Learning MySQL

Search Order for Options Files

The MySQL server and client programs look for options files in the standard locations and read them in order; values from later files take precedence over earlier ones. Options specified on the command line override values from options files.

You can tell a MySQL program to ignore the default options files by telling it to read a specific file at a location given with the defaults-file option. For example, you can write:

$ mysql --defaults-file=path_to_options_file

If you’d like to use an options file alongside the default files, you can specify it using the defaults-extra-file option:

$ mysql --defaults-extra-file=path_to_local_options_file

Finally, you can prevent programs from reading in any options files by adding the no-defaults option:

$ mysql --no-defaults

On a Linux or Mac OS X system, the search order is /etc/my.cnf, then <MySQL_Directory>/my.cnf, defaults-extra-file, and finally ~/.my.cnf. Note that for security reasons, files that are world-writable are ignored. A generally appropriate permission setting is for the file owner (user) to be able to read and write the file, but for the group and others to be able to only read the file. You can set this level of access by opening a terminal window and typing:

$ chmod u=rw,g=r,o=r configuration_file

Note that if you’re trying to change the permissions of a file owned by the system root user, you’ll need to run the chmod command when logged in as the system root user, or prefix the command with ...