Winbind is targeted at organizations that have an existing NT-based domain infrastructure into which they wish to put UNIX workstations or servers. Winbind will allow these organizations to deploy UNIX workstations without having to maintain a separate account infrastructure. This greatly simplifies the administrative overhead of deploying UNIX workstations into an NT-based organization.

Another interesting way in which we expect Winbind to be used is as a central part of UNIX-based appliances. Appliances that provide file and print services to Microsoft-based networks will be able to use Winbind to provide seamless integration of the appliance into the domain.

The term foreign SID is often met with the reaction that it is not relevant to a particular environment. The following documents an interchange that took place on the Samba mailing list. It is a good example of the confusion often expressed regarding the use of winbind.

Fact: Winbind is needed to handle users who use workstations that are NOT part of the local domain.

Response: “Why? I've used Samba with workstations that are not part of my domains lots of times without using winbind. I thought winbind was for using Samba as a member server in a domain controlled by another Samba/Windows PDC.”

If the Samba server will be accessed from a domain other than the local Samba domain, or if there will be access from machines that are not local domain members, winbind will permit the allocation of UIDs and GIDs from the assigned pool that will keep the identity of the foreign user separate from users that are members of the Samba domain.

This means that winbind is eminently useful in cases where a single Samba PDC on a local network is combined with both domain member and domain non-member workstations. If winbind is not used, the user george on a Windows workstation that is not a domain member will be able to access the files of a user called george in the account database of the Samba server that is acting as a PDC. When winbind is used, the default condition is that the local user george will be treated as the account DOMAIN\george and the foreign (non-member of the domain) account will be treated as MACHINE\george because each has a different SID.

Over the last few years, efforts have been underway by various Samba Team members to implement various aspects of the Microsoft Remote Procedure Call (MSRPC) system. This system is used for most network-related operations between Windows NT machines, including remote management, user authentication, and print spooling. Although initially this work was done to aid the implementation of Primary Domain Controller (PDC) functionality in Samba, it has also yielded a body of code that can be used for other purposes.

Winbind uses various MSRPC calls to enumerate domain users and groups and to obtain detailed information about individual users or groups. Other MSRPC calls can be used to authenticate NT domain users and to change user passwords. By directly querying a Windows PDC for user and group information, Winbind maps the NT account information onto UNIX user and group names.

Since late 2001, Samba has gained the ability to interact with Microsoft Windows 2000 using its “native mode” protocols rather than the NT4 RPC services. Using LDAP and Kerberos, a domain member running Winbind can enumerate users and groups in exactly the same way as a Windows 200x client would, and in so doing provide a much more efficient and effective Winbind implementation.

The NSS is a feature that is present in many UNIX operating systems. It allows system information such as hostnames, mail aliases, and user information to be resolved from different sources. For example, a standalone UNIX workstation may resolve system information from a series of flat files stored on the local file system. A networked workstation may first attempt to resolve system information from local files, and then consult an NIS database for user information or a DNS server for hostname information.

The NSS application programming interface allows Winbind to present itself as a source of system information when resolving UNIX usernames and groups. Winbind uses this interface and information obtained from a Windows NT server using MSRPC calls to provide a new source of account enumeration. Using standard UNIX library calls, you can enumerate the users and groups on a UNIX machine running Winbind and see all users and groups in an NT domain plus any trusted domain as though they were local users and groups.

The primary control file for NSS is /etc/nsswitch.conf. When a UNIX application makes a request to do a lookup, the C library looks in /etc/nsswitch.conf for a line that matches the service type being requested; for example, the “passwd” service type is used when user or group names are looked up. This config line specifies which implementations of that service should be tried and in what order. If the passwd config line is:

passwd: files example

then the C library will first load a module called /lib/libnss_files.so followed by the module /lib/libnss_example.so. The C library will dynamically load each of these modules in turn and call resolver functions within the modules to try to resolve the request. Once the request is resolved, the C library returns the result to the application.

This NSS interface provides an easy way for Winbind to hook into the operating system. All that needs to be done is to put libnss_winbind.so in /lib/ then add “winbind” into /etc/nsswitch.conf at the appropriate place. The C library will then call Winbind to resolve user and group names.

PAMs provide a system for abstracting authentication and authorization technologies. With a PAM module, it is possible to specify different authentication methods for different system applications without having to recompile these applications. PAM is also useful for implementing a particular policy for authorization. For example, a system administrator may only allow console logins from users stored in the local password file but only allow users resolved from an NIS database to log in over the network.

