Username and password for postgresql?

I have installed postgresql in ubuntu.

But i need to know the username and password for it?

开发者_StackOverflow社区If i have to set it, how do i do that?

Thanks!

You do not need to know postgresql's password.Because by default,postgresql trust local os users.So you can login postgresql without password:

psql -d db -U postgres

then you can change you password:

alter user postgres password 'password';

Did you check the Ubuntu-manual?