MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.2, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 4.2.2.2, “Using Option Files”. That section also describes option file format and syntax.
mysqld reads options from the
[mysqld]
and [server]
groups. mysqld_safe reads options from the
[mysqld]
, [server]
,
[mysqld_safe]
, and
[safe_mysqld]
groups.
mysql.server reads options from the
[mysqld]
and [mysql.server]
groups.
An embedded MySQL server usually reads options from the
[server]
, [embedded]
, and
[
groups, where xxxxx
_SERVER]xxxxx
is the name of the
application into which the server is embedded.
mysqld accepts many command options. For a brief summary, execute this command:
mysqld --help
To see the full list, use this command:
mysqld --verbose --help
Some of the items in the list are actually system variables that
can be set at server startup. These can be displayed at runtime
using the SHOW VARIABLES
statement.
Some items displayed by the preceding mysqld
command do not appear in SHOW
VARIABLES
output; this is because they are options only
and not system variables.
The following list shows some of the most common server options. Additional options are described in other sections:
Options that affect security: See Section 6.1.4, “Security-Related mysqld Options and Variables”.
SSL-related options: See Command Options for Encrypted Connections.
Binary log control options: See Section 5.4.4, “The Binary Log”.
Replication-related options: See Section 16.1.6, “Replication and Binary Logging Options and Variables”.
Options for loading plugins such as pluggable storage engines: See Section 5.5.1, “Installing and Uninstalling Plugins”.
Options specific to particular storage engines: See Section 14.15, “InnoDB Startup Options and System Variables” and Section 15.2.1, “MyISAM Startup Options”.
Some options control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to an option that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server will set the value to 1024.
Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.
Some options take file name values. Unless otherwise specified,
the default file location is the data directory if the value is a
relative path name. To specify the location explicitly, use an
absolute path name. Suppose that the data directory is
/var/mysql/data
. If a file-valued option is
given as a relative path name, it will be located under
/var/mysql/data
. If the value is an absolute
path name, its location is as given by the path name.
You can also set the values of server system variables at server
startup by using variable names as options. To assign a value to a
server system variable, use an option of the form
--
.
For example,
var_name
=value
--sort_buffer_size=384M
sets the
sort_buffer_size
variable to a
value of 384MB.
When you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.
To restrict the maximum value to which a system variable can be
set at runtime with the
SET
statement, specify this maximum by using an option of the form
--maximum-
at server startup.
var_name
=value
You can change the values of most system variables at runtime with
the SET
statement. See Section 13.7.4.1, “SET Syntax for Variable Assignment”.
Section 5.1.7, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. For information on changing system variables, see Section 5.1.1, “Configuring the Server”.
--help
, -?
Property | Value |
---|---|
Command-Line Format | --help |
Display a short help message and exit. Use both the
--verbose
and
--help
options to see the full
message.
Property | Value |
---|---|
Command-Line Format | --allow-suspicious-udfs[={OFF|ON}] |
Type | Boolean |
Default Value | OFF |
This option controls whether user-defined functions that have
only an xxx
symbol for the main function
can be loaded. By default, the option is off and only UDFs
that have at least one auxiliary symbol can be loaded; this
prevents attempts at loading functions from shared object
files other than those containing legitimate UDFs. See
UDF Security Precautions.
Property | Value |
---|---|
Command-Line Format | --ansi |
Use standard (ANSI) SQL syntax instead of MySQL syntax. For
more precise control over the server SQL mode, use the
--sql-mode
option instead. See
Section 1.8, “MySQL Standards Compliance”, and
Section 5.1.10, “Server SQL Modes”.
--basedir=
,
dir_name
-b
dir_name
Property | Value |
---|---|
Command-Line Format | --basedir=dir_name |
System Variable | basedir |
Scope | Global |
Dynamic | No |
Type | Directory name |
Default Value | configuration-dependent default |
The path to the MySQL installation directory. This option sets
the basedir
system variable.
Property | Value |
---|---|
Command-Line Format | --bootstrap |
Deprecated | 5.7.6 |
This option is used by the mysql_install_db program to create the MySQL privilege tables without having to start a full MySQL server.
mysql_install_db is deprecated because
its functionality has been integrated into
mysqld, the MySQL server. Consequently,
the --bootstrap
server option
that mysql_install_db passes to
mysqld is also deprecated. To initialize
a MySQL installation, invoke mysqld with
the --initialize
or
--initialize-insecure
option.
