[Samba] simple question

[kent E.]

i just got confused in creating machine accounts in my samba server

1rst creating the user
[root at genesis root]# smbpasswd -a cpu3
New SMB password:
Retype new SMB password:
Added user cpu3.

than adding the machine...
[root at genesis root]# smbpasswd -a -m cpu3$
Failed initialise SAM_ACCOUNT for user cpu3$.
Failed to modify password entry for user cpu3$
[root at genesis root]#

what am i missing... (still googling...)

TIA
Kent