winbindd (8)

Samba

13 Jun 2000

NAME

winbindd - Name Service Switch daemon for resolving names from NT servers

SYNOPSIS

DESCRIPTION

This program is part of the Samba suite version 3.0 and describes functionality not yet implemented in the main version of Samba.

winbindd is a daemon that provides a service for the Name Service Switch capability that is present in most modern C libraries. The Name Service Switch allows user and system information to be obtained from different databases services such as NIS or DNS. The exact behaviour can be configured throught the /etc/nsswitch.conf file. Users and groups are allocated as they are resolved to a range of user and group ids specified by the administrator of the Samba system.

The service provided by winbindd is called `winbind' and can be used to resolve user and group information from a Windows NT server. The service can also provide authentication services via an associated PAM module.

The following nsswitch databases are implemented by the winbindd service:

passwd

User information traditionally stored in the passwd(5) file and used by getpwent(3) functions.

group

Group information traditionally stored in the group(5) file and used by getgrent(3) functions.

For example, the following simple configuration in the /etc/nsswitch.conf file can be used to initially resolve user and group information from /etc/passwd and /etc/group and then from the Windows NT server.


  passwd:         files winbind
  group:          files winbind

OPTIONS

The following options are available to the winbindd daemon:

-d debuglevel

Sets the debuglevel to an integer between 0 and 100. 0 is for no debugging and 100 is for reams and reams. To submit a bug report to the Samba Team, use debug level 100 (see BUGS.txt).

-i

Tells winbindd to not become a daemon and detach from the current terminal. This option is used by developers when interactive debugging of winbindd is required.

NAME AND ID RESOLUTION

Users and groups on a Windows NT server are assigned a relative id (rid) which is unique for the domain when the user or group is created. To convert the Windows NT user or group into a unix user or group, a mapping between rids and unix user and group ids is required. This is one of the jobs that winbindd performs.

As winbindd users and groups are resolved from a server, user and group ids are allocated from a specified range. This is done on a first come, first served basis, although all existing users and groups will be mapped as soon as a client performs a user or group enumeration command. The allocated unix ids are stored in a database file under the Samba lock directory and will be remembered.

WARNING: The rid to unix id database is the only location where the user and group mappings are stored by winbindd. If this file is deleted or corrupted, there is no way for winbindd to determine which user and group ids correspond to Windows NT user and group rids.

CONFIGURATION

Configuration of the winbindd daemon is done through configuration parameters in the smb.conf file. All parameters should be specified in the [global] section of smb.conf.

winbind separator

The winbind separator option allows you to specify how NT domain names and user names are combined into unix user names when presented to users. By default winbind will use the traditional \ separator so that the unix user names look like DOMAIN\username. In some cases this separator character may cause problems as the \ character has special meaning in unix shells. In that case you can use the winbind separator option to specify an alternative sepataror character. Good alternatives may be / (although that conflicts with the unix directory separator) or a + character. The + character appears to be the best choice for 100% compatibility with existing unix utilities, but may be an aesthetically bad choice depending on your taste.

Default: winbind separator = \

Example: winbind separator = +

winbind uid

The winbind uid parameter specifies the range of user ids that are allocated by the winbindd daemon. This range of ids should have no existing local or nis users within it as strange conflicts can occur otherwise.

Default: winbind uid = <empty string>

Example: winbind uid = 10000-20000

winbind gid

The winbind gid parameter specifies the range of group ids that are allocated by the winbindd daemon. This range of group ids should have no existing local or nis groups within it as strange conflicts can occur otherwise.

Default: winbind gid = <empty string>

Example: winbind gid = 10000-20000

winbind cache time

This parameter specifies the number of seconds the winbindd daemon will cache user and group information before querying a Windows NT server again. When a item in the cache is older than this time winbindd will ask the domain controller for the sequence number of the servers account database. If the sequence number has not changed then the cached item is marked as valid for a further "winbind cache time" seconds. Otherwise the item is fetched from the server. This means that as long as the account database is not actively changing winbindd will only have to send one sequence number query packet every "winbind cache time" seconds.

Default: winbind cache time = 15

template homedir

When filling out the user information for a Windows NT user, the winbindd daemon uses this parameter to fill in the home directory for that user. If the string %D is present it is substituted with the user's Windows NT domain name. If the string %U is present it is substituted with the user's Windows NT user name.