For more information, see
Section 2.10.1, “Initializing the Data Directory”.
mysql_install_db and the
--bootstrap
server option
will be removed in a future MySQL release.
--bootstrap
is mutually
exclusive with --daemonize
,
--initialize
, and
--initialize-insecure
.
Global transaction identifiers (GTIDs) are not disabled when
--bootstrap
is used.
--bootstrap
was used (Bug
#20980271). See Section 16.1.3, “Replication with Global Transaction Identifiers”.
When the server operates in bootstap mode, some functionality
is unavailable that limits the statements permitted in any
file named by the init_file
system variable. For more information, see the description of
that variable. In addition, the
disabled_storage_engines
system variable has no effect.
--character-set-client-handshake
Property | Value |
---|---|
Command-Line Format | --character-set-client-handshake[={OFF|ON}] |
Type | Boolean |
Default Value | ON |
Do not ignore character set information sent by the client. To
ignore client information and use the default server character
set, use
--skip-character-set-client-handshake
;
this makes MySQL behave like MySQL 4.0.
--chroot=
,
dir_name
-r
dir_name
Property | Value |
---|---|
Command-Line Format | --chroot=dir_name |
Type | Directory name |
Put the mysqld server in a closed
environment during startup by using the
chroot()
system call. This is a recommended
security measure. Use of this option somewhat limits
LOAD DATA
and
SELECT ... INTO
OUTFILE
.
Property | Value |
---|---|
Command-Line Format | --console |
Platform Specific | Windows |
(Windows only.) Write the error log to
stderr
and stdout
(the
console). mysqld does not close the console
window if this option is used.
--console
takes precedence over
--log-error
if both are given.
(In MySQL 5.5 and 5.6, this is reversed:
--log-error
takes precedence
over --console
if both are
given.)
Property | Value |
---|---|
Command-Line Format | --core-file[={OFF|ON}] |
Type | Boolean |
Default Value | OFF |
Write a core file if mysqld dies. The name
and location of the core file is system dependent. On Linux, a
core file named
core.
is
written to the current working directory of the process, which
for mysqld is the data directory.
pid
pid
represents the process ID of
the server process. On macOS, a core file 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.
Property | Value |
---|---|
Command-Line Format | --daemonize[={OFF|ON}] |
Introduced | 5.7.6 |
Type | Boolean |
Default Value | OFF |
This option causes the server to run as a traditional, forking daemon, permitting it to work with operating systems that use systemd for process control. For more information, see Section 2.5.10, “Managing MySQL Server with systemd”.
--daemonize
is mutually
exclusive with --bootstrap
,
--initialize
, and
--initialize-insecure
.
--datadir=
,
dir_name
-h
dir_name
Property | Value |
---|---|
Command-Line Format | --datadir=dir_name |
System Variable | datadir |
Scope | Global |
Dynamic | No |
Type | Directory name |
The path to the MySQL server data directory. This option sets
the datadir
system variable.
See the description of that variable.
--debug[=
,
debug_options
]-# [
debug_options
]
Property | Value |
---|---|
Command-Line Format | --debug[=debug_options] |
System Variable | debug |
Scope | Global, Session |
Dynamic | Yes |
Type | String |
Default Value (Windows) | d:t:i:O,\mysqld.trace |
Default Value (Unix) | d:t:i:o,/tmp/mysqld.trace |
If MySQL is configured with the
-DWITH_DEBUG=1
CMake option, you can use this option to
get a trace file of what mysqld is doing. A
typical debug_options
string is
d:t:o,
.
The default is file_name
d: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 28.5.3, “The DBUG Package”.
Property | Value |
---|---|
Command-Line Format | --debug-sync-timeout[=#] |
Type | Integer |
Controls whether the Debug Sync facility for testing and
debugging is enabled. Use of Debug Sync requires that MySQL be
configured with the
-DENABLE_DEBUG_SYNC=1
CMake option (see
Section 2.9.7, “MySQL Source-Configuration Options”). If Debug Sync
is not compiled in, this option is not available. The option
value is a timeout in seconds. The default value is 0, which
disables Debug Sync. To enable it, specify a value greater
than 0; this value also becomes the default timeout for
individual synchronization points. If the option is given
without a value, the timeout is set to 300 seconds.
