When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.3, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 4.2.3.3, “Using Option Files”.
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 mysqld --help. To see the full list, use mysqld --verbose --help.
The following list shows some of the most common server options. Additional options are described in other sections:
Options that affect security: See Section 6.1.4, “Security-Related mysqld Options and Variables”.
SSL-related options: See Section 6.3.6.4, “SSL Command Options”.
Binary log control options: See Section 16.1.2.4, “Binary Log Options and Variables”.
Replication-related options: See Section 16.1.2, “Replication and Binary Logging Options and Variables”.
Options specific to particular storage engines: See
Section 14.1.1, “MyISAM Startup Options”, Section 14.5.3, “BDB Startup Options”,
Section 14.2.2, “InnoDB Startup Options and System Variables”, and
Section 17.3.4.2, “mysqld Command Options for MySQL Cluster”.
You can also set the values of server system variables by using variable names as options, as described at the end of this section.
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.
--help, -?
| Command-Line Format | -? | ||
--help | |||
| Option-File Format | help | ||
Display a short help message and exit. Use both the
--verbose and
--help options to see the full
message.
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --allow-suspicious-udfs | ||
| Option-File Format | allow-suspicious-udfs | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
This option controls whether user-defined functions that have
only an xxx symbol for the main function
can be loaded. By default, the option is off and only UDFs
that have at least one auxiliary symbol can be loaded; this
prevents attempts at loading functions from shared object
files other than those containing legitimate UDFs. This option
was added in version 5.0.3. See
Section 21.2.2.6, “User-Defined Function Security Precautions”.
| Command-Line Format | --ansi | ||
-a | |||
| Option-File 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 1.8.3, “Running MySQL in ANSI Mode”, and
Section 5.1.7, “Server SQL Modes”.
| Command-Line Format | --basedir=path | ||
-b | |||
| Option-File Format | basedir | ||
| Option Sets Variable | Yes, basedir | ||
| Variable Name | basedir | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
The path to the MySQL installation directory. All paths are usually resolved relative to this directory.
| Command-Line Format | --big-tables | ||
| Option-File Format | big-tables | ||
| Option Sets Variable | Yes, big_tables | ||
| Variable Name | big-tables | ||
| Variable Scope | Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
Enable large result sets by saving all temporary sets in files. This option prevents most “table full” errors, but also slows down queries for which in-memory tables would suffice. Since MySQL 3.23.2, the server is able to handle large result sets automatically by using memory for small temporary tables and switching to disk tables where necessary.
| Command-Line Format | --bind-address=addr | ||
| Option-File Format | bind-address=addr | ||
| Variable Name | bind-address | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
The MySQL server listens on a single network socket for TCP/IP
connections. This socket is bound to a single address, but it
is possible for an address to map onto multiple network
interfaces. The default address is 0.0.0.0.
To specify an address explicitly, use the
--bind-address=
option at server startup, where
addraddr is an IPv4 address or a host
name. If addr is a host name, the
server resolves the name to an IPv4 address and binds to that
address.
The server treats different types of addresses as follows:
If the address is 0.0.0.0, the server
accepts TCP/IP connections on all server host IPv4
interfaces.
If the address is a “regular” IPv4 address
(such as 127.0.0.1), the server accepts
TCP/IP connections only for that particular IPv4 address.
If you intend to bind the server to a specific address, be
sure that the mysql.user grant table
contains an account with administrative privileges that you
can use connect to that address. Otherwise, you will not be
able to shut down the server. For example, if you bind to
0.0.0.0, you can connect to the server
using all existing accounts. But if you bind to
127.0.0.1, the server accepts connections
only on that address. In this case, first make sure that the
'root'@'127.0.0.1' account is present in
the mysql.user table so that you can still
connect to the server to shut it down.
| Command-Line Format | --bootstrap | ||
| Option-File Format | bootstrap | ||
This option is used by the mysql_install_db script to create the MySQL privilege tables without having to start a full MySQL server.
This option is unavailable if MySQL was configured with the
--disable-grant-options
option. See Section 2.17.3, “MySQL Source-Configuration Options”.
| Command-Line Format | --character-sets-dir=path | ||
| Option-File Format | character-sets-dir=path | ||
| Option Sets Variable | Yes, character_sets_dir | ||
| Variable Name | character-sets-dir | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | directory name | ||
The directory where character sets are installed. See Section 10.5, “Character Set Configuration”.
--character-set-client-handshake
| Command-Line Format | --character-set-client-handshake | ||
| Option-File Format | character-set-client-handshake | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | TRUE | ||
Do not ignore character set information sent by the client. To
ignore client information and use the default server character
set, use
--skip-character-set-client-handshake;
this makes MySQL behave like MySQL 4.0.
--character-set-filesystem=
charset_name
| Version Introduced | 5.0.19 | ||
| Command-Line Format | --character-set-filesystem=name | ||
| Option-File Format | character-set-filesystem | ||
| Option Sets Variable | Yes, character_set_filesystem | ||
| Variable Name | character_set_filesystem | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | string | ||
The file system character set. This option sets the
character_set_filesystem
system variable. It was added in MySQL 5.0.19.
