• add a samba user with a password

smbpasswd -a viki
password:
confirm password:

• delete root user from samba, if you cannot delete the user using smbpasswd -x root try this:

pdbedit -x -u root

-x to delete user
-u to say which user

test to see if the user exists: smbpasswd -x root with the error message:
Failed to find entry for user root. (src: https://bugzilla.samba.org/show_bug.cgi?id=9981)