MySQL: how to determine which config file is being used?

Question

Is there a command to determine which configuration file MySQL 5.0 is currently using?

Answer 1

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.

Answer 2

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.

Answer 3

Taken from the fantastic "High Performance MySQL" O'Reilly book:

$ which mysqld
/usr/sbin/mysqld

$ /usr/sbin/mysqld --verbose --help | grep -A 1 "Default options"
Default options are read from the following files in the given order:
/etc/mysql/my.cnf ~/.my.cnf /usr/etc/my.cnf