Winbind uses the authentication management and password management PAM interface to integrate Windows NT users into a UNIX system. This allows Windows NT users to log in to a UNIX machine and be authenticated against a suitable PDC. These users can also change their passwords and have this change take effect directly on the PDC.

PAM is configured by providing control files in the directory /etc/pam.d/ for each of the services that require authentication. When an authentication request is made by an application, the PAM code in the C library looks up this control file to determine what modules to load to do the authentication check and in what order. This interface makes adding a new authentication service for Winbind very easy: simply copy the pam_winbind.so module to /lib/security/, and the PAM control files for relevant services are updated to allow authentication via Winbind. See the PAM documentation in PAM-Based Distributed Authentication, for more information.

When a user or group is created under Windows NT/200x, it is allocated a numerical relative identifier (RID). This is slightly different from UNIX, which has a range of numbers that are used to identify users and the same range used to identify groups. It is Winbind's job to convert RIDs to UNIX ID numbers and vice versa. When Winbind is configured, it is given part of the UNIX user ID space and a part of the UNIX group ID space in which to store Windows NT users and groups. If a Windows NT user is resolved for the first time, it is allocated the next UNIX ID from the range. The same process applies for Windows NT groups. Over time, Winbind will have mapped all Windows NT users and groups to UNIX user IDs and group IDs.

The results of this mapping are stored persistently in an ID mapping database held in a tdb database. This ensures that RIDs are mapped to UNIX IDs in a consistent way.

An active directory system can generate a lot of user and group name lookups. To reduce the network cost of these lookups, Winbind uses a caching scheme based on the SAM sequence number supplied by NT domain controllers. User or group information returned by a PDC is cached by Winbind along with a sequence number also returned by the PDC. This sequence number is incremented by Windows NT whenever any user or group information is modified. If a cached entry has expired, the sequence number is requested from the PDC and compared against the sequence number of the cached entry. If the sequence numbers do not match, then the cached information is discarded and up-to-date information is requested directly from the PDC.

This section describes the procedures used to get Winbind up and running. Winbind is capable of providing access and authentication control for Windows Domain users through an NT or Windows 200x PDC for regular services, such as telnet and ftp, as well for Samba services.

If you have a Samba configuration file that you are currently using, BACK IT UP! If your system already uses PAM, back up the /etc/pam.d directory contents! If you haven't already made a boot disk, MAKE ONE NOW!

Messing with the PAM configuration files can make it nearly impossible to log in to your machine. That's why you want to be able to boot back into your machine in single-user mode and restore your /etc/pam.d to the original state it was in if you get frustrated with the way things are going.

The latest version of Samba-3 includes a functioning winbindd daemon. Please refer to the main Samba Web page, or better yet, your closest Samba mirror site for instructions on downloading the source code.

To allow domain users the ability to access Samba shares and files, as well as potentially other services provided by your Samba machine, PAM must be set up properly on your machine. In order to compile the Winbind modules, you should have at least the PAM development libraries installed on your system. Please refer to the PAM Web site http://www.kernel.org/pub/linux/libs/pam/.

Before starting, it is probably best to kill off all the Samba-related daemons running on your server. Kill off all smbd, nmbd, and winbindd processes that may be running. To use PAM, make sure that you have the standard PAM package that supplies the /etc/pam.d directory structure, including the PAM modules that are used by PAM-aware services, several PAM libraries, and the /usr/doc and /usr/man entries for PAM. Winbind is built better in Samba if the pam-devel package is also installed. This package includes the header files needed to compile PAM-aware applications.

root# cp ../samba/source/nsswitch/libnss_winbind.so /lib

root# ln -s /usr/lib/libnss_winbind.so /usr/lib/libnss_winbind.so.1
root# ln -s /usr/lib/libnss_winbind.so /usr/lib/nss_winbind.so.1
root# ln -s /usr/lib/libnss_winbind.so /usr/lib/nss_winbind.so.2

passwd:     files winbind
shadow:     files 
group:      files winbind

root# /sbin/ldconfig -v | grep winbind

root#  crle -u -l /usr/lib:/usr/local/lib

root#  crle

Configuration file [version 4]: /var/ld/ld.config
  Default Library Path (ELF):   /lib:/usr/lib:/usr/local/lib
  Trusted Directories (ELF):    /lib/secure:/usr/lib/secure  (system default)