For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.
--default-authentication-plugin=
plugin_name
Property | Value |
---|---|
Command-Line Format | --default-authentication-plugin=plugin_name |
Removed | 5.7.2 |
Type | Enumeration |
Default Value | mysql_native_password |
Valid Values |
|
This option sets the default authentication plugin. It was
removed in MySQL 5.7.2 and replaced by the
default_authentication_plugin
system variable. The variable is used the same way as the
option at server startup, but also enables the default plugin
value to be inspected as runtime. For usage details, see the
description of
default_authentication_plugin
.
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 |
Deprecated | 5.7.6 |
Read the default DES keys from this file. These keys are used
by the DES_ENCRYPT()
and
DES_DECRYPT()
functions.
The DES_ENCRYPT()
and
DES_DECRYPT()
functions are
deprecated in MySQL 5.7, will be removed in a
future MySQL release, and should no longer be used.
Consequently, --des-key-file
also is deprecated and will be removed.
--disable-partition-engine-check
Property | Value |
---|---|
Command-Line Format | --disable-partition-engine-check[={OFF|ON}] |
Introduced | 5.7.17 |
Deprecated | 5.7.17 |
Type | Boolean |
Default Value (>= 5.7.21) | ON |
Default Value (>= 5.7.17, <= 5.7.20) | OFF |
Whether to disable the startup check for tables with nonnative partitioning.
As of MySQL 5.7.17, the generic partitioning handler in the
MySQL server is deprecated, and is removed in MySQL
8.0, when the storage engine used for a given table
is expected to provide its own (“native”)
partitioning handler. Currently, only the
InnoDB
and
NDB
storage engines do this.
Use of tables with nonnative partitioning results in an
ER_WARN_DEPRECATED_SYNTAX
warning. In MySQL 5.7.17 through 5.7.20, the server
automatically performs a check at startup to identify tables
that use nonnative partitioning; for any that are found, the
server writes a message to its error log. To disable this
check, use the
--disable-partition-engine-check
option. In MySQL 5.7.21 and later, this check is
not performed; in these versions, you
must start the server with
--disable-partition-engine-check=false
,
if you wish for the server to check for tables using the
generic partitioning handler (Bug #85830, Bug #25846957).
Use of tables with nonnative partitioning results in an
ER_WARN_DEPRECATED_SYNTAX
warning. Also, the server performs a check at startup to
identify tables that use nonnative partitioning; for any
found, the server writes a message to its error log. To
disable this check, use the
--disable-partition-engine-check
option.
To prepare for migration to MySQL 8.0, any table
with nonnative partitioning should be changed to use an engine
that provides native partitioning, or be made nonpartitioned.
For example, to change a table to InnoDB
,
execute this statement:
ALTER TABLE table_name
ENGINE = INNODB;
--early-plugin-load=
plugin_list
Property | Value |
---|---|
Command-Line Format | --early-plugin-load=plugin_list |
Introduced | 5.7.11 |
Type | String |
Default Value (>= 5.7.12) | empty string |
Default Value (5.7.11) | keyring_file plugin library file name |
This option tells the server which plugins to load before
loading mandatory built-in plugins and before storage engine
initialization. If multiple
--early-plugin-load
options are
given, only the last one is used.
The option value is a semicolon-separated list of
name
=
plugin_library
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 --early-plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
Quotes are used around the argument value because otherwise a
semicolon (;
) is interpreted as a special
character by some command interpreters. (Unix shells treat it
as a command terminator, for example.)
Each named plugin is loaded early for a single invocation of
mysqld only. After a restart, the plugin is
not loaded early unless
--early-plugin-load
is used
again.
If the server is started using
--initialize
or
--initialize-insecure
, plugins
specified by
--early-plugin-load
are not
loaded.
If the server is run with
--help
, plugins specified by
--early-plugin-load
are loaded
but not initialized. This behavior ensures that plugin options
are displayed in the help message.
