Can't connect to local MySQL server error.

A MySQL client can connect to the mysqld server in two different ways: Unix sockets, which connects trough a file in the file system, (default `/tmp/mysqld.sock'), or TCP/IP which connects trough a port number. Unix sockets are faster than TCP/IP but can only be used when connection to a server on the same computer. Unix sockets are used if one doesn't specify a hostname or if one specifies the special hostname 'localhost'.

Here follows some reasons to the error Can't connect to local MySQL server.

• You don't have a mysqld running. Check that you have a process named 'mysqld' running with ps. You can check the server by trying these different connections: (the port and socket may of course be different in your setup).

  mysqladmin version
  mysqladmin -h `hostname` version
  mysqladmin -h `hostname` --port=3306 version
  mysqladmin --socket=/tmp/mysql.sock version
  

• You are running on a system that uses mit-threads. Mit threads doesn't support sockets. If you are running on a system that doesn't have native threads mysqld uses the mit-thread package. See section Which operating systems does MySQL support?. When using MIT threads you must always give the hostname when connecting to the server. Try using 'mysqladmin -u `hostname` version to check the connection to the server.
• Someone has removed the unix socket mysqld uses. You may have a cron job that removes the mysql socket (default `/tmp/mysqld.sock'). You can always run mysqladmin version and check that the socket mysqladmin is trying to use really exists. The fix in this case is to change the cron job not to remove mysqld.sock or to place the socket somewhere else. You can move the socket by reconfiguring mysqld with ./configure --with-unix-socket-path=/my-own-place/mysql.sock or starting safe_mysqld with --socket=/my_own_place/mysqld.sock and setting the environment variable MYSQL_UNIX_PORT to point at the socket before starting your mysql clients.
• You have started the mysqld server with --socket=.... If you change the socket you must also notify the clients about the new path. You can do this by setting the environment variable MYSQL_UNIX_PORT to point at the socket or provide the socket as a argument to the mysql clients. You can for example test the socket with mysqladmin --socket=/path-to-socket version.

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