can't createdb with my new user

[della <ildella(at)gmail(dot)com>]

hi, I describe my steps:

1. installed postgresql 8.2 via apt-get (ubuntu gutsy)
2. # sudo -u postgres psql template1
3. template1=# CREATE ROLE kokomo WITH LOGIN CREATEDB PASSWORD
'kokomo';
4. template1=# \q
5. # createdb kokomo_dev -U kokomo -W

Here I receive:
createdb: could not connect to database postgres: FATAL:  Ident
authentication failed for user "kokomo"

So, given that I do not fail submitting the password for kokomo when
requested... what could be the problem? Have I to create a system user
for kokomo?
If I use pgadmin3 I see the kokomo user with it own encrypted password
and I can create the DB with kokomo as a owner. So what am I missing
in the command line?

Thanks for help.