I installed samba on my server and I am trying to write a script to spare me the two steps to add user, e.g.:

adduser username
smbpasswd -a username

My smb.conf states:

# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
   unix password sync = yes

Further reading brought me to pdbedit man page which states:

   -a     This option is used to add a user into the database.  This  com-
          mand needs a user name specified with the -u switch. When adding
          a new user, pdbedit will also ask for the password to be used.

          Example: pdbedit -a -u sorce
          new password:
          retype new password

          Note

          pdbedit does not call the unix password syncronisation script if
          unix password sync has been set. It only updates the data in the
          Samba user database.

          If you wish to add a user and synchronise the password that  im-
          mediately, use smbpasswd’s -a option.

So... now I decided to try adding a user with smbpasswd:

1st try, unix user still does not exist:

root@raspberrypi:/home/pi# smbpasswd -a newuser
New SMB password:
Retype new SMB password:
Failed to add entry for user newuser.

2nd try, unix user exists:

root@raspberrypi:/home/pi# useradd mag
root@raspberrypi:/home/pi# smbpasswd -a mag
New SMB password:
Retype new SMB password:
Added user mag.
# switch to user pi, and try to switch to mag
root@raspberrypi:/home/pi# su pi
pi@raspberrypi ~ $ su mag
Password: 
su: Authentication failure

So, now I am asking myself:

1. how do I make samba passwords sync with unix passwords?
2. where are samba passwords stored?

Can someone help enlighten me?