MySQL Reference Manual for version 4.0.18.

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5.2.1 mysqld Command-line Options

When you start the mysqld server, you specify program options using any of the methods described in 4.3 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 the server uses the same options each time it runs. The best way to ensure this is to specify server options in an option file. See section 4.3.2 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 [xxxxx_SERVER] groups, where xxxxx is the name of the application into which the server is embedded.

mysqld accepts many command-line options. For a list, execute mysqld --help. Before MySQL 4.1.1, --help prints the full help message. As of 4.1.1, it prints a brief message; to see the full list, use mysqld --help --verbose.

The following list shows some of the most common server options. Options used for replication are listed in a separate section, see 6.7 Replication Startup Options.

--ansi
Use SQL-99 syntax instead of MySQL syntax. See section 1.8.3 Running MySQL in ANSI Mode. For more precise control over the server SQL mode, use the --sql-mode option instead.

--basedir=path, -b path
The path to the installation directory. All paths are usually resolved relative to this.

--big-tables
Allow large result sets by saving all temporary sets on file. This option prevents most "table full" errors, but also slows down queries for which in-memory tables would suffice. Since Version 3.23.2, MySQL is able to handle large result sets automatically by using memory for small temporary tables and switching to disk tables where necessary.

--bind-address=IP
The IP address to bind to.

--console
Write the error log messages to stderr/stdout even if --log-error is specified. On Windows, mysqld will not close the console screen if this option is used.

--character-sets-dir=path
The directory where character sets are installed. See section 5.7.1 The Character Set Used for Data and Sorting.

--chroot=path
Put the mysqld server in a closed environment during startup by using the chroot() system call. This is a recommended security measure as of MySQL 4.0. (MySQL 3.23 is not able to provide a chroot() jail that is 100% closed.) Note that use of this option somewhat limits LOAD DATA INFILE and SELECT ... INTO OUTFILE.

--core-file
Write a core file if mysqld dies. For some systems, you must also specify the --core-file-size option to mysqld_safe. See section mysqld_safe. Note that on some systems, such as Solaris, you will not get a core file if you are also using the --user option.

--datadir=path, -h path
The path to the data directory.

--debug[=...]
If MySQL is configured with --with-debug, you can use this option to get a trace file of what mysqld is doing. See section D.1.2 Creating Trace Files.

--default-character-set=charset
Set the default character set. See section 5.7.1 The Character Set Used for Data and Sorting.

--default-table-type=type
Set the default table type for tables. See section 14. MySQL Table Types.

--delay-key-write[= OFF | ON | ALL]
How the DELAYED KEYS option should be used. 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 DELAYED KEYS option. ALL delays key writes for all MyISAM tables. Available as of MySQL 4.0.3. See section 7.5.2 Tuning Server Parameters.

--delay-key-write-for-all-tables
Old form of --delay-key-write=ALL for use prior to MySQL 4.0.3. As of 4.0.3, use --delay-key-write instead.

--des-key-file=filename
Read the default keys used by DES_ENCRYPT() and DES_DECRYPT() from this file.

--enable-external-locking
Enable system locking. Note that if you use this option on a system on which lockd does not fully work (as on Linux), you will easily get mysqld to deadlock. This option used to be named --enable-locking.

--enable-named-pipe
Enable support for named pipes. This option applies only on Windows NT, 2000, and XP systems, and may be used only with the mysqld-nt and mysqld-max-nt servers that support named pipe connections.

--exit-info, -T
This is a bit mask of different flags you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!

--flush
Flush all changes to disk after each SQL statement. Normally MySQL only does a write of all changes to disk after each SQL statement and lets the operating system handle the syncing to disk. See section A.4.1 What To Do If MySQL Keeps Crashing.

--help, -?
Display a short help message and exit. Prior to MySQL 4.1.1, --help displays the full help message. As of 4.1.1, it displays an abbreviated message only. Use both the --verbose and --help options to see the full message.

--init-file=file
Read SQL statements from this file at startup.

--language=lang_name, -L lang_name
Client error messages in given language. lang_name may be given as the language name or as the full pathname to the directory where the language files are installed. See section 5.7.2 Non-English Error Messages.

--log[=file], -l [file]
Log connections and queries to this file. See section 5.8.2 The General Query Log. If you don't specify a file name, MySQL will use hostname.log as filename.

--log-bin=[file]
Log all queries that change data to this file. Used for backup and replication. See section 5.8.4 The Binary Log. If you don't specify a file name, MySQL will use hostname-bin as filename.

--log-bin-index[=file]
The index file for binary log file names. See section 5.8.4 The Binary Log. If you don't specify file name, MySQL will use hostname-bin.index as filename.

--log-error[=file]
Log errors and startup messages to this file. See section 5.8.1 The Error Log. If you don't specify file name, MySQL will use hostname.err as filename.

--log-isam[=file]
Log all ISAM/MyISAM changes to this file (used only when debugging ISAM/MyISAM).

