O manual em Conectando-se ao servidor MySQL sugere o uso da seguinte sintaxe:
shell> mysql --host=127.0.0.1
A explicação é:
On Unix, MySQL programs treat the host
name localhost specially, in a way
that is likely different from what you
expect compared to other network-based
programs. For connections to
localhost, MySQL programs attempt to
connect to the local server by using a
Unix socket file. This occurs even if
a --port or -P option is given to
specify a port number. To ensure that
the client makes a TCP/IP connection
to the local server, use --host or -h
to specify a host name value of
127.0.0.1, or the IP address or name of the local server. You can also
specify the connection protocol
explicitly, even for localhost, by
using the --protocol=TCP option. For
example: