When mysqld starts, various options can be used to alter the server’s behavior. Although you don’t need to know all of the server options available or use them—quite often the default settings are fine—as a database administrator, it’s useful to know what options exist for various categories that may be related to your needs.
Options may be given at the command line when starting or
restarting the server. However, it’s common practice to enter them
into a configuration file. On Unix-based systems, the main configuration file
typically is /etc/my.cnf. For Windows systems, the main file is usually either
c:\my.conf. Options are entered on separate lines
and follow a
variable=value format. Some
options are binary and can be enabled by just including the option at
the command line when starting the server or in the options file with
no value (or an equals sign followed by no value).
Within the options file, options are grouped under headings
contained within square brackets. The mysqld
daemon reads options from the configuration file under the headings of
[server] as it’s
started. For more recent versions of the MySQL server, the group
[mysqld-5.0] is also read. Groups are read in the
order mentioned here, and the last setting for an option read is the
one used. To get a list of options that mysqld is
using on a particular server, enter the following line from the
command line (results follow):
mysqld --print-defaults ...