MySQL's configuration file my.cnf can reside in multiple locations depending on your installation and operating system. The common search paths MySQL checks (in order) are:

/etc/my.cnf
/etc/mysql/my.cnf
/usr/local/mysql/etc/my.cnf
~/.my.cnf

To determine which configuration file MySQL is actually using, execute:

mysql --help | grep "Default options" -A 1

Or from within MySQL client:

SHOW VARIABLES LIKE 'config_file';

If your /etc/my.cnf modifications aren't working, check these common issues:

1. File permissions: chmod 644 /etc/my.cnf
2. Correct section headers: [mysqld] for server settings
3. MySQL restart required: systemctl restart mysql

Here's a complete working example for UTF-8 configuration:

[mysqld]
collation-server = utf8_general_ci
character-set-server = utf8
init-connect = 'SET NAMES utf8'
skip-character-set-client-handshake = 1

[client]
default-character-set = utf8

[mysql]
default-character-set = utf8

Check loaded variables to verify changes:

SHOW VARIABLES LIKE 'character%';
SHOW VARIABLES LIKE 'collation%';

For more detailed debugging, start MySQL with:

mysqld --verbose --help

The MySQL configuration file my.cnf can exist in multiple locations depending on your installation method and operating system. Here are the most common paths to check:

/etc/my.cnf
/etc/mysql/my.cnf
/usr/local/mysql/etc/my.cnf
~/.my.cnf
/usr/etc/my.cnf

MySQL provides several ways to identify which configuration file it's actually using:

# Method 1: Using mysqld command
mysqld --help --verbose | grep -A 1 "Default options"

# Method 2: From running MySQL instance
mysqladmin variables | grep -i "config file"

# Method 3: Checking process information
ps aux | grep mysqld

MySQL follows a specific order when reading configuration files:

1. /etc/my.cnf
2. /etc/mysql/my.cnf
3. $MYSQL_HOME/my.cnf
4. ~/.my.cnf (user-specific)

Here's a complete example of a properly formatted UTF-8 configuration:

[mysqld]
# Character set configuration
collation-server = utf8_general_ci
character-set-server = utf8
default-character-set = utf8

# Performance tuning
innodb_buffer_pool_size = 1G
innodb_log_file_size = 256M
query_cache_size = 32M

If your changes aren't taking effect:

# Verify the file is being read
strace -e open mysqld 2>&1 | grep my.cnf

# Check for syntax errors
mysqld --validate-config

# Restart MySQL after changes
sudo systemctl restart mysql

For Homebrew installations on macOS:

# Typical path
/usr/local/etc/my.cnf

# Alternative locations
/usr/local/opt/mysql/my.cnf
/usr/local/Cellar/mysql/[version]/my.cnf

For Docker containers:

# The configuration is typically mounted
docker run -v /custom/my.cnf:/etc/mysql/my.cnf mysql:latest