrypted password'; GRANT ... IDENTIFIED BY PASSWORD 'encrypted password';
If the password hash is not in the format required by the default authentication plugin, the statement fails.
| 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 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. 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.
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 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 |
Read the default DES keys from this file. These keys are used
by the DES_ENCRYPT() and
DES_DECRYPT() functions.
--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”.
If --flush is specified, the
value of flush_time does
not matter and changes to
flush_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 24.5.1.4, “Debugging mysqld under gdb”.
| Property | Value |
|---|---|
| Command-Line Format | --ignore-db-dir=dir_name |
| Type | Directory name |
This option tells the server to ignore the given directory
name for purposes of the SHOW
DATABASES statement or
INFORMATION_SCHEMA tables. For example, if
a MySQL configuration locates the data directory at the root
of a file system on Unix, the system might create a
lost+found directory there that the
server should ignore. Starting the server with
--ignore-db-dir=lost+found
causes that name not to be listed as a database.
To specify more than one name, use this option multiple times,
once for each name. Specifying the option with an empty value
(that is, as --ignore-db-dir=)
resets the directory list to the empty list.
Instances of this option given at server startup are used to
set the ignore_db_dirs system
variable.
--innodb-
xxx
Set an option for the InnoDB storage
engine. The InnoDB options are listed in
Section 14.14, “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 no
service_name value is given. For
more information, see Section 2.3.4.7, “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]
| 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 no
service_name value is given. For
more information, see Section 2.3.4.7, “Starting MySQL as a Windows Service”.
If the server is started with the
--defaults-file and
--install-manual options,
--install-manual must be
first.
--language=
lang_name,
-L lang_name
| Property | Value |
|---|---|
| Command-Line Format | --language=name |
| Deprecated | Yes; use lc-messages-dir instead |
| System 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 an alias 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 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 2.3.4.7, “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
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 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, --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 debugging MyISAM).
| 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.
| 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-slow-admin-statements[={OFF|ON}] (5.6.10) |
| Removed | 5.6.11 |
| Type | Boolean |
| Default Value | OFF |
Include slow administrative statements in the statements
written to the slow query log. Administrative statements
include ALTER TABLE,
ANALYZE TABLE,
CHECK TABLE,
CREATE INDEX,
DROP INDEX,
OPTIMIZE TABLE, and
REPAIR TABLE.
This command-line option was removed in MySQL 5.6.11 and
replaced by the
log_slow_admin_statements
system variable. The system variable can be set on the command
line or in option files the same way as the option, so there
is no need for any changes at server startup, but the system
variable also makes it possible to examine or set the value at
runtime.
| 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 | 24576 |
| 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 size is 24KB.
--log-warnings[=,
level]-W [
level]
| Property | Value |
|---|---|
| Command-Line Format | --log-warnings[=#] |
| System Variable | log_warnings |
| Scope | Global |
| Dynamic | Yes |
| Type | Integer |
| Default Value | 1 |
| Minimum Value | 0 |
| Maximum Value (64-bit platforms) | 18446744073709551615 |
| Maximum Value (32-bit platforms) | 4294967295 |
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, and access-denied
errors for new connection attempts are written. See
Section B.4.2.11, “Communication Errors and Aborted Connections”.
If a slave server was started with
--log-warnings enabled, the
slave prints messages to the error log to provide information
about its status, such as the binary log and relay log
coordinates where it starts its job, when it is switching to
another relay log, when it reconnects after a disconnect, and
so forth. The server logs messages about statements that are
unsafe for statement-based logging if
--log-warnings is greater than
0.
| 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 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:
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;
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 8.12.4.2, “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 6.2.13, “Setting Account Resource Limits”.
| Property | Value |
|---|---|
| Command-Line Format | --partition[={OFF|ON}] |
| Disabled by | skip-partition |
| Type | Boolean |
| Default Value | ON |
Enables or disables user-defined partitioning support in the MySQL Server.
--performance-schema-xxx
Configure a Performance Schema option. For details, see Section 22.14, “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
and plugin_library values. Each
name is the name of a plugin to
load, and plugin_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 the
plugin_dir system variable.
