[Samba] how to add a linux box into a samba domain

[robert rottermann]

hi there,
I am trying to setup a test nework to learn the interaction of the diverse tools
in a smaba/windows network.
now it looks as if I do something wrong when adding a linux box into the domain.

I have a samba domain ROTTI.
It is running on server haydn.redcor.home

from windows I can log into this domain.

now I have a linux box I wanto to join to this domain.
this is its global section:
[global]
	workgroup = rotti
	security = user
    add machine script = /usr/sbin/useradd  -c Machine -d /var/lib/nobody -s
/bin/false %m$
	domain logons = No
	domain master = No
	netbios name = chrissy
	passdb backend = smbpasswd
    ;;;
    ;;; Options for winbind
    ;;;
	winbind uid = 20000-30000
	winbind gid = 20000-30000
	winbind use default domain = yes

	log level = 3
	idmap gid = 20000-30000
	idmap uid = 20000-30000
	usershare allow guests = No

now my questions:
net join produces the message:
"cannot join as standalone machine"
why ?
what do I have to change?

wbinfo -a robert%secret
plaintext password authentication failed
Could not authenticate user robert with plaintext password
challenge/response password authentication failed
error code was NT_STATUS_INVALID_HANDLE (0xc0000008)
error messsage was: Invalid handle
Could not authenticate user robert with challenge/response

what have I to do, that wbinfo authenticates against the domain?

thanks
robert