How to fix CR_CONNECTION_ERROR (2002): Can't connect to local MySQL server through socket in MySQL

# Check MySQL service status (systemd)
systemctl status mysql
# or
systemctl status mysqld

# Check for MySQL process
ps aux | grep mysql
ps aux | grep mysqld

# Check if MySQL is listening on socket
sudo netstat -lnp | grep mysql
sudo ss -lnp | grep mysql

# Try to start MySQL if not running
sudo systemctl start mysql
# or
sudo service mysql start

# Check MySQL error log
sudo tail -f /var/log/mysql/error.log
# or
sudo tail -f /var/log/mysqld.log

# Common locations for MySQL logs:
# /var/log/mysql/error.log
# /var/log/mysqld.log
# /var/lib/mysql/hostname.err

# Find MySQL socket file location from server configuration
mysql --help | grep "socket"
# or check MySQL configuration
sudo grep -r "socket" /etc/mysql/

# Common socket file locations:
# /tmp/mysql.sock
# /var/run/mysqld/mysqld.sock
# /var/lib/mysql/mysql.sock
# /run/mysqld/mysqld.sock

# Check if socket file exists
ls -la /tmp/mysql.sock
ls -la /var/run/mysqld/mysqld.sock

# Check permissions on socket file and directory
ls -la /var/run/mysqld/
stat /var/run/mysqld/mysqld.sock

# Socket file should be accessible to your user
# Typical permissions: srwxrwxrwx (socket, world readable/writable)

# Fix permissions if needed
sudo chmod 777 /var/run/mysqld/mysqld.sock
sudo chown mysql:mysql /var/run/mysqld/mysqld.sock

// PHP PDO example with socket
$dsn = "mysql:unix_socket=/var/run/mysqld/mysqld.sock;dbname=mydatabase";
$pdo = new PDO($dsn, $username, $password);

// PHP mysqli example
$mysqli = new mysqli("localhost", $user, $password, $database, null, "/var/run/mysqld/mysqld.sock");

// In php.ini
mysql.default_socket = /var/run/mysqld/mysqld.sock
mysqli.default_socket = /var/run/mysqld/mysqld.sock
pdo_mysql.default_socket = /var/run/mysqld/mysqld.sock

# Python MySQL connector
import mysql.connector

config = {
    'user': 'username',
    'password': 'password',
    'database': 'mydb',
    'unix_socket': '/var/run/mysqld/mysqld.sock'
}

connection = mysql.connector.connect(**config)

// Node.js with mysql2
const mysql = require('mysql2/promise');

const connection = await mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'password',
  database: 'mydb',
  socketPath: '/var/run/mysqld/mysqld.sock'
});

# MySQL command line - use TCP/IP instead of socket
mysql -h 127.0.0.1 -P 3306 -u username -p

# Force TCP/IP with --protocol flag
mysql --protocol=tcp -u username -p

// PHP - TCP/IP connection
$dsn = "mysql:host=127.0.0.1;port=3306;dbname=mydatabase";
$pdo = new PDO($dsn, $username, $password);

# Python - TCP/IP
import mysql.connector

config = {
    'host': '127.0.0.1',
    'port': 3306,
    'user': 'username',
    'password': 'password',
    'database': 'mydb'
}

connection = mysql.connector.connect(**config)

-- Check MySQL bind address
SHOW VARIABLES LIKE 'bind_address';

-- Should be '*' or '0.0.0.0' or '127.0.0.1' for local TCP/IP
-- In my.cnf:
[mysqld]
bind-address = 0.0.0.0  # or 127.0.0.1 for local only
port = 3306

# Check current socket configuration
mysql -e "SHOW VARIABLES LIKE 'socket';"

# Common configuration files:
# /etc/mysql/my.cnf
# /etc/mysql/mysql.conf.d/mysqld.cnf
# /etc/my.cnf
# ~/.my.cnf

# Example socket configuration in my.cnf:
[mysqld]
socket = /var/run/mysqld/mysqld.sock

[client]
socket = /var/run/mysqld/mysqld.sock

[mysql]
socket = /var/run/mysqld/mysqld.sock

# Stop MySQL
sudo systemctl stop mysql

# Edit configuration
sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

# Add or modify socket line under [mysqld]
socket = /tmp/mysql.sock

# Also update [client] and [mysql] sections

# Restart MySQL
sudo systemctl start mysql

# Verify new socket file exists
ls -la /tmp/mysql.sock

# Check socket file ownership and permissions
ls -la /var/run/mysqld/mysqld.sock
# Should be owned by mysql user and accessible

# Check directory permissions
ls -ld /var/run/mysqld/

# Check SELinux status
getenforce
sestatus

# If SELinux is enforcing, check for denials
sudo ausearch -m avc -ts recent | grep mysql
sudo grep mysql /var/log/audit/audit.log

# Temporarily disable SELinux to test (not recommended for production)
sudo setenforce 0

# Check AppArmor on Ubuntu/Debian
sudo aa-status | grep mysql

# Check if user has access to socket
sudo -u www-data ls -la /var/run/mysqld/mysqld.sock

# Common fixes:
sudo chmod 755 /var/run/mysqld
sudo chown mysql:mysql /var/run/mysqld/mysqld.sock
sudo chmod 777 /var/run/mysqld/mysqld.sock  # Less secure, but works

# Add user to mysql group
sudo usermod -a -G mysql $USER
# Log out and back in for group changes to take effect