Yesterday I got the error:

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

when I ran the command mysql through terminal in Ubuntu 10.10

This error can also be linked to error in phpmyadmin:

Connection for controluser as defined in your configuration failed.

I figured out it was due to mysqld not running. I simply did

sudo /etc/init.d/mysql start

to start mysql daemon. This solved the error.