Postgresql doubt ..

[<shyamk@eth.net>]

[shyam@home shyam]$ xhost +
[shyam@home shyam]$ su postgres
bash $createdb shyamdb
psql.connectDBStart() ... connect() failed : Cannot respond
     Is the postmaster running at 'localhost' & accepting connection on Unix socket
'1234' ?
createdb : database creation failed.

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Dear members ,
   Can anybody please tell me what the above means , and how to circumvent it ?
   I am actually sitting on postgresql for the first time ,
and am startled .

Please help ...
(shyamk@eth.net)
Shyam