--character-set-server=,
charset_name-C
charset_name
| Command-Line Format | --character-set-server | ||
| Option-File Format | character-set-server | ||
| Option Sets Variable | Yes, character_set_server | ||
| Variable Name | character_set_server | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | string | ||
Use charset_name as the default
server character set. See
Section 10.5, “Character Set Configuration”. If you use this
option to specify a nondefault character set, you should also
use --collation-server to
specify the collation.
--chroot=,
path-r
path
| Command-Line Format | --chroot=name | ||
-r name | |||
| Option-File Format | chroot | ||
| Permitted Values | |||
| Type | file name | ||
Put the mysqld server in a closed
environment during startup by using the
chroot() system call. This is a recommended
security measure. Note that use of this option somewhat limits
LOAD DATA
INFILE and
SELECT ... INTO
OUTFILE.
--collation-server=
collation_name
| Command-Line Format | --collation-server | ||
| Option-File Format | collation-server | ||
| Option Sets Variable | Yes, collation_server | ||
| Variable Name | collation_server | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | string | ||
Use collation_name as the default
server collation. See Section 10.5, “Character Set Configuration”.
| Command-Line Format | --console | ||
| Option-File Format | console | ||
| Platform Specific | windows | ||
(Windows only.) Write error log messages to
stderr and stdout.
mysqld does not close the console window if
this option is used.
If both --log-error and
--console are specified,
whichever option is given last takes precedence.
| Command-Line Format | --core-file | ||
| Option-File Format | core-file | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | OFF | ||
Write a core file if mysqld dies. The name
and location of the core file is system dependent. On Linux, a
core file named
core. 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 Mac OS X, 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=,
path-h
path
| Command-Line Format | --datadir=path | ||
-h | |||
| Option-File Format | datadir | ||
| Option Sets Variable | Yes, datadir | ||
| Variable Name | datadir | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
The path to the data directory.
--debug[=,
debug_options]-# [
debug_options]
| Command-Line Format | --debug[=debug_options] | ||
| Option-File Format | debug | ||
| Variable Name | debug | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | string | ||
| Default | 'd:t:o,/tmp/mysqld.trace' | ||
If MySQL is configured with
--with-debug, you can use
this option to get a trace file of what
mysqld is doing. A typical
debug_options string is
'd:t:o,.
The default is file_name''d:t:i:o,mysqld.trace'. See
MySQL
Internals: Porting to Other Systems.
As of MySQL 5.0.25, using
--with-debug to configure
MySQL with debugging support enables you to use the
--debug="d,parser_debug" option
when you start the server. This causes the Bison parser that
is used to process SQL statements to dump a parser trace to
the server's standard error output. Typically, this output is
written to the error log.
--default-character-set=
charset_name
| Version Deprecated | 5.0 | ||
| Command-Line Format | --default-character-set=name | ||
-C name | |||
| Option-File Format | default-character-set=name | ||
| Deprecated | 5.0 | ||
| Permitted Values | |||
| Type | string | ||
Use charset_name as the default
character set. This option is deprecated in favor of
--character-set-server. See
Section 10.5, “Character Set Configuration”.
--default-character-set is
removed in MySQL 5.5.
--default-collation=
collation_name
| Command-Line Format | --default-collation=name | ||
| Option-File Format | default-collation=name | ||
| Deprecated | 4.1.3 | ||
| Permitted Values | |||
| Type | string | ||
Use collation_name as the default
collation. This option is deprecated in favor of
--collation-server. See
Section 10.5, “Character Set Configuration”.
--default-collation is removed
in MySQL 5.5.
| Command-Line Format | --default-storage-engine=name | ||
| Option-File Format | default-storage-engine | ||
| Variable Name | storage_engine | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
Set the default storage engine (table type) for tables. See Chapter 14, Storage Engines.
| Version Deprecated | 5.0, by default-storage-engine | ||
| Command-Line Format | --default-table-type=name | ||
| Option-File Format | default-table-type | ||
| Deprecated | 5.0, by default-storage-engine | ||
| Permitted Values | |||
| Type | string | ||
This option is a deprecated synonym for
--default-storage-engine.
| Command-Line Format | --default-time-zone=name | ||
| Option-File Format | default-time-zone | ||
| Permitted Values | |||
| Type | string | ||
Set the default server time zone. This option sets the global
time_zone system variable. If
this option is not given, the default time zone is the same as
the system time zone (given by the value of the
system_time_zone system
variable.
--delay-key-write[={OFF|ON|ALL}]
| Command-Line Format | --delay-key-write[=name] | ||
| Option-File Format | delay-key-write | ||
| Option Sets Variable | Yes, delay_key_write | ||
| Variable Name | delay-key-write | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | enumeration | ||
| Default | ON | ||
| Valid Values | ON | ||
OFF | |||
ALL | |||
Specify how to use delayed key writes. Delayed key writing
causes key buffers not to be flushed between writes for
MyISAM tables. OFF
disables delayed key writes. ON enables
delayed key writes for those tables that were created with the
DELAY_KEY_WRITE option.
ALL delays key writes for all
MyISAM tables. See
Section 8.9.2, “Tuning Server Parameters”, and
Section 14.1.1, “MyISAM Startup Options”.
