pgsql initial superuser

Hello. this is my "first" time using pgsql, and I seem to be running to
a bit of a corner here :-)

I've understood how to add a superuser/database-user/user but I have no
user to begin with.

~# createuser superuser
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: FATAL:  user "root" does not exist
createuser: creation of user "superuser" failed

So I need someway to add a user so I can add others. I belive this is
done in the pg_hba.conf file, but so far I've been unlucky. I'm using
the debian distributed pg_hba.conf file set up for local access, and I
tried the following lines, each a complete failure:

pg_hba.conf
<snip>
local all root md5
#OR
#local all root ident
<snip>

Even with "createuser blabla -Uroot -W" and using the "ident" auth
method fails. What am I missing here?

Thank you for the support :-D