I had a problem today, with the MySQL on one system claiming that:

Check that mysqld is running and that the socket: ‘/var/run/mysqld/mysqld.sock‘ exists!

After google-ing a little, I didn’t find a solution to solve my problem. But finally I solved the problem. Here is the solution:

1. Check the ownership and permisions of /var/run/mysqld/

# ls -l /var/run/ | grep mysqld

It must be of the user mysql, and the group root.

2. Make a backup of the my.cnf (as root) :

# sudo mv /etc/mysql/my.cnf /etc/mysql/my.cnf.back

3. Reconfigure Mysql-server:

# dpkg-reconfigure mysql-server-5.0

Provide the desired root password, and… There you go (of course you can edit the newly created my.cnf, to suit your needs).