If you set this variable to ALL, you
should not use MyISAM tables from within
another program (such as another MySQL server or
myisamchk) when the tables are in use.
Doing so leads to index corruption.
| Command-Line Format | --des-key-file=file_name | ||
| Option-File 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.
This option is deprecated. Use
--external-locking instead.
| Command-Line Format | --enable-named-pipe | ||
| Option-File Format | enable-named-pipe | ||
| Option Sets Variable | Yes, named_pipe | ||
| Platform Specific | windows | ||
Enable support for named pipes. This option can be used only with the mysqld-nt and mysqld-debug servers that support named-pipe connections.
| Command-Line Format | --enable-pstack | ||
| Option-File Format | enable-pstack | ||
| Deprecated | 5.1.54 | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Print a symbolic stack trace on failure. This capability is
available only on Intel Linux systems, and only if MySQL was
configured with the --with-pstack option.
--engine-condition-pushdown={ON|OFF}
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --engine-condition-pushdown | ||
| Option-File Format | engine-condition-pushdown | ||
| Option Sets Variable | Yes, engine_condition_pushdown | ||
| Variable Name | engine_condition_pushdown | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Deprecated | 5.5.3, by optimizer_switch | ||
| Permitted Values (>= 5.0.3) | |||
| Type | boolean | ||
| Default | OFF | ||
Sets the
engine_condition_pushdown
system variable. For more information, see
Section 8.3.1.5, “Engine Condition Pushdown Optimization”.
This variable was added in MySQL 5.0.3.
--exit-info[=,
flags]-T [
flags]
| Command-Line Format | --exit-info[=flags] | ||
-T [flags] | |||
| Option-File Format | exit-info | ||
| Permitted Values | |||
| Type | numeric | ||
This is a bit mask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!
| Command-Line Format | --external-locking | ||
| Option-File Format | external-locking | ||
| Option Sets Variable | Yes, skip_external_locking | ||
| Disabled by | skip-external-locking | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Enable external locking (system locking), which is disabled by
default as of MySQL 4.0. Note that if you use this option on a
system on which lockd does not fully work
(such as Linux), it is easy for mysqld to
deadlock. This option previously was named
--enable-locking.
External locking affects only
MyISAM table access. For more
information, including conditions under which it can and
cannot be used, see Section 8.7.4, “External Locking”.
| Command-Line Format | --flush | ||
| Option-File Format | flush | ||
| Variable Name | flush | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | OFF | ||
Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section C.5.4.2, “What to Do If MySQL Keeps Crashing”.
| Command-Line Format | --gdb | ||
| Option-File Format | gdb | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Install an interrupt handler for SIGINT
(needed to stop mysqld with
^C to set breakpoints) and disable stack
tracing and core file handling. See
MySQL
Internals: Porting to Other Systems.
| Command-Line Format | --init-file=file_name | ||
| Option-File Format | init-file=file_name | ||
| Option Sets Variable | Yes, init_file | ||
| Variable Name | init_file | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
Read SQL statements from this file at startup. Each statement must be on a single line and should not include comments.
This option is unavailable if MySQL was configured with the
--disable-grant-options
option. See Section 2.17.3, “MySQL Source-Configuration Options”.
| Version Removed | 5.0.3 | ||
| Version Deprecated | 5.0.3 | ||
| Command-Line Format | --innodb-safe-binlog | ||
| Option-File Format | innodb-safe-binlog | ||
| Deprecated | 5.0.3 | ||
| Permitted Values | |||
| Type | boolean | ||
If this option is given, then after a crash recovery by
InnoDB, mysqld truncates
the binary log after the last not-rolled-back transaction in
the log. The option also causes InnoDB to
print an error if the binary log is smaller or shorter than it
should be. See Section 5.2.3, “The Binary Log”. This option was
removed in MySQL 5.0.3, having been made obsolete by the
introduction of XA transaction support.
--innodb-
xxx
Set an option for the InnoDB storage
engine. The InnoDB options are listed in
Section 14.2.2, “InnoDB Startup Options and System Variables”.
| Command-Line Format | --install [service_name] | ||
(Windows only) Install the server as a Windows service that
starts automatically during Windows startup. The default
service name is MySQL if no
service_name value is given. For
more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.
--install-manual
[
service_name]
| Command-Line Format | --install-manual [service_name] | ||
(Windows only) Install the server as a Windows service that
must be started manually. It does not start automatically
during Windows startup. The default service name is
MySQL if no
service_name value is given. For
more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.
--language=
lang_name,
-L lang_name
| Command-Line Format | --language=name | ||
-L | |||
| Option-File Format | language | ||
| Option Sets Variable | Yes, language | ||
| Variable Name | language | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Deprecated | 5.6.1 | ||
| Permitted Values | |||
| Type | directory name | ||
| Default | /usr/local/mysql/share/mysql/english/ | ||
The language to use for error messages.
lang_name can be given as the
language name or as the full path name to the directory where
the language files are installed. See
Section 10.2, “Setting the Error Message Language”.
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --large-pages | ||
| Option-File Format | large-pages | ||
| Option Sets Variable | Yes, large_pages | ||
| Variable Name | large_pages | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Platform Specific | linux | ||
| Permitted Values | |||
| Type (linux) | boolean | ||
| Default | FALSE | ||
Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.
