Incorrect password when restarting a cluster

Hello Community

I am new in Postgresql, and I used a "one click graphic installer", and  installed on Ubuntu and I need some assistance:

I would like to be advised on what I need to do when restarting a cluster as I am getting a password error when I try to. These are the steps I took:

hombakazi(at)hombakazi-VirtualBox:~$ sudo -i
[sudo] password for hombakazi:
root(at)hombakazi-VirtualBox:~# su
root(at)hombakazi-VirtualBox:~# su - postgres
$ /opt/PostgreSQL/9.2/scripts/serverctl.sh restart
Please enter your password if requested.
[sudo] password for postgres:
Sorry, try again.

So I don't understand whats going on because I know my postgres password and I use it to login and its working but here I get this error. What is it that I am not doing right? or I need to do.?

 
Ngejane Hombakazi
0728178913