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