Mysql – After system reboot can’t connect to thesql

If you are having problems connecting through socket, you may try connecting to your mysql server via tcp:

mysql -h localhost

Or using username/password:

mysql -h localhost -u root -p

Either one may work depending on how the users are set up. If you get this error it means that the mysql command is at least talking to the server:

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

This sounds like maybe connections aren't being cleaned up in a timely manner. "show processlist" should show the connections if that's the case. Looking at the MySQL documentation, it appears this may be common with PHP unless certain PHP parameters are tweaked. You may want to look through the article and comments at http://dev.mysql.com/doc/refman/5.0/en/too-many-connections.html

Another possibility brought up by the very slow TCP connections is perhaps MySQL (or tcpwrappers) is trying to do hostname lookup for access and the lookup is slow. This seems unlikely when using unix sockets, but in case it's trying to match localhost or system hostnames it may be worth looking into whether any access rules could be moved to IP or removed.