Samba and User Acount Passwords

I believe Samba is configured like that by default, here are the relevant lines in smb.conf:

# "security = user" is always a good idea. This will require a Unix account
# in this server for every user accessing the server. See
# /usr/share/doc/samba-doc/htmldocs/Samba3-HOWTO/ServerType.html
# in the samba-doc package for details.
    security = user

...

# 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

More info on these options and more here. Hope that helps.

EDIT:

The first time you add a linux user (adduser) you need to add them to smbpasswd as well.

sudo smbpasswd -a <user>

when prompted for a password use the same password you used with adduser. After this the smb password should be updated automatically when you change the linux password with sudo passwd <user>