Microsoft Windows NT/200x/XP Professional platforms can participate in Domain Security. This section steps through the process for making a Windows 200x/XP Professional machine a member of a Domain Security environment. It should be noted that this process is identical when joining a domain that is controlled by Windows NT4/200x as well as a Samba PDC.

The screen capture shown in “The Computer Name Changes Panel Domain MIDEARTH” has a button labeled More.... This button opens a panel in which you can set (or change) the Primary DNS suffix of the computer. This is a parameter that mainly affects members of Microsoft Active Directory. Active Directory is heavily oriented around the DNS namespace.

Where NetBIOS technology uses WINS as well as UDP broadcast as key mechanisms for name resolution, Active Directory servers register their services with the Microsoft Dynamic DNS server. Windows clients must be able to query the correct DNS server to find the services (like which machines are domain controllers or which machines have the Netlogon service running).

The default setting of the Primary DNS suffix is the Active Directory domain name. When you change the Primary DNS suffix, this does not affect domain membership, but it can break network browsing and the ability to resolve your computer name to a valid IP address.

The Primary DNS suffix parameter principally affects MS Windows clients that are members of an Active Directory domain. Where the client is a member of a Samba domain, it is preferable to leave this field blank.

According to Microsoft documentation, “If this computer belongs to a group with Group Policy enabled on Primary DNS suffice of this computer, the string specified in the Group Policy is used as the primary DNS suffix and you might need to restart your computer to view the correct setting. The local setting is used only if Group Policy is disabled or unspecified.”

One of the frustrations expressed by subscribers to the Samba mailing lists revolves around the choice of where the default Samba Team build and installation process locates its Samba files. The location, chosen in the early 1990s, for the default installation is in the /usr/local/samba directory. This is a perfectly reasonable location, particularly given all the other Open Source software that installs into the /usr/local subdirectories.

Several UNIX vendors, and Linux vendors in particular, elected to locate the Samba files in a location other than the Samba Team default.

Linux vendors, working in conjunction with the Free Standards Group (FSG), Linux Standards Base (LSB), and File Hierarchy System (FHS), have elected to locate the configuration files under the /etc/samba directory, common binary files (those used by users) in the /usr/bin directory, and the administrative files (daemons) in the /usr/sbin directory. Support files for the Samba Web Admin Tool (SWAT) are located under the /usr/share directory, either in /usr/share/samba/swat or in /usr/share/swat. There are additional support files for smbd in the /usr/lib/samba directory tree. The files located there include the dynamically loadable modules for the passdb backend as well as for the VFS modules.

Samba creates runtime control files and generates log files. The runtime control files (tdb and dat files) are stored in the /var/lib/samba directory. Log files are created in /var/log/samba.

When Samba is built and installed using the default Samba Team process, all files are located under the /usr/local/samba directory tree. This makes it simple to find the files that Samba owns.

One way to find the Samba files that are installed on your UNIX/Linux system is to search for the location of all files called smbd. Here is an example:

root#  find / -name smbd -print

You can find the location of the configuration files by running:

root#  /path-to-binary-file/smbd -b | more
...
Paths:
   SBINDIR: /usr/sbin
   BINDIR: /usr/bin
   SWATDIR: /usr/share/samba/swat
   CONFIGFILE: /etc/samba/smb.conf
   LOGFILEBASE: /var/log/samba
   LMHOSTSFILE: /etc/samba/lmhosts
   LIBDIR: /usr/lib/samba
   SHLIBEXT: so
   LOCKDIR: /var/lib/samba
   PIDDIR: /var/run/samba
   SMB_PASSWD_FILE: /etc/samba/smbpasswd
   PRIVATE_DIR: /etc/samba
...

If you wish to locate the Samba version, just run:

root#  /path-to-binary-file/smbd -V
Version 3.0.20-SUSE

Many people have been caught by installation of Samba using the default Samba Team process when it was already installed by the platform vendor's method. If your platform uses RPM format packages, you can check to see if Samba is installed by executing:

root#  rpm -qa | grep samba
samba3-pdb-3.0.20-1
samba3-vscan-0.3.6-0
samba3-winbind-3.0.20-1
samba3-3.0.20-1
samba3-python-3.0.20-1
samba3-utils-3.0.20-1
samba3-doc-3.0.20-1
samba3-client-3.0.20-1
samba3-cifsmount-3.0.20-1
	

The package names, of course, vary according to how the vendor, or the binary package builder, prepared them.

