How can I get Samba to store credentials for printing to Windows printer shares?
I can connect to the Windows printer share with 
smbclient //server/printer -U username -W mydomainBut I can't use CUPS to print. I've used these formats:
smb://username:password@domain/server/share
smb://domain/server/share
smb://server/share
CUPS adds the printer with the PPD, no problem, but seems to strip out the username and password. 
/usr/local/etc/samba/private/secrets.tdb seems to be where these credentials should be stored.
The error I get is "Session setup failed: NT_STATUS_LOGON_FAILURE"
Here's my sanitized smb.conf:
[global]
# workgroup = NT-Domain-Name or Workgroup-Name, eg: MIDEARTH
   workgroup = mydomain
# server string is the equivalent of the NT Description field
   server string = Samba Server
# Security mode. Defines in which mode Samba will operate. Possible 
# values are share, user, server, domain and ads. Most people will want 
# user level security. See the Samba-HOWTO-Collection for details.
   security = user
# This option is important for security. It allows you to restrict
# connections to machines which are on your local network. The
# following example restricts access to two C class networks and
# the "loopback" interface. For more examples of the syntax see
# the smb.conf man page
;   hosts allow = 192.168.1. 192.168.2. 127.
# If you want to automatically load your printer list rather
# than setting them up individually then you'll need this
   load printers = yes
# you may wish to override the location of the printcap file
;   printcap name = /etc/printcap
# on SystemV system setting printcap name to lpstat should allow
# you to automatically obtain a printer list from the SystemV spool
# system
;   printcap name = lpstat
# It should not be necessary to specify the print system type unless
# it is non-standard. Currently supported print systems include
# bsd, cups, sysv, plp, lprng, aix, hpux, qnx
;   printing = cups
# Uncomment this if you want a guest account, you must add this to /etc/passwd
# otherwise the user "nobody" is used
;  guest account = pcguest
# this tells Samba to use a separate log file for each machine
# that connects
   log file = /usr/local/samba/var/log.%m
# Put a capping on the size of the log files (in Kb).
   max log size = 50
# Use password server option only with security = server
# The argument list may include:
#   password server = My_PDC_Name [My_BDC_Name] [My_Next_BDC_Name]
# or to auto-locate the domain controller/s
#   password server = *
;   password server = <NT-Server-Name>
# Use the realm option only with security = ads
# Specifies the Active Directory realm the host is part of
;   realm = MY_REALM
# Backend to store user information in. New installations should 
# use either tdbsam or ldapsam. smbpasswd is available for backwards 
# compatibility. tdbsam requires no further configuration.
   passdb backend = tdbsam
# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting.
# Note: Consider carefully the location in the configuration file of
#       this line.  The included file is read at that point.
;   include = /usr/local/samba/lib/smb.conf.%m
# Configure Samba to use multiple interfaces
# If you have multiple network interfaces then you must list them
# here. See the man page for details.
;   interfaces = 192.168.12.2/24 192.168.13.2/24 
# Browser Control Options:
# set local master to no if you don't want Samba to become a master
# browser on your network. Otherwise the normal election rules apply
;   local master = no
# OS Level determines the precedence of this server in master browser
# elections. The default value should be reasonable
;   os level = 33
# Domain Master specifies Samba to be the Domain Master Browser. This
# allows Samba to collate browse lists between subnets. Don't use this
# if you already have a Windows NT domain controller doing this job
;   domain master = yes 
# Preferred Master causes Samba to force a local browser election on startup
# and gives it a slightly higher chance of winning the election
;   preferred master = yes
# Enable this if you want Samba to be a domain logon server for 
# Windows95 workstations. 
;   domain logons = yes
# if you enable domain logons then you may want a per-machine or
# per user logon script
# run a specific logon batch file per workstation (machine)
;   logon script = %m.bat
# run a specific logon batch file per username
;   logon script = %U.bat
# Where to store roving profiles (only for Win95 and WinNT)
#        %L substitutes for this servers netbios name, %U is username
#        You must uncomment the [Profiles] share below
;   logon path = \\%L\Profiles\%U
# Windows Internet Name Serving Support Section:
# WINS Support - Tells the NMBD component of Samba to enable it's WINS Server
;   wins support = yes
# WINS Server - Tells the NMBD components of Samba to be a WINS Client
#	Note: Samba can be either a WINS Server, or a WINS Client, but NOT both
;   wins server = w.x.y.z
# WINS Proxy - Tells Samba to answer name resolution queries on
# behalf of a non WINS capable client, for this to work there must be
# at least one	WINS Server on the network. The default is NO.
;   wins proxy = yes
# DNS Proxy - tells Samba whether or not to try to resolve NetBIOS names
# via DNS nslookups. The default is NO.
   dns proxy = no 
# These scripts are used on a domain controller or stand-alone 
# machine to add or delete corresponding unix accounts
;  add user script = /usr/sbin/useradd %u
;  add group script = /usr/sbin/groupadd %g
;  add machine script = /usr/sbin/adduser -n -g machines -c Machine -d /dev/null -s /bin/false %u
;  delete user script = /usr/sbin/userdel %u
;  delete user from group script = /usr/sbin/deluser %u %g
;  delete group script = /usr/sbin/groupdel %g
#============================ Share Definitions ==============================
[homes]
   comment = Home Directories
   browseable = no
   writable = yes
# Un-comment the following and create the netlogon directory for Domain Logons
; [netlogon]
;   comment = Network Logon Service
;   path = /usr/local/samba/lib/netlogon
;   guest ok = yes
;   writable = no
;   share modes = no
# Un-comment the following to provide a specific roving profile share
# the default is to use the user's home directory
;[Profiles]
;    path = /usr/local/samba/profiles
;    browseable = no
;    guest ok = yes
# NOTE: If you have a BSD-style print system there is no need to 
# specifically define each individual printer
[printers]
   comment = All Printers
   path = /usr/spool/samba
   browseable = no
# Set public = yes to allow user 'guest account' to print
   guest ok = no
   writable = no
   printable = yes