As of MySQL 5.7.12, the default
--early-plugin-load
value is
empty. To load your chosen keyring plugin, you must use an
explicit --early-plugin-load
option with a nonempty value.
In MySQL 5.7.11, the default
--early-plugin-load
value was
the name of the keyring_file
plugin
library file, so that plugin was loaded by default.
InnoDB
tablespace encryption requires the
keyring_file
plugin to be loaded prior to
InnoDB
initialization, so this change of
default --early-plugin-load
value introduces an incompatibility for upgrades from 5.7.11
to 5.7.12 or higher. Administrators who have encrypted
InnoDB
tablespaces must take explicit
action to ensure continued loading of the
keyring_file
plugin: Start the server
with an --early-plugin-load
option that names the plugin library file. For additional
information, see Section 6.4.4.1, “Keyring Plugin Installation”.
The InnoDB
tablespace encryption feature
relies on the keyring_file
plugin for
encryption key management, and the
keyring_file
plugin must be loaded prior to
storage engine initialization to facilitate
InnoDB
recovery for encrypted tables. In
MySQL 5.7.11, if you do not want to load the
keyring_file
plugin at server startup,
specify an empty string
(--early-plugin-load=""
).
For information about InnoDB
tablespace
encryption, see Section 14.14, “InnoDB Data-at-Rest Encryption”. For
general information about plugin loading, see
Section 5.5.1, “Installing and Uninstalling Plugins”.
--exit-info[=
,
flags
]-T [
flags
]
Property | Value |
---|---|
Command-Line Format | --exit-info[=flags] |
Type | Integer |
This is a bitmask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!
Property | Value |
---|---|
Command-Line Format | --external-locking[={OFF|ON}] |
Type | Boolean |
Default Value | OFF |
Enable external locking (system locking), which is disabled by
default. If you use this option on a system on which
lockd
does not fully work (such as Linux),
it is easy for mysqld to deadlock.
To disable external locking explicitly, use
--skip-external-locking
.
External locking affects only
MyISAM
table access. For more
information, including conditions under which it can and
cannot be used, see Section 8.11.5, “External Locking”.
Property | Value |
---|---|
Command-Line Format | --flush[={OFF|ON}] |
System Variable | flush |
Scope | Global |
Dynamic | Yes |
Type | Boolean |
Default Value | OFF |
Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.4.3.3, “What to Do If MySQL Keeps Crashing”.
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 28.5.1.4, “Debugging mysqld under gdb”.
Property | Value |
---|---|
Command-Line Format | --ignore-db-dir=dir_name |
Deprecated | 5.7.16 |
Type | Directory name |
This option tells the server to ignore the given directory
name for purposes of the SHOW
DATABASES
statement 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.
This option is deprecated in MySQL 5.7. With the introduction of the data dictionary in MySQL 8.0, it became superfluous and was removed in that version.
Property | Value |
---|---|
Command-Line Format | --initialize[={OFF|ON}] |
Introduced | 5.7.6 |
Type | Boolean |
Default Value | OFF |
This option is used to initialize a MySQL installation by
creating the data directory and populating the tables in the
mysql
system database. For more
information, see
Section 2.10.1, “Initializing the Data Directory”.
When the server is started with
--initialize
, some
functionality is unavailable that limits the statements
permitted in any file named by 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.
In MySQL NDB Cluster 7.5.4 and later, the
--ndbcluster
option is ignored
when used together with --initialize
. (Bug
#81689, Bug #23518923)
In MySQL 5.7.7 and earlier, global transaction identifiers
(GTIDs) were automatically disabled whenever
--initialize
was enabled. In
MySQL 5.7.8 and later GTIDs are not disabled when
--initialize
is enabled.
--initialize
is mutually
exclusive with --bootstrap
and
--daemonize
.
Property | Value |
---|---|
Command-Line Format | --initialize-insecure[={OFF|ON}] |
Introduced | 5.7.6 |
Type | Boolean |
Default Value | OFF |
This option is used to initialize a MySQL installation by
creating the data directory and populating the tables in the
mysql
system database. This option implies
--initialize
. For more
information, see the description of that option, and
Section 2.10.1, “Initializing the Data Directory”.
