As of MySQL 5.6.8, on Unix platforms, mysql_install_db creates a default option file named my.cnf in the base installation directory. This file is created from a template included in the distribution package named my-default.cnf. You can find the template in or under the base installation directory. When started using mysqld_safe, the server uses my.cnf file by default. If my.cnf already exists, mysql_install_db assumes it to be in use and writes a new file named my-new.cnf instead.

With one exception, the settings in the default option file are commented and have no effect. The exception is that the file changes the sql_mode system variable from its default of NO_ENGINE_SUBSTITUTION to also include STRICT_TRANS_TABLES:

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

This setting produces a server configuration that results in errors rather than warnings for bad data in operations that modify transactional tables. See Section 5.1.8, “Server SQL Modes”.

The my-default.cnf template replaces the older sample option files formerly supplied with MySQL distributions (my-small.cnf, my-medium.cnf, my-large.cnf, and my-huge.cnf). As of MySQL 5.6.8, these older files are no longer distributed.

On Windows, MySQL Installer interacts with the user and creates a file named my.ini in the base installation directory as the default option file. If you install on Windows from a Zip archive, you can copy the my-default.ini template file in the base installation directory to my.ini and use the latter as the default option file.

On any platform, after completing the installation process, you can edit the default option file at any time to modify the parameters used by the server. For example, to use a parameter setting in the file that is commented with a # character at the beginning of the line, remove the #, and modify the parameter value if necessary. To disable a To disable a setting, either add a # to the beginning of the line or remove it.

For additional information about option file format and syntax, see Section 4.2.6, “Using Option Files”.

Before MySQL 5.6.8, MySQL distributions include several sample option files that can be used as a basis for tuning the MySQL server. Look for files named my-small.cnf, my-medium.cnf, my-large.cnf, and my-huge.cnf, which are sample files for small, medium, large, and very large systems. On Windows, the extension is .ini rather than .cnf.

For a binary distribution, look for the sample files in or under your installation directory. If you have a source distribution, look in the support-files directory. To use a sample file as a base configuration file, rename a copy of it and place the copy in the appropriate location. Regarding names and appropriate location, see the general information provided in Section 4.2.6, “Using Option Files”.