Determine which MySQL configuration file is being used

If you run mysql --verbose --help | less it will tell you about line 11 which .cnf files it will look for.

You can also do mysql --print-defaults to show you how the configuration values it will use. This can also be useful in identifying just which config file it is loading.

If you are on Linux, then start the 'mysqld' with strace, for eg strace ./mysqld.

Among all the other system calls, you will find something like:

stat64("/etc/my.cnf", 0xbfa3d7fc)       = -1 ENOENT (No such file or directory)
stat64("/etc/mysql/my.cnf", {st_mode=S_IFREG|0644, st_size=4227, ...}) = 0
open("/etc/mysql/my.cnf", O_RDONLY|O_LARGEFILE) = 3

So, as you can see..it lists the .cnf files, that it attempts to use and finally uses.

mysqld --help --verbose is dangerous. You can easily overwrite pidfile for running instance! use it with --pid-file=XYZ

Oh, and you can't really use it if you have more than 1 instance running. It will only show you default value.

Really good article about it:

How to find MySQL configuration file?

Just did a quick test on ubuntu:

• installed mysql-server, which created /etc/mysql/my.cnf

• mysqld --verbose --help | grep -A 1 "Default options"

110112 13:35:26 [Note] Plugin 'FEDERATED' is disabled.
Default options are read from the following files in the given order: /etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf

• created /etc/my.cnf and /usr/etc/my.cnf, each with a different port number

• restarted mysql - it was using the port number set in /usr/etc/my.cnf

Also meanwhile found the --defaults-file option to the mysqld. If you specify a config file there, only that one will be used, regardless of what is returned by /usr/sbin/mysqld --verbose --help | grep -A 1 "Default options"

Using MySQL Workbench it will be shown under "Server Status":

I installed mysql use brew install mysql

mysqld --verbose --help | less

And it shows:

On CentOS and MariaDB you will find the MariaDB Server configuration settings in: /etc/my.cnf.d/server.cnf