--log-long-format
Log some extra information to the log files (update log, binary update log, and slow queries log, whatever log has been activated). For example, username and timestamp are logged for queries. If you are using --log-slow-queries and --log-long-format, then queries that are not using indexes also are logged to the slow query log. Note that --log-long-format is deprecated as of MySQL version 4.1, when --log-short-format was introduced (the long log format is the default setting since version 4.1). Also note that starting with MySQL 4.1 the --log-queries-not-using-indexes option is available for the purpose of logging queries that do not use indexes to the slow queries log.

--log-queries-not-using-indexes
If you are using this option with --log-slow-queries, then also queries that are not using indexes are logged to the slow query log. This option is available as of MySQL 4.1. See section 5.8.5 The Slow Query Log.

--log-short-format
Log less information to the log files (update log, binary update log, and slow queries log, whatever log has been activated). For example, username and timestamp are not logged for queries. This options was introduced in MySQL 4.1.

--log-slow-queries[=file]
Log all queries that have taken more than long_query_time seconds to execute to file. Note that the default for the amount of information logged has changed in MySQL 4.1. See the --log-long-format and --log-long-format options for details. See section 5.8.5 The Slow Query Log.

--log-update[=file]
Log updates to file.# where # is a unique number if not given. See section 5.8.3 The Update Log. The update log is deprecated and is removed in MySQL 5.0.0; you should use the binary log instead (--log-bin). See section 5.8.4 The Binary Log. Starting from version 5.0.0, using --log-update will just turn on the binlog instead (see section C.1.2 Changes in release 5.0.0 (22 Dec 2003: Alpha)).

--log-warnings, -W
Print out warnings like Aborted connection... to the `.err' file. Enabling this option is recommended, for example, if you use replication (you will get more information about what is happening, such as messages about network failures and reconnections). See section A.2.10 Communication Errors / Aborted Connection.

This option used to be called --warnings.

--low-priority-updates
Table-modifying operations (INSERT/DELETE/UPDATE) will have lower priority than selects. It can also be done via {INSERT | REPLACE | UPDATE | DELETE} LOW_PRIORITY ... to lower the priority of only one query, or by SET LOW_PRIORITY_UPDATES=1 to change the priority in one thread. See section 7.3.2 Table Locking Issues.

--memlock
Lock the mysqld process in memory. This works on systems such as Solaris that support the mlockall() system call. This may help if you have a problem where the operating system is causing mysqld to swap on disk. Note that use of this option requires that you run the server as root, which is normally not a good idea for security reasons.

--myisam-recover [=option[,option...]]]
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, seprate them by commas. You can also use a value of "" to disable this option. If this option is used, mysqld will on open check if the table is marked as crashed or if the table wasn't closed properly. (The last option works only if you are running with --skip-external-locking.) If this is the case mysqld will run check on the table. If the table was corrupted, mysqld will attempt to repair it.

The following options affects how the repair works.

--myisam-recover. backup of the `table_name.MYD' datafile as `table_name-datetime.BAK'. from the `.MYD' file. delete blocks.
Option Description
DEFAULT The same as not giving any option to
BACKUP If the data table was changed during recover, save a
FORCE Run recover even if we will lose more than one row
QUICK Don't check the rows in the table if there aren't any

Before a table is automatically repaired, MySQL will add a note about this in 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 will force a repair of a table even if some rows would be deleted, but it will keep the old datafile as a backup so that you can later examine what happened.

--new
From version 4.0.12, the --new option can be used to make the server behave as 4.1 in certain respects, easing a 4.0 to 4.1 upgrade:

This option can be used to help you see how your applications will behave in MySQL 4.1, without actually upgrading to 4.1.

--pid-file=path
The path to pid file used by mysqld_safe.

--port=num, -P num
The port number to listen for TCP/IP connections.

--old-protocol, -o
Use the 3.20 protocol for compatibility with some very old clients. See section 2.5.6 Upgrading from Version 3.20 to 3.21.

--one-thread
Only use one thread (for debugging under Linux). This option is available only if the server is built with debugging enabled. See section D.1 Debugging a MySQL server.

--open-files-limit=
To change the number of file descriptors available to mysqld. If this is not set or set to 0, then mysqld will use this value to reserve file descriptors to use with setrlimit(). If this value is 0 then mysqld will reserve max_connections*5 or max_connections + table_cache*2 (whichever is larger) number of files. You should try increasing this if mysqld gives you the error 'Too many open files'.

--set-variable=name=value, -O value
Assign a value to a system variable. Use --help to list the variables. You can find a full description for all variables in the SHOW VARIABLES section in this manual. See section SHOW VARIABLES. The section on tuning server parameters includes information on how to optimize them. See section 7.5.2 Tuning Server Parameters.

Please note that --set-variable=name=value and -O name=value syntax is deprecated as of MySQL 4.0.2. In 4.0.2, you can set variables directly using --variable-name=value syntax, and --set-variable is no longer needed.

If you want to restrict the maximum value a startup option can be set to with SET, you can define this by using the --maximum-variable-name command line option. See section SET OPTION.

