hi-problem in creating database in postgresql 7.2.2

hi
  i have sucessfully installed postgresql. now while creating database it
gives the following error. i'm running pgsqlserver on localhost.

 i give the command createdb -D /usr/local/share/data/data


  $ createdb -D /usr/local/share/data/data
psql: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
createdb: database creation failed

  similar problem is there when i create user.

$ createuser saurabh with password 'saurabh';
Shall the new user be allowed to create databases? (y/n) y
Shall the new user be allowed to create more new users? (y/n) y
psql: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
createuser: creation of user "saurabh" failed


 can u help me please? thnx in advance.


regards,


saurabh garg