Default: template homedir = /home/%D/%U

template shell

When filling out the user information for a Windows NT user, the winbindd daemon uses this parameter to fill in the shell for that user.

Default: template shell = /bin/false

EXAMPLE SETUP

To setup winbindd for user and group lookups plus authentication from a domain controller use something like the following setup. This was tested on a RedHat 6.2 Linux box.

In /etc/nsswitch.conf put the following:


   passwd:     files winbind
   group:      files winbind

In /etc/pam.d/* replace the auth lines with something like this:


	auth       required	/lib/security/pam_securetty.so
	auth       required	/lib/security/pam_nologin.so
	auth       sufficient	/lib/security/pam_winbind.so
	auth       required     /lib/security/pam_pwdb.so use_first_pass shadow nullok

Note in particular the use of the sufficient keyword and the use_first_pass keyword.

Now replace the account lines with this:


	account    required	/lib/security/pam_winbind.so

The next step is to join the domain. To do that use the samedit program like this:


	samedit -S '*' -W DOMAIN -UAdministrator

Then within samedit run the command:


	createuser MACHINE$ -j DOMAIN -L

This assumes your domain is called DOMAIN and your Samba workstation is called MACHINE.

Next copy libnss_winbind.so.2 to /lib and pam_winbind.so to /lib/security.

Finally, setup a smb.conf containing directives like the following:


  [global]
        winbind separator = +
        winbind cache time = 10
        template shell = /bin/bash
        template homedir = /home/%D/%U
        winbind uid = 10000-20000
        winbind gid = 10000-20000
        workgroup = DOMAIN
        security = domain
        password server = *

Now start winbindd and you should find that your user and group database is expanded to include your NT users and groups, and that you can login to your unix box as a domain user, using the DOMAIN+user syntax for the username. You may wish to use the commands "getent passwd" and "getent group" to confirm the correct operation of winbindd.

NOTES

The following notes are useful when configuring and running winbindd:

nmbd must be running on the local machine for winbindd to work.

winbindd queries the list of trusted domains for the Windows NT server on startup and when a SIGHUP is received. Thus, for a running winbindd to become aware of new trust relationships between servers, it must be sent a SIGHUP signal.

Client processes resolving names through the winbindd nsswitch module read an environment variable named WINBINDD_DOMAIN. If this variable contains a comma separated list of Windows NT domain names, then winbindd will only resolve users and groups within those Windows NT domains.

PAM is really easy to misconfigure. Make sure you know what you are doing when modifying PAM configuration files. It is possible to set up PAM such that you can no longer log into your system.

If more than one UNIX machine is running winbindd, then in general the user and groups ids allocated by winbindd will not be the same. The user and group ids will only be valid for the local machine.

If the the Windows NT RID to UNIX user and group id mapping file is damaged or destroyed then the mappings will be lost.

SIGNALS

The following signals can be used to manipulate the winbindd daemon.

SIGHUP

Reload the smb.conf file and apply any parameter changes to the running version of winbindd. This signal also clears any cached user and group information. The list of other domains trusted by winbindd is also reloaded.

SIGUSR1

The SIGUSR1 signal will cause winbindd to write status information to the winbind log file including information about the number of user and group ids allocated by winbindd.

Log files are stored in the filename specified by the log file parameter.

FILES

The following files are relevant to the operation of the winbindd daemon.

/etc/nsswitch.conf(5)

Name service switch configuration file.

/tmp/.winbindd/pipe

The UNIX pipe over which clients communicate with the winbindd program. For security reasons, the winbind client will only attempt to connect to the winbindd daemon if both the /tmp/.winbindd directory and /tmp/.winbindd/pipe file are owned by root.

/lib/libnss_winbind.so.X

Implementation of name service switch library.

$LOCKDIR/winbindd_idmap.tdb

Storage for the Windows NT rid to UNIX user/group id mapping. The lock directory is specified when Samba is initially compiled using the --with-lockdir option. This directory is by default /usr/local/samba/var/locks.

$LOCKDIR/winbindd_cache.tdb

Storage for cached user and group information.

AUTHOR

The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed by the Samba Team as an Open Source project.

winbindd was written by Tim Potter.