4.2.6 Using Option Files

Most MySQL programs can read startup options from option files (sometimes called configuration files). Option files provide a convenient way to specify commonly used options so that they need not be entered on the command line each time you run a program. For the MySQL server, MySQL provides a number of preconfigured option files.

To determine whether a program reads option files, invoke it with the --help option. (For mysqld, use --verbose and --help.) If the program reads option files, the help message indicates which files it looks for and which option groups it recognizes.


A MySQL program started with the --no-defaults option reads no option files.

Option files are plain text files, created using any text editor.

MySQL looks for option files in the order described in the following discussion and reads any that exist. If an option file you want to use does not exist, create it with a plain text editor.


Option files used with MySQL Cluster programs are covered in Section 17.3, “Configuration of MySQL Cluster NDB 6.1-7.1”.

On Windows, MySQL programs read startup options from the files shown in the following table, in the specified order (top files are read first, files read later take precedence).

Table 4.1 Option Files Read on Windows Systems

File NamePurpose
%PROGRAMDATA%\MySQL\MySQL Server 5.1\my.ini, %PROGRAMDATA%\MySQL\MySQL Server 5.1\my.cnfGlobal options
%WINDIR%\my.ini, %WINDIR%\my.cnfGlobal options
C:\my.ini, C:\my.cnfGlobal options
BASEDIR\my.ini, BASEDIR\my.cnfGlobal options
defaults-extra-fileThe file specified with --defaults-extra-file, if any

In the preceding table, %PROGRAMDATA% represents the file system directory that contains application data for all users on the host. This path defaults to C:\ProgramData on Microsoft Windows Vista and greater, and C:\Documents and Settings\All Users\Application Data on older versions of Microsoft Windows.

%WINDIR% represents the location of your Windows directory. This is commonly C:\WINDOWS. Use the following command to determine its exact location from the value of the WINDIR environment variable:

C:\> echo %WINDIR%

%APPDATA% represents the value of the Windows application data directory. Use the following command to determine its exact location from the value of the APPDATA environment variable:

C:\> echo %APPDATA%

BASEDIR represents the MySQL base installation directory. When MySQL 5.1 has been installed using the installation and configuration wizards, this is typically C:\PROGRAMDIR\MySQL\MySQL 5.1 Server where PROGRAMDIR represents the programs directory (usually Program Files on English-language versions of Windows). See Section, “Starting the MySQL Server Instance Config Wizard”.

On Unix and Unix-like systems, MySQL programs read startup options from the files shown in the following table, in the specified order (top files are read first, files read later take precedence).


On Unix platforms, MySQL ignores configuration files that are world-writable. This is intentional as a security measure.

Table 4.2 Option Files Read on Unix and Unix-Like Systems

File NamePurpose
/etc/my.cnfGlobal options
/etc/mysql/my.cnfGlobal options (as of MySQL 5.1.15)
SYSCONFDIR/my.cnfGlobal options
$MYSQL_HOME/my.cnfServer-specific options (server only)
defaults-extra-fileThe file specified with --defaults-extra-file, if any
~/.my.cnfUser-specific options

In the preceding table, ~ represents the current user's home directory (the value of $HOME).

SYSCONFDIR represents the directory specified with the --sysconfdir option to configure when MySQL was built. By default, this is the etc directory located under the compiled-in installation directory. This location is used as of MySQL 5.1.10. (From 5.1.10 to 5.1.22, it was read last, after ~/.my.cnf.)

MYSQL_HOME is an environment variable containing the path to the directory in which the server-specific my.cnf file resides. If MYSQL_HOME is not set and you start the server using the mysqld_safe program, mysqld_safe attempts to set MYSQL_HOME as follows:

In MySQL 5.1, use of DATADIR as the location for my.cnf is deprecated.

Typically, DATADIR is /usr/local/mysql/data for a binary installation or /usr/local/var for a source installation. This is the data directory location built in when MySQL was compiled, not the location specified with the --datadir option when mysqld starts. Use of --datadir at runtime has no effect on where the server looks for option files that it reads before processing any options.

If multiple instances of a given option are found, the last instance takes precedence, with one exception: For mysqld, the first instance of the --user option is used as a security precaution, to prevent a user specified in an option file from being overridden on the command line.