Command line:
  crle -c /var/ld/ld.config -l /lib:/usr/lib:/usr/local/lib

WINBIND:
        program = /usr/lib/security/WINBIND
        options = authonly

root# /usr/local/samba/bin/net rpc join -S PDC -U Administrator

root# /usr/local/samba/sbin/winbindd

root# /usr/local/samba/sbin/winbindd -B

root# ps -ae | grep winbindd

3025 ?        00:00:00 winbindd

root# /usr/local/samba/bin/wbinfo -u

CEO\Administrator
CEO\burdell
CEO\Guest
CEO\jt-ad
CEO\krbtgt
CEO\TsInternetUser

root# /usr/local/samba/bin/wbinfo -g
CEO\Domain Admins
CEO\Domain Users
CEO\Domain Guests
CEO\Domain Computers
CEO\Domain Controllers
CEO\Cert Publishers
CEO\Schema Admins
CEO\Enterprise Admins
CEO\Group Policy Creator Owners

root# getent passwd

root# getent group

start() {
        KIND="SMB"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/bin/smbd $SMBDOPTIONS
        RETVAL=$?
        echo
        KIND="NMB"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/bin/nmbd $NMBDOPTIONS
        RETVAL2=$?
        echo
        KIND="Winbind"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/sbin/winbindd
        RETVAL3=$?
        echo
        [ $RETVAL -eq 0 -a $RETVAL2 -eq 0 -a $RETVAL3 -eq 0 ] && \
		touch /var/lock/subsys/smb || RETVAL=1
        return $RETVAL
}

        daemon /usr/local/samba/sbin/winbindd

        daemon /usr/local/samba/sbin/winbindd -B

stop() {
        KIND="SMB"
        echo -n $"Shutting down $KIND services: "
        killproc smbd
        RETVAL=$?
        echo
        KIND="NMB"
        echo -n $"Shutting down $KIND services: "
        killproc nmbd
        RETVAL2=$?
        echo
        KIND="Winbind"
        echo -n $"Shutting down $KIND services: "
        killproc winbindd
        RETVAL3=$?
        [ $RETVAL -eq 0 -a $RETVAL2 -eq 0 -a $RETVAL3 -eq 0 ] && \
		 rm -f /var/lock/subsys/smb
        echo ""
        return $RETVAL
}

	##
	## samba.server
	##

	if [ ! -d /usr/bin ]
	then                    # /usr not mounted
		exit
	fi

	killproc() {            # kill the named process(es)
		pid=`/usr/bin/ps -e |
		     /usr/bin/grep -w $1 |
		     /usr/bin/sed -e 's/^  *//' -e 's/ .*//'`
		[ "$pid" != "" ] && kill $pid
	}
	 
	# Start/stop processes required for Samba server

	case "$1" in

	'start')
	#
	# Edit these lines to suit your installation (paths, workgroup, host)
	#
	echo Starting SMBD
	   /usr/local/samba/bin/smbd -D -s \
		/usr/local/samba/smb.conf

	echo Starting NMBD
	   /usr/local/samba/bin/nmbd -D -l \
		/usr/local/samba/var/log -s /usr/local/samba/smb.conf

	echo Starting Winbind Daemon
	   /usr/local/samba/sbin/winbindd
	   ;;

	'stop')
	   killproc nmbd
	   killproc smbd
	   killproc winbindd
	   ;;

	*)
	   echo "Usage: /etc/init.d/samba.server { start | stop }"
	   ;;
	esac

/usr/local/samba/sbin/winbindd

/usr/local/samba/sbin/winbindd -B

root# make nsswitch/pam_winbind.so

root# cp ../samba/source/nsswitch/pam_winbind.so /lib/security

auth    required  /lib/security/pam_stack.so service=system-auth
account required  /lib/security/pam_stack.so service=system-auth

	enable = no

	enable = yes

auth       required     /lib/security/pam_listfile.so item=user sense=deny \
	 file=/etc/ftpusers onerr=succeed
auth       sufficient   /lib/security/pam_winbind.so
auth       required     /lib/security/pam_stack.so service=system-auth
auth       required     /lib/security/pam_shells.so
account    sufficient   /lib/security/pam_winbind.so
account    required     /lib/security/pam_stack.so service=system-auth
session    required     /lib/security/pam_stack.so service=system-auth

auth       required     /lib/security/pam_securetty.so
auth       sufficient   /lib/security/pam_winbind.so
auth       sufficient   /lib/security/pam_unix.so use_first_pass
auth       required     /lib/security/pam_stack.so service=system-auth
auth       required     /lib/security/pam_nologin.so
account    sufficient   /lib/security/pam_winbind.so
account    required     /lib/security/pam_stack.so service=system-auth
password   required     /lib/security/pam_stack.so service=system-auth
session    required     /lib/security/pam_stack.so service=system-auth
session    optional     /lib/security/pam_console.so