For example, if plugins named myplug1 and
myplug2 have library files
myplug1.so and
myplug2.so, use this option to 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 to
INSTALL PLUGIN, which adds an
entry to the mysql.plugins table to cause
the plugin to be loaded for every normal server startup.
Under normal startup, the server determines which plugins to
load by reading the mysql.plugins system
table. If the server is started with the
--skip-grant-tables option, it
does not consult the mysql.plugins table
and does not load plugins listed there.
--plugin-load enables plugins
to be loaded even when
--skip-grant-tables is given.
--plugin-load also enables
plugins to be loaded at startup 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
for InnoDB can be specified as
--plugin-innodb-file-per-table.
For boolean options that can be enabled or disabled, the
--skip prefix and other alternative formats
are supported as well (see
Section 4.2.2.4, “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
| Property | Value |
|---|---|
| Command-Line Format | --port=port_num |
| System Variable | port |
| Scope | Global |
| Dynamic | 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.
| Property | Value |
|---|---|
| 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. 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 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.
| Property | Value |
|---|---|
| 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 2.3.4.7, “Starting MySQL as a Windows Service”.
| Property | Value |
|---|---|
| Command-Line Format | --safe-user-create[={OFF|ON}] |
| 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.
| Property | Value |
|---|---|
| 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 database, and thus to
start without using the privilege system at all. This
gives anyone with access to the server
unrestricted access to all databases.
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, mysql_upgrade flushes the privileges during the upgrade procedure.
In addition to causing the startup sequence not to load
the grant tables,
--skip-grant-tables causes
the server not to load certain other objects stored in the
mysql system database: plugins that
were installed with the INSTALL
PLUGIN statement, scheduled events, and
user-defined functions (UDFs). To cause plugins to be
loaded anyway, use the
--plugin-load or
--plugin-load-add option.
| Property | Value |
|---|---|
| Command-Line Format | --skip-host-cache |
Disable use of the internal host cache for faster name-to-IP resolution. With the cache disabled, the server performs a DNS lookup every time a client connects.
Use of --skip-host-cache is
similar to setting the
host_cache_size system
variable to 0, but
host_cache_size is more
flexible because it can also be used to resize, enable, or
disable the host cache at runtime, not just at server startup.
If you start the server with
--skip-host-cache, that does
not prevent changes to the value of
host_cache_size, but such
changes have no effect and the cache is not re-enabled even if
host_cache_size is set larger
than 0.
For more information about how the host cache works, see Section 5.1.11.2, “DNS Lookups and the Host Cache”.
Disable the InnoDB storage engine. In this
case, because the default storage engine is
InnoDB, the server will not start
unless you also use
--default-storage-engine and
--default-tmp-storage-engine to
set the default to some other engine for both permanent and
TEMPORARY tables.
As of MySQL 5.6.21, the
--skip-innodb
option is deprecated. Its use results in a warning. This
option will be removed in a future MySQL release.
| Property | Value |
|---|---|
| Command-Line Format | --skip-new |
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.
| Property | Value |
|---|---|
| Command-Line Format |
|
Disables user-defined partitioning. Partitioned tables can be
seen using SHOW TABLES or by
querying the
INFORMATION_SCHEMA.TABLES table,
but cannot be created or modified, nor can data in such tables
be accessed. All partition-specific columns in the
INFORMATION_SCHEMA.PARTITIONS
table display NULL.
Since DROP TABLE removes table
definition (.frm) files, this statement
works on partitioned tables even when partitioning is disabled
using the option. The statement, however, does not remove
.par files associated with partitioned
tables in such cases. For this reason, you should avoid
dropping partitioned tables with partitioning disabled, or
take action to remove the orphaned .par
files manually.
| Property | Value |
|---|---|
| Command-Line Format | --skip-show-database |
| System Variable | skip_show_database |
| Scope | Global |
| Dynamic | No |
This option sets the
skip_show_database system
variable that controls who is permitted to use the
SHOW DATABASES statement. See
Section 5.1.7, “Server System Variables”.
| Property | Value |
|---|---|
| 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 24.5, “Debugging and Porting MySQL”.
| Property | Value |
|---|---|
| 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.