Currently, MySQL supports only the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.9.7, “Enabling Large Page Support”.
--large-pages is disabled by
default. It was added in MySQL 5.0.3.
--log[=,
file_name]-l [
file_name]
| Command-Line Format | --log[=name] | ||
-l | |||
| Option-File Format | log | ||
| Option Sets Variable | Yes, log | ||
| Variable Name | log | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Deprecated | 5.1.29, by general-log | ||
| Permitted Values | |||
| Type | string | ||
| Default | OFF | ||
Log connections and SQL statements received from clients to
this file. See Section 5.2.2, “The General Query Log”. If you omit the
file name, MySQL uses
as the file name.
host_name.log
| Command-Line Format | --log-error[=name] | ||
| Option-File Format | log-error | ||
| Option Sets Variable | Yes, log_error | ||
| Variable Name | log_error | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
Log errors and startup messages to this file. See
Section 5.2.1, “The Error Log”. If you omit the file name, MySQL
uses
.
If the file name has no extension, the server adds an
extension of host_name.err.err.
| Command-Line Format | --log-isam[=name] | ||
| Option-File Format | log-isam | ||
| Permitted Values | |||
| Type | file name | ||
Log all MyISAM changes to this file (used
only when debugging MyISAM).
| Command-Line Format | --log-long-format | ||
-0 | |||
| Option-File Format | log-long-format | ||
| Deprecated | 4.1 | ||
Log extra information to the update log, binary update log,
and slow query log, if they have been activated. For example,
the user name and timestamp are logged for all queries. This
option is deprecated, as it now represents the default logging
behavior. (See the description for
--log-short-format.) The
--log-queries-not-using-indexes
option is available for the purpose of logging queries that do
not use indexes to the slow query log.
--log-long-format is removed in
MySQL 5.5.
--log-queries-not-using-indexes
| Command-Line Format | --log-queries-not-using-indexes | ||
| Option-File Format | log-queries-not-using-indexes | ||
| Option Sets Variable | Yes, log_queries_not_using_indexes | ||
| Variable Name | log_queries_not_using_indexes | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | OFF | ||
If you are using this option with the slow query log enabled, queries that are expected to retrieve all rows are logged. See Section 5.2.4, “The Slow Query Log”. This option does not necessarily mean that no index is used. For example, a query that uses a full index scan uses an index but would be logged because the index would not limit the number of rows.
| Command-Line Format | --log-short-format | ||
| Option-File Format | log-short-format | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Originally intended to log less information to the update log, binary log and slow query log, if they have been activated. However, this option is not operational.
| Command-Line Format | --log-slow-admin-statements | ||
| Option-File Format | log-slow-admin-statements | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | OFF | ||
Include slow administrative statements in the statements
written to the slow query log. Administrative statements
include ALTER TABLE,
ANALYZE TABLE,
CHECK TABLE,
CREATE INDEX,
DROP INDEX,
OPTIMIZE TABLE, and
REPAIR TABLE.
--log-slow-queries[=
file_name]
| Command-Line Format | --log-slow-queries[=name] | ||
| Option-File Format | log-slow-queries | ||
| Option Sets Variable | Yes, log_slow_queries | ||
| Variable Name | log_slow_queries | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Deprecated | 5.1.29, by slow-query-log | ||
| Permitted Values | |||
| Type | boolean | ||
Log all queries that have taken more than
long_query_time seconds to
execute to this file. See Section 5.2.4, “The Slow Query Log”.
See the descriptions of the
--log-long-format and
--log-short-format options for
details.
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --log-tc=name | ||
| Option-File Format | log-tc | ||
| Permitted Values | |||
| Type | file name | ||
| Default | tc.log | ||
The name of the memory-mapped transaction coordinator log file
(for XA transactions that affect multiple storage engines when
the binary log is disabled). The default name is
tc.log. The file is created under the
data directory if not given as a full path name. Currently,
this option is unused. Added in MySQL 5.0.3.
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --log-tc-size=# | ||
| Option-File Format | log-tc-size | ||
| Permitted Values | |||
| Platform Bit Size | 32 | ||
| Type | numeric | ||
| Default | 24576 | ||
| Max Value | 4294967295 | ||
| Permitted Values | |||
| Platform Bit Size | 64 | ||
| Type | numeric | ||
| Default | 24576 | ||
| Max Value | 18446744073709547520 | ||
The size in bytes of the memory-mapped transaction coordinator log. The default size is 24KB. Added in MySQL 5.0.3.
--log-warnings[=,
level]-W [
level]
| Command-Line Format | --log-warnings[=#] | ||
-W [#] | |||
| Option-File Format | log-warnings | ||
| Option Sets Variable | Yes, log_warnings | ||
| Variable Name | log_warnings | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Disabled by | skip-log-warnings | ||
| Permitted Values | |||
| Platform Bit Size | 64 | ||
| Type | numeric | ||
| Default | 1 | ||
| Range | 0 .. 18446744073709547520 | ||
Print out warnings such as Aborted
connection... to the error log. Enabling this option
is recommended, for example, if you use replication (you get
more information about what is happening, such as messages
about network failures and reconnections). This option is
enabled (1) by default, and the default
level value if omitted is 1. To
disable this option, use
--log-warnings=0. If the value
is greater than 1, aborted connections are written to the
error log. See Section C.5.2.11, “Communication Errors and Aborted Connections”.