Note that when setting a variable to a value, MySQL may automatically correct it to stay within a given range, or adjust the value to the closest allowable value if only certain values are allowed.

--safe-mode
Skip some optimize stages.

--safe-show-database
With this option, the SHOW DATABASES statement returns only those databases for which the user has some kind of privilege. From version 4.0.2 this option is deprecated and doesn't do anything (the option is enabled by default) as we now have the SHOW DATABASES privilege. See section GRANT.

--safe-user-create
If this is enabled, a user can't create new users with the GRANT statement, if the user doesn't have INSERT privilege to the mysql.user table or any column in this table.

--skip-bdb
Disable the BDB storage engine. This saves memory and may speed up some operations. Do not use this operation if you require BDB tables.

--skip-concurrent-insert
Turn off the ability to select and insert at the same time on MyISAM tables. (This is only to be used if you think you have found a bug in this feature.)

--skip-delay-key-write
Ignore the DELAY_KEY_WRITE option for all tables. As of MySQL 4.0.3, you should use --delay-key-write=OFF instead. See section 7.5.2 Tuning Server Parameters.

--skip-external-locking
Don't use system locking. To use isamchk or myisamchk you must shut down the server. See section 1.2.3 MySQL Stability. Note that in MySQL Version 3.23, you can use CHECK TABLE and REPAIR TABLE to check and repairMyISAM tables. This option used to be named --skip-locking.

--skip-grant-tables
This option causes the server not to use the privilege system at all. This gives everyone full access to all databases! (You can tell a running server to start using the grant tables again by executing a mysqladmin flush-privileges or mysqladmin reload command, or by issuing a FLUSH PRIVILEGES statement.)

--skip-host-cache
Do not use the internal hostname cache for faster name-IP resolution. Instead, query the DNS server every time a client connects. See section 7.5.5 How MySQL uses DNS.

--skip-innodb
Disable the InnoDB storage engine. This saves memory and disk space and may speed up some operations. Do not use this operation if you require InnoDB tables.

--skip-isam
Disable the ISAM storage engine. As of MySQL 4.1, ISAM is disabled by default, so this option applies only if the server was configured with support for ISAM. This option was added in MySQL 4.1.1.

--skip-name-resolve
Do not resolve hostnames when checking client connections. Use only IP numbers. If you use this option, all Host column values in the grant tables must be IP numbers or localhost. See section 7.5.5 How MySQL uses DNS.

--skip-networking
Don't listen for TCP/IP connections at all. All interaction with mysqld must be made via named pipes (on Windows) or Unix socket files (on Unix). This option is highly recommended for systems where only local clients are allowed. See section 7.5.5 How MySQL uses DNS.

--skip-new
Don't use new, possibly wrong routines.

--skip-symlink
This is the old form of --skip-symbolic-links, for use before MySQL 4.0.13.

--symbolic-links, --skip-symbolic-links
Enable or disable symbolic link support. This option has different effects on Windows and Unix:

This option was added in MySQL 4.0.13.

--skip-safemalloc
If MySQL is configured with --with-debug=full, all MySQL programs checks 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 don't need it by using the --skip-safemalloc option.

--skip-show-database
Don't allow the SHOW DATABASES statement, unless the user has the SHOW DATABASES privilege.

--skip-stack-trace
Don't 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 D.1 Debugging a MySQL server.

--skip-thread-priority
Disable using thread priorities for faster response time.

--socket=path
On Unix, this option specifies the Unix socket file to use for local connections. The default value is `/tmp/mysql.sock'. On Windows, the option specifies the pipe name to use for local connections that use a named pipe. The default value is MySQL.

--sql-mode=value[,value[,value...]]
Set the SQL mode for MySQL. See section 1.8.2 Selecting SQL Modes. This option was added in 3.23.41.

--temp-pool
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, as it's being allocated to the directory entry cache rather than to the disk cache.

--transaction-isolation=level
Sets the default transaction isolation level, which may be READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See section SET TRANSACTION.

--tmpdir=path, -t path
The path of the directory to use for creating temporary files. It may be useful if your default /tmp directory resides on a partition that is too small to hold temporary tables. Starting from MySQL 4.1, 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. It is possible to set tmpdir to point to a memory-based filesystem, except if the MySQL server is a slave replication server. If it is a slave, some of its temporary files are needed to survive a machine's reboot. (For example, to replicate temporary tables or LOAD DATA INFILE statements). In this case, a memory-based tmpdir that is cleared when the machine reboots is not suitable; a disk-based tmpdir is necessary.

--user={user_name | user_id}, -u {user_name | user_id}
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 will change its user ID during its startup sequence, causing it to run as that particular user rather than as root. See section 5.3.1 General Security Guidelines.

Starting from MySQL 3.23.56 and 4.0.12: To avoid a possible security hole where a user adds a --user=root option to some `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 `datadir/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' will be 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.

--version, -V
Display version information and exit.

You can change the values of most system variables for a running server with the SET statement. See section SET OPTION.


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