--initialize-insecure
is
mutually exclusive with
--bootstrap
and
--daemonize
.
--innodb-
xxx
Set an option for the InnoDB
storage
engine. The InnoDB
options are listed in
Section 14.15, “InnoDB Startup Options and System Variables”.
Property | Value |
---|---|
Command-Line Format | --install [service_name] |
Platform Specific | Windows |
(Windows only) Install the server as a Windows service that
starts automatically during Windows startup. The default
service name is MySQL
if no
service_name
value is given. For
more information, see Section 2.3.4.8, “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
]
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 2.3.4.8, “Starting MySQL as a Windows Service”.
If the server is started with the
--defaults-file
and
--install-manual
options,
--install-manual
must be
first.
--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 2.3.4.8, “Starting MySQL as a Windows Service”.
Property | Value |
---|---|
Command-Line Format | --log-error[=file_name] |
System Variable | log_error |
Scope | Global |
Dynamic | No |
Type | File name |
Write the error log and startup messages to this file. See Section 5.4.2, “The Error Log”.
If the option names no file, the error log file name on Unix
and Unix-like systems is
in the data directory. The file name on Windows is the same,
unless the 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, --console
takes
precedence over --log-error
if
both are given. In this case, the server writes the error log
to the console rather than to a file. (In MySQL 5.5 and 5.6,
this is reversed: --log-error
takes precedence over --console
if both are given.)
Property | Value |
---|---|
Command-Line Format | --log-isam[=file_name] |
Type | File name |
Log all MyISAM
changes to this file (used
only when 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.
If a query rewrite plugin is installed, the
--log-raw
option affects
statement logging as follows:
For more information, see Section 6.1.2.3, “Passwords and Logging”.
Property | Value |
---|---|
Command-Line Format | --log-short-format[={OFF|ON}] |
Type | Boolean |
Default Value | OFF |
Log less information to the slow query log, if it has been activated.
Property | Value |
---|---|
Command-Line Format | --log-slow-admin-statements[={OFF|ON}] (5.7.0) |
Removed | 5.7.1 |
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 5.7.1 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 (64-bit platforms, >= 5.7.21) | 6 * page size |
Default Value (64-bit platforms, <= 5.7.20) | 24576 |
Default Value (32-bit platforms, >= 5.7.21) | 6 * page size |
Default Value (32-bit platforms, <= 5.7.20) | 24576 |
Minimum Value | 6 * page size |
Maximum Value (64-bit platforms) | 18446744073709551615 |
Maximum Value (32-bit platforms) | 4294967295 |
The size in bytes of the memory-mapped transaction coordinator log. The default and minimum values are 6 times the page size, and the value must be a multiple of the page size. (Before MySQL 5.7.21, the default size is 24KB.)
--log-warnings[=
,
level
]-W [
level
]
Property | Value |
---|---|
Command-Line Format | --log-warnings[=#] |
Deprecated | 5.7.2 |
System Variable | log_warnings |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value (64-bit platforms, >= 5.7.2) | 2 |
Default Value (64-bit platforms, <= 5.7.1) | 1 |
Default Value (32-bit platforms, >= 5.7.2) | 2 |
Default Value (32-bit platforms, <= 5.7.1) | 1 |
Minimum Value | 0 |
Maximum Value (64-bit platforms) | 18446744073709551615 |
Maximum Value (32-bit platforms) | 4294967295 |
As of MySQL 5.7.2, the
log_error_verbosity
system
variable is preferred over, and should be used instead of,
the --log-warnings
option or
log_warnings
system
variable. For more information, see the descriptions of
log_error_verbosity
and
log_warnings
. The
--log-warnings
command-line
option and log_warnings
system variable are deprecated and will be removed in a
future MySQL release.
Whether to produce additional warning messages to the error
log. This option is enabled by default (the default is 1
before MySQL 5.7.2, 2 as of 5.7.2). To disable it, use
--log-warnings=0
. Specifying
the option without a level
value
increments the current value by 1. The server logs messages
about statements that are unsafe for statement-based logging
if the value is greater than 0. Aborted connections and
access-denied errors for new connection attempts are logged if
the value is greater than 1. See
Section B.4.2.10, “Communication Errors and Aborted Connections”.
