#<Mysql2::Error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)> code example

Example 1: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.s

> ln -s /var/lib/mysql/mysql.sock /tmp/mysql.sock
> 
> service mysql start or service mysql start

Example 2: can't connect to local mysql server through socket '/var/run/mysqld/mysqld.sock'

# this saved my ass
# first  you must perform a graceful shutdown of the server from the command line rather than powering off the server
shutdown -h now

# an additional method for getting it back up again when you run into this problem is to move mysql.sock

# to centos
mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql.sock.bak

# to ubuntu
mv /var/run/mysqld/mysqld.sock /var/run/mysqld/mysqld.sock.bak

# restart mysql
service mysqld start

Example 3: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

sudo apt-get install mysql-server