If a slave server was started with
--log-warnings enabled, the
slave prints messages to the error log to provide information
about its status, such as the binary log and relay log
coordinates where it starts its job, when it is switching to
another relay log, when it reconnects after a disconnect, and
so forth.
| Command-Line Format | --low-priority-updates | ||
| Option-File Format | low-priority-updates | ||
| Option Sets Variable | Yes, low_priority_updates | ||
| Variable Name | low_priority_updates | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Give table-modifying operations
(INSERT,
REPLACE,
DELETE,
UPDATE) lower priority than
selects. This can also be done using {INSERT |
REPLACE | DELETE | UPDATE} LOW_PRIORITY ... to lower
the priority of only one query, or by SET
LOW_PRIORITY_UPDATES=1 to change the priority in one
thread. This affects only storage engines that use only
table-level locking (MyISAM,
MEMORY, MERGE). See
Section 8.7.2, “Table Locking Issues”.
| Command-Line Format | --memlock | ||
| Option-File Format | memlock | ||
| Variable Name | locked_in_memory | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.
--memlock works on systems that
support the mlockall() system call; this
includes Solaris, most Linux distributions that use a 2.4 or
newer kernel, and perhaps other Unix systems. On Linux
systems, you can tell whether or not
mlockall() (and thus this option) is
supported by checking to see whether or not it is defined in
the system mman.h file, like this:
shell> grep mlockall /usr/include/sys/mman.h
If mlockall() is supported, you should see
in the output of the previous command something like the
following:
extern int mlockall (int __flags) __THROW;
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 8.9.7, “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.
| Command-Line Format | --myisam-block-size=# | ||
| Option-File Format | myisam-block-size | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 1024 | ||
| Range | 1024 .. 16384 | ||
The block size to be used for MyISAM index
pages.
--myisam-recover[=
option[,option]...]]
| Command-Line Format | --myisam-recover[=name] | ||
| Option-File Format | myisam-recover | ||
| Option Sets Variable | Yes, myisam_recover_options | ||
| Permitted Values | |||
| Type | enumeration | ||
| Default | OFF | ||
| Valid Values | DEFAULT | ||
BACKUP | |||
FORCE | |||
QUICK | |||
Set the MyISAM storage engine recovery
mode. The option value is any combination of the values of
DEFAULT, BACKUP,
FORCE, or QUICK. If you
specify multiple values, separate them by commas. Specifying
the option with no argument is the same as specifying
DEFAULT, and specifying with an explicit
value of "" disables recovery (same as not
giving the option). If recovery is enabled, each time
mysqld opens a MyISAM
table, it checks whether the table is marked as crashed or was
not closed properly. (The last option works only if you are
running with external locking disabled.) If this is the case,
mysqld runs a check on the table. If the
table was corrupted, mysqld attempts to
repair it.
The following options affect how the repair works.
| Option | Description |
|---|---|
DEFAULT | Recovery without backup, forcing, or quick checking. |
BACKUP | If the data file was changed during recovery, save a backup of the
file as
. |
FORCE | Run recovery even if we would lose more than one row from the
.MYD file. |
QUICK | Do not check the rows in the table if there are not any delete blocks. |
Before the server automatically repairs a table, it writes a
note about the repair to the error log. If you want to be able
to recover from most problems without user intervention, you
should use the options BACKUP,FORCE. This
forces a repair of a table even if some rows would be deleted,
but it keeps the old data file as a backup so that you can
later examine what happened.
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --old-style-user-limits | ||
| Option-File Format | old-style-user-limits | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Enable old-style user limits. (Before MySQL 5.0.3, account
resource limits were counted separately for each host from
which a user connected rather than per account row in the
user table.) See
Section 6.3.4, “Setting Account Resource Limits”. This option was added in
MySQL 5.0.3.
| Command-Line Format | --one-thread | ||
| Option-File Format | one-thread | ||
Only use one thread (for debugging under Linux). This option is available only if the server is built with debugging enabled. See MySQL Internals: Porting to Other Systems.
| Command-Line Format | --open-files-limit=# | ||
| Option-File Format | open-files-limit | ||
| Option Sets Variable | Yes, open_files_limit | ||
| Variable Name | open_files_limit | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
Changes the number of file descriptors available to
mysqld. You should try increasing the value
of this option if mysqld gives you the
error Too many open files.
mysqld uses the option value to reserve
descriptors with setrlimit(). If the
requested number of file descriptors cannot be allocated,
mysqld writes a warning to the error log.
mysqld may attempt to allocate more than
the requested number of descriptors (if they are available),
using the values of
max_connections and
table_cache to estimate
whether more descriptors will be needed.
On Unix, the value cannot be set less than ulimit -n.
| Command-Line Format | --pid-file=file_name | ||
| Option-File Format | pid-file=file_name | ||
| Option Sets Variable | Yes, pid_file | ||
| Variable Name | pid_file | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
The path name of the process ID file. The server creates the file in the data directory unless an absolute path name is given to specify a different directory. This file is used by other programs such as mysqld_safe to determine the server's process ID.