The following description of option file syntax applies to files that you edit manually. This excludes .mylogin.cnf, which is created using mysql_config_editor and is encrypted.

Any long option that may be given on the command line when running a MySQL program can be given in an option file as well. To get the list of available options for a program, run it with the --help option. (For mysqld, use --verbose and --help.)

The syntax for specifying options in an option file is similar to command-line syntax (see Section 4.2.4, “Using Options on the Command Line”). However, in an option file, you omit the leading two dashes from the option name and you specify only one option per line. For example, --quick and --host=localhost on the command line should be specified as quick and host=localhost on separate lines in an option file. To specify an option of the form --loose-opt_name in an option file, write it as loose-opt_name.

Empty lines in option files are ignored. Nonempty lines can take any of the following forms:

Leading and trailing spaces are automatically deleted from option names and values.

You can use the escape sequences \b, \t, \n, \r, \\, and \s in option values to represent the backspace, tab, newline, carriage return, backslash, and space characters. In option files, these escaping rules apply:

The preceding rules mean that a literal backslash can be given as \\, or as \ if it is not followed by a valid escape sequence character.

The rules for escape sequences in option files differ slightly from the rules for escape sequences in string literals in SQL statements. In the latter context, if x is not a valid escape sequence character, \x becomes x rather than \x. See Section 9.1.1, “String Literals”.

The escaping rules for option file values are especially pertinent for Windows path names, which use \ as a path name separator. A separator in a Windows path name must be written as \\ if it is followed by an escape sequence character. It can be written as \\ or \ if it is not. Alternatively, / may be used in Windows path names and will be treated as \. Suppose that you want to specify a base directory of C:\Program Files\MySQL\MySQL Server 5.1 in an option file. This can be done several ways. Some examples:

basedir="C:\Program Files\MySQL\MySQL Server 5.1"
basedir="C:\\Program Files\\MySQL\\MySQL Server 5.1"
basedir="C:/Program Files/MySQL/MySQL Server 5.1"

If an option group name is the same as a program name, options in the group apply specifically to that program. For example, the [mysqld] and [mysql] groups apply to the mysqld server and the mysql client program, respectively.

The [client] option group is read by all client programs (but not by mysqld). This enables you to specify options that apply to all clients. For example, [client] is the appropriate group to use to specify the password for connecting to the server. (But make sure that the option file is accessible only by yourself, so that other people cannot discover your password.) Be sure not to put an option in the [client] group unless it is recognized by all client programs that you use. Programs that do not understand the option quit after displaying an error message if you try to run them.

Here is a typical global option file:




Here is a typical user option file:

# The following password will be sent to all standard MySQL clients
password="my password"



To create option groups to be read only by mysqld servers from specific MySQL release series, use groups with names of [mysqld-5.0], [mysqld-5.1], and so forth. The following group indicates that the sql_mode setting should be used only by MySQL servers with 5.1.x version numbers:


It is possible to use !include directives in option files to include other option files and !includedir to search specific directories for option files. For example, to include the /home/mydir/myopt.cnf file, use the following directive:

!include /home/mydir/myopt.cnf

To search the /home/mydir directory and read option files found there, use this directive:

!includedir /home/mydir

MySQL makes no guarantee about the order in which option files in the directory will be read.


Any files to be found and included using the !includedir directive on Unix operating systems must have file names ending in .cnf. On Windows, this directive checks for files with the .ini or .cnf extension.

Write the contents of an included option file like any other option file. That is, it should contain groups of options, each preceded by a [group] line that indicates the program to which the options apply.

While an included file is being processed, only those options in groups that the current program is looking for are used. Other groups are ignored. Suppose that a my.cnf file contains this line:

!include /home/mydir/myopt.cnf

And suppose that /home/mydir/myopt.cnf looks like this:



If my.cnf is processed by mysqld, only the [mysqld] group in /home/mydir/myopt.cnf is used. If the file is processed by mysqladmin, only the [mysqladmin] group is used. If the file is processed by any other program, no options in /home/mydir/myopt.cnf are used.

The !includedir directive is processed similarly except that all option files in the named directory are read.