Property | Value |
---|---|
Command-Line Format | --memlock[={OFF|ON}] |
Type | Boolean |
Default Value | OFF |
Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.
--memlock
works on systems that
support 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 6.2.16, “Setting Account Resource Limits”.
Property | Value |
---|---|
Command-Line Format | --partition[={OFF|ON}] |
Deprecated | 5.7.16 |
Disabled by | skip-partition |
Type | Boolean |
Default Value | ON |
Enables or disables user-defined partitioning support in the MySQL Server.
This option is deprecated in MySQL 5.7.16, and is removed from MySQL 8.0 because in MySQL 8.0, the partitioning engine is replaced by native partitioning, which cannot be disabled.
--performance-schema-xxx
Configure a Performance Schema option. For details, see Section 25.14, “Performance Schema Command Options”.
Property | Value |
---|---|
Command-Line Format | --plugin-load=plugin_list |
System Variable | plugin_load |
Scope | Global |
Dynamic | No |
Type | String |
This option tells the server to load the named plugins at
startup. If multiple
--plugin-load
options are
given, only the last one is used. Additional plugins to load
may be specified using
--plugin-load-add
options.
The option value is a semicolon-separated list of
name
=
plugin_library
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. 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 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 2.3.4.8, “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.
--skip-grant-tables
causes
the
disabled_storage_engines
system variable to have no effect.
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 8.12.5.2, “DNS Lookup Optimization 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 5.7.5, the InnoDB
storage
engine can no longer be disabled, and the
--skip-innodb
option is deprecated and has no effect. 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 |
|
Deprecated | 5.7.16 |
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
partition definitions associated with partitioned tables in
such cases. For this reason, you should avoid dropping
partitioned tables with partitioning disabled, or take action
to remove orphaned .par
files manually
(if present).
As of MySQL 5.7.6, partition definition
(.par
) files are no longer created for
partitioned InnoDB
tables. Instead,
partition definitions are stored in the
InnoDB
internal data dictionary.
Partition definition (.par
) files
continue to be used for partitioned
MyISAM
tables.
This option is deprecated in MySQL 5.7.16, and is removed from MySQL 8.0 because in MySQL 8.0, the partitioning engine is replaced by native partitioning, which cannot be disabled.
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 28.5, “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 (>= 5.7.8) | ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_ZERO_IN_DATE NO_ZERO_DATE ERROR_FOR_DIVISION_BY_ZERO NO_AUTO_CREATE_USER NO_ENGINE_SUBSTITUTION |
Default Value (5.7.7) | ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_AUTO_CREATE_USER NO_ENGINE_SUBSTITUTION |
Default Value (>= 5.7.5, <= 5.7.6) | ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_ENGINE_SUBSTITUTION |
Default Value (<= 5.7.4) | NO_ENGINE_SUBSTITUTION |
Valid Values |
|
Set the SQL mode. See Section 5.1.10, “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.
Options that begin with --ssl
specify whether to permit clients to connect using SSL and
indicate where to find SSL keys and certificates. See
Command Options for Encrypted Connections.
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. 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”.
This option has no meaning on Windows.
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 12.7, “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 | COMMIT |
Valid Values |
|
The type of decision to use in the heuristic recovery process. To use this option, two or more storage engines that support XA transactions must be installed.
Property | Value |
---|---|
Command-Line Format | --temp-pool[={OFF|ON}] |
Deprecated | 5.7.18 |
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.
As of MySQL 5.7.18, this option is deprecated and is removed in MySQL 8.0.
Property | Value |
---|---|
Command-Line Format | --transaction-isolation=name |
System Variable (>= 5.7.20) | transaction_isolation |
Scope (>= 5.7.20) | Global, Session |
Dynamic (>= 5.7.20) | Yes |
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
(or, as of MySQL
5.7.20,
transaction_isolation
) system
variable.
Property | Value |
---|---|
Command-Line Format | --transaction-read-only[={OFF|ON}] |
System Variable (>= 5.7.20) | transaction_read_only |
Scope (>= 5.7.20) | Global, Session |
Dynamic (>= 5.7.20) | Yes |
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
(or, as
of MySQL 5.7.20,
transaction_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.