auth sufficient /lib/security/pam_winbind.so

required pam_securetty.so

sufficient /lib/security/pam_unix.so use_first_pass

#
#ident "@(#)pam.conf 1.14 99/09/16 SMI"
#
# Copyright (c) 1996-1999, Sun Microsystems, Inc.
# All Rights Reserved.
#
# PAM configuration
#
# Authentication management
#
login   auth required   /usr/lib/security/pam_winbind.so
login auth required  /usr/lib/security/$ISA/pam_unix.so.1 try_first_pass 
login auth required  /usr/lib/security/$ISA/pam_dial_auth.so.1 try_first_pass 
#
rlogin  auth sufficient /usr/lib/security/pam_winbind.so
rlogin  auth sufficient /usr/lib/security/$ISA/pam_rhosts_auth.so.1
rlogin auth required  /usr/lib/security/$ISA/pam_unix.so.1 try_first_pass
#
dtlogin auth sufficient /usr/lib/security/pam_winbind.so
dtlogin auth required  /usr/lib/security/$ISA/pam_unix.so.1 try_first_pass
#
rsh auth required /usr/lib/security/$ISA/pam_rhosts_auth.so.1
other   auth sufficient /usr/lib/security/pam_winbind.so
other auth required /usr/lib/security/$ISA/pam_unix.so.1 try_first_pass
#
# Account management
#
login   account sufficient      /usr/lib/security/pam_winbind.so
login account requisite /usr/lib/security/$ISA/pam_roles.so.1 
login account required /usr/lib/security/$ISA/pam_unix.so.1 
#
dtlogin account sufficient      /usr/lib/security/pam_winbind.so
dtlogin account requisite /usr/lib/security/$ISA/pam_roles.so.1 
dtlogin account required /usr/lib/security/$ISA/pam_unix.so.1 
#
other   account sufficient      /usr/lib/security/pam_winbind.so
other account requisite /usr/lib/security/$ISA/pam_roles.so.1 
other account required /usr/lib/security/$ISA/pam_unix.so.1 
#
# Session management
#
other session required /usr/lib/security/$ISA/pam_unix.so.1 
#
# Password management
#
#other   password sufficient     /usr/lib/security/pam_winbind.so
other password required /usr/lib/security/$ISA/pam_unix.so.1 
dtsession auth required /usr/lib/security/$ISA/pam_unix.so.1
#
# Support for Kerberos V5 authentication (uncomment to use Kerberos)
#
#rlogin auth optional /usr/lib/security/$ISA/pam_krb5.so.1 try_first_pass
#login auth optional /usr/lib/security/$ISA/pam_krb5.so.1 try_first_pass
#dtlogin auth optional /usr/lib/security/$ISA/pam_krb5.so.1 try_first_pass
#other auth optional /usr/lib/security/$ISA/pam_krb5.so.1 try_first_pass
#dtlogin account optional /usr/lib/security/$ISA/pam_krb5.so.1
#other account optional /usr/lib/security/$ISA/pam_krb5.so.1
#other session optional /usr/lib/security/$ISA/pam_krb5.so.1
#other password optional /usr/lib/security/$ISA/pam_krb5.so.1 try_first_pass

If nscd is running on the UNIX/Linux system, then even though NSSWITCH is correctly configured, it will not be possible to resolve domain users and groups for file and directory controls.

“ My smb.conf file is correctly configured. I have specified idmap uid = 12000, and idmap gid = 3000-3500 and winbind is running. When I do the following, it all works fine. ”

root# wbinfo -u
MIDEARTH\maryo
MIDEARTH\jackb
MIDEARTH\ameds
...
MIDEARTH\root

root# wbinfo -g
MIDEARTH\Domain Users
MIDEARTH\Domain Admins
MIDEARTH\Domain Guests
...
MIDEARTH\Accounts

root# getent passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/bin/bash
...
maryo:x:15000:15003:Mary Orville:/home/MIDEARTH/maryo:/bin/false

“ But the following command just fails: ”

root# chown maryo a_file
chown: `maryo': invalid user

“ This is driving me nuts! What can be wrong? ”

Same problem as the one above. Your system is likely running nscd, the name service caching daemon. Shut it down, do not restart it! You will find your problem resolved.