--port=,
port_num-P
port_num
| Command-Line Format | --port=# | ||
-P | |||
| Option-File Format | port | ||
| Option Sets Variable | Yes, port | ||
| Variable Name | port | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 3306 | ||
| Range | 0 .. 65535 | ||
The port number to use when listening for TCP/IP connections.
The port number must be 1024 or higher unless the server is
started by the root system user.
| Version Introduced | 5.0.19 | ||
| Command-Line Format | --port-open-timeout=# | ||
| Option-File Format | port-open-timeout | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 0 | ||
On some systems, when the server is stopped, the TCP/IP port might not become available immediately. If the server is restarted quickly afterward, its attempt to reopen the port can fail. This option indicates how many seconds the server should wait for the TCP/IP port to become free if it cannot be opened. The default is not to wait. This option was added in MySQL 5.0.19.
| Command-Line Format | --remove [service_name] | ||
(Windows only) Remove a MySQL Windows service. The default
service name is MySQL if no
service_name value is given. For
more information, see Section 2.10.4.7, “Starting MySQL as a Windows Service”.
| Command-Line Format | --safe-mode | ||
| Option-File Format | safe-mode | ||
| Deprecated | 5.5.26 | ||
Skip some optimization stages. This option is deprecated and is removed in MySQL 5.6.
| Command-Line Format | --safe-show-database | (until 4.1.1) | |
| Option-File Format | safe-show-database | ||
| Variable Name | safe_show_database | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Deprecated | 4.0.2 | ||
| Permitted Values | |||
| Type | boolean | ||
This option is deprecated and does not do anything because
there is a SHOW DATABASES
privilege that can be used to control access to database names
on a per-account basis. See
Section 6.2.1, “Privileges Provided by MySQL”.
--safe-show-database is removed
in MySQL 5.5.
| Command-Line Format | --safe-user-create | ||
| Option-File Format | safe-user-create | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
If this option is enabled, a user cannot create new MySQL
users by using the GRANT
statement unless the user has the
INSERT privilege for the
mysql.user table or any column in the
table. If you want a user to have the ability to create new
users that have those privileges that the user has the right
to grant, you should grant the user the following privilege:
GRANT INSERT(user) ON mysql.user TO 'user_name'@'host_name';
This ensures that the user cannot change any privilege columns
directly, but has to use the
GRANT statement to give
privileges to other users.
| Command-Line Format | --secure-auth | ||
| Option-File Format | secure-auth | ||
| Option Sets Variable | Yes, secure_auth | ||
| Variable Name | secure_auth | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
This option causes the server to block connections by clients that attempt to use accounts that have passwords stored in the old (pre-4.1) format. Use it to prevent all use of passwords employing the old format (and hence insecure communication over the network).
Server startup fails with an error if this option is enabled
and the privilege tables are in pre-4.1 format. See
Section C.5.2.4, “Client does not support authentication protocol”.
The mysql client also has a
--secure-auth option, which
prevents connections to a server if the server requires a
password in old format for the client account.
| Version Introduced | 5.0.38 | ||
| Command-Line Format | --secure-file-priv=path | ||
| Option-File Format | secure-file-priv=path | ||
| Option Sets Variable | Yes, secure_file_priv | ||
| Variable Name | secure-file-priv | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | string | ||
This option limits the effect of the
LOAD_FILE() function and the
LOAD DATA and
SELECT ... INTO
OUTFILE statements to work only with files in the
specified directory.
This option was added in MySQL 5.0.38.
| Variable Name | shared_memory | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Platform Specific | windows | ||
Enable shared-memory connections by local clients. This option is available only on Windows.
--shared-memory-base-name=
name
| Variable Name | shared_memory_base_name | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Platform Specific | windows | ||
The name of shared memory to use for shared-memory
connections. This option is available only on Windows. The
default name is MYSQL. The name is case
sensitive.
Disable the BDB storage engine. This saves
memory and might speed up some operations. Do not use this
option if you require BDB tables.
Turn off the ability to select and insert at the same time on
MyISAM tables. (This is to be used only if
you think you have found a bug in this feature.) See
Section 8.7.3, “Concurrent Inserts”.
Do not use external locking (system locking). This affects
only MyISAM table access. For
more information, including conditions under which it can and
cannot be used, see Section 8.7.4, “External Locking”.
External locking has been disabled by default since MySQL 4.0.
This option causes the server to start without using the
privilege system at all, which gives anyone with access to the
server unrestricted access to all
databases. You can cause a running server to start
using the grant tables again by executing mysqladmin
flush-privileges or mysqladmin
reload command from a system shell, or by issuing a
MySQL FLUSH
PRIVILEGES statement after connecting to the server.
This option also suppresses loading of user-defined functions
(UDFs).
Note that FLUSH
PRIVILEGES might be executed implicitly by other
actions performed after startup. For example,
mysql_upgrade flushes the privileges during
the upgrade procedure.
This option is unavailable if MySQL was configured with the
--disable-grant-options
option. See Section 2.17.3, “MySQL Source-Configuration Options”.
