List Samba users?
Solution 1:
I believe the command your looking for is pdbedit.
From the man page "pdbedit - manage the SAM database (Database of Samba Users)"
sudo pdbedit -L -v
-L to list users. -v to be verbose.
Solution 2:
In Samba 4 and later, there's also samba-tool user list and other useful user management commands