File with .CNF extension contains configuration data for MySQL database – information about character encoding, cache settings, buffer method settings and timeouts. File is saved as a plain text format, therefore it can be opened using any standard text editor. Contents of the file can be altered with purpose of tunning database for desired performance on given system configuration.

MySQL is a computer software for creating and managing relational databases distributed under open-source license. In Linux family of systems configuration files are stored in /etc/ directory with default name my.cnf. These config files can be edited manually or downloaded from the internet in form of premade templates.