Disable use of the internal host cache for faster name-to-IP resolution. In this case, the server performs a DNS lookup every time a client connects. See Section 8.9.8, “DNS Lookup Optimization and the Host Cache”.
Disable the InnoDB storage engine. In this
case, the server will not start if the default storage engine
is set to InnoDB. Use
--default-storage-engine to set
the default to some other engine if necessary.
Disable the MERGE storage engine. This
option was added in MySQL 5.0.24. It can be used if the
following behavior is undesirable: If a user has access to
MyISAM table t,
that user can create a MERGE table
m that accesses
t. However, if the user's
privileges on t are subsequently
revoked, the user can continue to access
t by doing so through
m.
Do not resolve host names when checking client connections.
Use only IP addresses. If you use this option, all
Host column values in the grant tables must
be IP addresses or localhost. See
Section 8.9.8, “DNS Lookup Optimization and the Host Cache”.
Do not listen for TCP/IP connections at all. All interaction with mysqld must be made using named pipes or shared memory (on Windows) or Unix socket files (on Unix). This option is highly recommended for systems where only local clients are permitted. See Section 8.9.8, “DNS Lookup Optimization and the Host Cache”.
Options that begin with --ssl
specify whether to permit clients to connect using SSL and
indicate where to find SSL keys and certificates. See
Section 6.3.6.4, “SSL Command Options”.
| Command-Line Format | --standalone | ||
| Option-File Format | standalone | ||
| Platform Specific | windows | ||
Instructs the MySQL server not to run as a service.
--symbolic-links,
--skip-symbolic-links
| Command-Line Format | --symbolic-links | ||
| Option-File Format | symbolic-links | ||
Enable or disable symbolic link support. This option has different effects on Windows and Unix:
On Windows, enabling symbolic links enables you to
establish a symbolic link to a database directory by
creating a
file that contains the path to the real directory. See
Section 8.9.6.3, “Using Symbolic Links for Databases on Windows”.
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
options of the CREATE TABLE
statement. If you delete or rename the table, the files
that its symbolic links point to also are deleted or
renamed. See Section 8.9.6.2, “Using Symbolic Links for MyISAM Tables on Unix”.
| Command-Line Format | --skip-safemalloc | ||
| Option-File Format | skip-safemalloc | ||
If MySQL is configured with
--with-debug=full, all MySQL
programs check for memory overruns during each memory
allocation and memory freeing operation. This checking is very
slow, so for the server you can avoid it when you do not need
it by using the
--skip-safemalloc option.
| Command-Line Format | --skip-show-database | ||
| Option-File Format | skip-show-database | ||
| Option Sets Variable | Yes, skip_show_database | ||
| Variable Name | skip_show_database | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
This option sets the
skip_show_database system
variable that controls who is permitted to use the
SHOW DATABASES statement. See
Section 5.1.4, “Server System Variables”.
| Command-Line Format | --skip-stack-trace | ||
| Option-File 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 MySQL Internals: Porting to Other Systems.
| Command-Line Format | --skip-thread-priority | ||
| Option-File Format | skip-thread-priority | ||
| Deprecated | 5.1.29 | ||
Disable using thread priorities for faster response time.
mysqld makes a large number of invalid
calls to thread scheduling routines on Linux. These calls do
not affect performance noticeably but may be a source of
“noise” for debugging tools. For example, they
can overwhelm other information of more interest in kernel
logs. To avoid these calls, start the server with the
--skip-thread-priority option.
| Command-Line Format | --socket=name | ||
| Option-File Format | socket | ||
| Option Sets Variable | Yes, socket | ||
| Variable Name | socket | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
| Default | /tmp/mysql.sock | ||
On Unix, this option specifies the Unix socket file to use
when listening for local connections. The default value is
/tmp/mysql.sock. If this option is given,
the server creates the file in the data directory unless an
absolute path name is given to specify a different directory.
On Windows, the option specifies the pipe name to use when
listening for local connections that use a named pipe. The
default value is MySQL (not case
sensitive).
--sql-mode=
value[,value[,value...]]
| Command-Line Format | --sql-mode=name | ||
| Option-File Format | sql-mode | ||
| Option Sets Variable | Yes, sql_mode | ||
| Variable Name | sql_mode | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
Set the SQL mode. See Section 5.1.7, “Server SQL Modes”.
| Version Introduced | 5.0.20 | ||
| Command-Line Format | --sysdate-is-now | ||
| Option-File Format | sysdate-is-now | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
As of MySQL 5.0.12, SYSDATE()
by default returns the time at which it executes, not the time
at which the statement in which it occurs begins executing.
This differs from the behavior of
NOW(). This option causes
SYSDATE() to be an alias for
NOW(). For information about
the implications for binary logging and replication, see the
description for SYSDATE() in
Section 12.7, “Date and Time Functions” and for SET
TIMESTAMP in
Section 5.1.4, “Server System Variables”.
This option was added in MySQL 5.0.20.