| Property | Value |
|---|---|
| Command-Line Format | --socket={file_name|pipe_name} |
| System Variable | socket |
| Scope | Global |
| Dynamic | No |
| Type | String |
| Default Value (Other) | /tmp/mysql.sock |
| Default Value (Windows) | MySQL |
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...]]
| Property | Value |
|---|---|
| Command-Line Format | --sql-mode=name |
| System Variable | sql_mode |
| Scope | Global, Session |
| Dynamic | Yes |
| Type | Set |
| Default Value | NO_ENGINE_SUBSTITUTION |
| Valid Values |
|
Set the SQL mode. The default is
NO_ENGINE_SUBSTITUTION. See
Section 5.1.10, “Server SQL Modes”.
MySQL installation programs may configure the SQL mode
during the installation process. For example,
mysql_install_db creates a default option
file named my.cnf in the base
installation directory. This file contains a line that sets
the SQL mode; see Section 4.4.3, “mysql_install_db — Initialize MySQL Data Directory”.
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.
| Property | Value |
|---|---|
| Command-Line Format | --ssl[={OFF|ON}] |
| Disabled by | skip-ssl |
| Type | Boolean |
| Default Value | OFF |
This option specifies that the server permits but does not
require encrypted connections.
--ssl may be implied by setting
ssl_ system
variables, as indicated in the descriptions for those
variables.
xxx
--ssl can be specified in
negated form as
--skip-ssl or a
synonym (--ssl=OFF,
--disable-ssl).
In this case, the option specifies that the server does
not permit encrypted connections,
regardless of the settings of the
ssl_ system
variables.
xxx
For more information about configuring whether the server
permits clients to connect using SSL and indicating where to
find SSL keys and certificates, see
Section 6.3.1, “Configuring MySQL to Use Encrypted Connections”. Consider
setting at least the ssl_cert
and ssl_key system variables
on the server side and the
--ssl-ca (or
--ssl-capath) option on the
client side.
| Property | Value |
|---|---|
| Command-Line Format | --standalone |
| Platform Specific | Windows |
Available on Windows only; instructs the MySQL server not to run as a service.
| Property | Value |
|---|---|
| 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
| Property | Value |
|---|---|
| Command-Line Format | --symbolic-links[={OFF|ON}] |
| Type | Boolean |
| Default Value | ON |
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
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 8.12.3.2, “Using Symbolic Links for MyISAM Tables on Unix”.
| Property | Value |
|---|---|
| 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 an alias for NOW(). For
information about the implications for binary logging and
replication, see the description for
SYSDATE() in
Section 12.6, “Date and Time Functions” and for SET
TIMESTAMP in
Section 5.1.7, “Server System Variables”.
--tc-heuristic-recover={COMMIT|ROLLBACK}
| Property | Value |
|---|---|
| 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.
| Property | Value |
|---|---|
| Command-Line Format | --temp-pool[={OFF|ON}] |
| Type | Boolean |
| Default Value (Other) | OFF |
| Default Value (Linux) | ON |
This option is ignored except on Linux. On Linux, it 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.
| Property | Value |
|---|---|
| Command-Line Format | --transaction-isolation=name |
| 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 13.3.6, “SET TRANSACTION Statement”.
The default transaction isolation level can also be set at
runtime using the SET
TRANSACTION statement or by setting the
tx_isolation system variable.
| Property | Value |
|---|---|
| Command-Line Format | --transaction-read-only[={OFF|ON}] |
| 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 tx_read_only system
variable. See Section 13.3.6, “SET TRANSACTION Statement”.
--tmpdir=,
dir_name-t
dir_name
| Property | Value |
|---|---|
| Command-Line Format | --tmpdir=dir_name |
| System Variable | tmpdir |
| Scope | Global |
| Dynamic | 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 replication slave, and you are
using a non-permanent location for
--tmpdir, consider setting a
different temporary directory for the slave using the
slave_load_tmpdir system
variable. For a replication slave, 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.4.3.5, “Where MySQL Stores Temporary Files”.
--user={,
user_name|user_id}-u
{
user_name|user_id}
| Property | Value |
|---|---|
| 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 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.
Use this option with the --help
option for detailed help.
--version, -V
Display version information and exit.