Hello people,
                    I am having a little problem while installing "dspace-1.5.1-release" while reading the installation procedure from the documents provided in the package itself i m supposed to create a dspace database owned by a dspace postgreSQL user by executing the following command.

<createuser -U postgres -d -A -P dspace>

 when i execute the following command i am asked for password 2 times..
after that a question pops asking me if i want this role to be able to create new roles. ( y/n) after my answering the question (i have tried both yes and no) it says..

<createuser: could not connect to databse postgres: FATAL: Ident authentication failed for user postgres>

 what am i supposed to do now..??
Help please..its urgent..