--tc-heuristic-recover={COMMIT|ROLLBACK}
| Version Introduced | 5.0.3 | ||
| Command-Line Format | --tc-heuristic-recover=name | ||
| Option-File Format | tc-heuristic-recover | ||
| Permitted Values | |||
| Type | enumeration | ||
| Valid Values | COMMIT | ||
RECOVER | |||
The type of decision to use in the heuristic recovery process. Currently, this option is unused. Added in MySQL 5.0.3.
| Command-Line Format | --temp-pool | ||
| Option-File Format | temp-pool | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | TRUE | ||
This option causes most temporary files created by the server to use a small set of names, rather than a unique name for each new file. This works around a problem in the Linux kernel dealing with creating many new files with different names. With the old behavior, Linux seems to “leak” memory, because it is being allocated to the directory entry cache rather than to the disk cache.
| Command-Line Format | --transaction-isolation=name | ||
| Option-File Format | transaction-isolation | ||
| Option Sets Variable | Yes, tx_isolation | ||
| Permitted Values | |||
| Type | enumeration | ||
| Valid Values | READ-UNCOMMITTED | ||
READ-COMMITTED | |||
REPEATABLE-READ | |||
SERIALIZABLE | |||
Sets the default transaction isolation level. The
level value can be
READ-UNCOMMITTED,
READ-COMMITTED,
REPEATABLE-READ, or
SERIALIZABLE. See
Section 13.3.6, “SET TRANSACTION Syntax”.
The default transaction isolation level can also be set at
runtime using the SET
TRANSACTION statement or by setting the
tx_isolation system variable.
--tmpdir=,
path-t
path
| Command-Line Format | --tmpdir=path | ||
-t | |||
| Option-File Format | tmpdir | ||
| Option Sets Variable | Yes, tmpdir | ||
| Variable Name | tmpdir | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
The path of the directory to use for creating temporary files.
It might be useful if your default /tmp
directory resides on a partition that is too small to hold
temporary tables. This option accepts several paths that are
used in round-robin fashion. Paths should be separated by
colon characters (“:”) on Unix
and semicolon characters (“;”)
on Windows, NetWare, and OS/2. If the MySQL server is acting
as a replication slave, you should not set
--tmpdir to point to a
directory on a memory-based file system or to a directory that
is cleared when the server host restarts. For more information
about the storage location of temporary files, see
Section C.5.4.4, “Where MySQL Stores Temporary Files”. A replication slave needs
some of its temporary files to survive a machine restart so
that it can replicate temporary tables or
LOAD DATA
INFILE operations. If files in the temporary file
directory are lost when the server restarts, replication
fails.
--user={,
user_name|user_id}-u
{
user_name|user_id}
| Command-Line Format | --user=name | ||
-u name | |||
| Option-File Format | user | ||
| Permitted Values | |||
| Type | string | ||
Run the mysqld server as the user having
the name user_name or the numeric
user ID user_id.
(“User” in this context refers to a system login
account, not a MySQL user listed in the grant tables.)
This option is mandatory when starting
mysqld as root. The
server changes its user ID during its startup sequence,
causing it to run as that particular user rather than as
root. See
Section 6.1.1, “Security Guidelines”.
To avoid a possible security hole where a user adds a
--user=root option to a
my.cnf file (thus causing the server to
run as root), mysqld
uses only the first --user
option specified and produces a warning if there are multiple
--user options. Options in
/etc/my.cnf and
$MYSQL_HOME/my.cnf are processed before
command-line options, so it is recommended that you put a
--user option in
/etc/my.cnf and specify a value other
than root. The option in
/etc/my.cnf is found before any other
--user options, which ensures
that the server runs as a user other than
root, and that a warning results if any
other --user option is found.
Use this option with the --help
option for detailed help.
--version, -V
| Variable Name | version | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
Display version information and exit.
You can assign a value to a server system variable by using 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.
Note that when you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.
If you want to restrict the maximum value to which a variable can
be set at runtime with
SET, you
can define this by using the
--maximum-
command-line option.
var_name=value
It is also possible to set variables by using
--set-variable=
or var_name=value-O
syntax. This syntax is deprecated.
var_name=value
You can change the values of most system variables for a running
server with the
SET
statement. See Section 13.7.4, “SET Syntax”.
Section 5.1.4, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. Section 8.9.2, “Tuning Server Parameters”, includes information on optimizing the server by tuning system variables.

User Comments
open_files_limit: If your mysql server process runs as mysql then the setrlimit will not raise higher then the calling safe_mysqld process. Thus relying on max_connections*5 does not work for a Linux ulimit. Use open_files_limit to go beyond 1024.
To get the server listening on all interfaces, use 0.0.0.0 as the bind address. i.e.:
--bind-address=0.0.0.0
OS: Ubuntu (Debian) deployments
Option: open-files-limit
It seems that the Debian upstart doesn't use the parameters defined at /etc/security/limits.conf, so when you launch mysql through the service command (and so, under upstart), it overrides those defined limits and uses the default 1024.
The solution is to modify the mysql.conf file that defines the upstart service, it is located at /etc/init/mysql.conf and add the following lines before the pre-start block:
# NB: Upstart scripts do not respect
# /etc/security/limits.conf, so the open-file limits
# settings need to be applied here.
limit nofile 32000 32000
limit nproc 32000 32000
References:
http://serverfault.com/questions/440878/changing-open-files-limit-in-mysql-5-5
http://askubuntu.com/questions/288471/cant-open-files-after-updating-server-what-changed
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