Samba essentially consists of two or three daemons. A daemon is a UNIX application that runs in the background and provides services. An example of a service is the Apache Web server for which the daemon is called httpd. In the case of Samba, there are three daemons, two of which are needed as a minimum.

The Samba server is made up of the following daemons:

#!/bin/bash
#
# Script to start/stop samba
# Locate this in /sbin as a file called 'samba'

RCD=/etc/rc.d

if [ z$1 == 'z' ]; then
        echo $0 - No arguments given; must be start or stop.
        exit
fi

if [ $1 == 'start' ]; then
        ${RCD}/nmb start
        ${RCD}/smb start
        ${RCD}/winbind start

fi
if [ $1 == 'stop' ]; then
        ${RCD}/smb stop
        ${RCD}/winbind stop
        ${RCD}/nmb stop
fi
if [ $1 == 'restart' ]; then
        ${RCD}/smb stop
        ${RCD}/winbind stop
        ${RCD}/nmb stop
        sleep 5
        ${RCD}/nmb start
        ${RCD}/smb start
        ${RCD}/winbind start
fi
exit 0

When Samba has been packaged by an operating system vendor, the startup process is typically a custom feature of its integration into the platform as a whole. Please refer to your operating system platform administration manuals for specific information pertaining to correct management of Samba startup.

#!/bin/sh
#
# chkconfig: 345 81 35
# description: Starts and stops the Samba smbd and nmbd daemons \
#              used to provide SMB network services.

# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0
CONFIG=/etc/samba/smb.conf
# Check that smb.conf exists.
[ -f $CONFIG ] || exit 0

# See how we were called.
case "$1" in
  start)
        echo -n "Starting SMB services: "
        daemon smbd -D; daemon nmbd -D; echo;
        touch /var/lock/subsys/smb
        ;;
  stop)
        echo -n "Shutting down SMB services: "
        smbdpids=`ps guax | grep smbd | grep -v grep | awk '{print $2}'`
        for pid in $smbdpids; do
                kill -TERM $pid
        done
        killproc nmbd -TERM; rm -f /var/lock/subsys/smb
        echo ""
        ;;
  status)
        status smbd; status nmbd;
        ;;
  restart)
        echo -n "Restarting SMB services: "
        $0 stop; $0 start;
        echo "done."
        ;;
  *)
        echo "Usage: smb {start|stop|restart|status}"
        exit 1
esac

SUSE Linux implements individual control over each Samba daemon. A Samba control script that can be conveniently executed from the command line is shown in “A Useful Samba Control Script for SUSE Linux”. This can be located in the directory /sbin in a file called samba. This type of control script should be owned by user root and group root, and set so that only root can execute it.

A sample startup script for a Red Hat Linux system is shown in “A Sample Samba Control Script for Red Hat Linux”. This file could be located in the directory /etc/rc.d and can be called samba. A similar startup script is required to control winbind. If you want to find more information regarding startup scripts please refer to the packaging section of the Samba source code distribution tarball. The packaging files for each platform include a startup control file.

The following files are common to all DNS server configurations. Rather than repeat them multiple times, they are presented here for general reference.

$TTL 1W
@		IN SOA	@   root (
				42		; serial
				2D		; refresh
				4H		; retry
				6W		; expiry
				1W )		; minimum

		IN NS		@
		IN A		127.0.0.1

$TTL 1W
@		IN SOA		localhost.   root.localhost. (
				42		; serial
				2D		; refresh
				4H		; retry
				6W		; expiry
				1W )		; minimum

		IN NS		localhost.
1		IN PTR		localhost.

; This file is made available by InterNIC under anonymous FTP as
;       file                /domain/named.root
;       on server           FTP.INTERNIC.NET
; last update: Nov 5, 2002. Related version of root zone: 2002110501
; formerly NS.INTERNIC.NET
.                        3600000  IN  NS    A.ROOT-SERVERS.NET.
A.ROOT-SERVERS.NET.      3600000      A     198.41.0.4
; formerly NS1.ISI.EDU
.                        3600000      NS    B.ROOT-SERVERS.NET.
B.ROOT-SERVERS.NET.      3600000      A     128.9.0.107
; formerly C.PSI.NET
.                        3600000      NS    C.ROOT-SERVERS.NET.
C.ROOT-SERVERS.NET.      3600000      A     192.33.4.12
; formerly TERP.UMD.EDU
.                        3600000      NS    D.ROOT-SERVERS.NET.
D.ROOT-SERVERS.NET.      3600000      A     128.8.10.90
; formerly NS.NASA.GOV
.                        3600000      NS    E.ROOT-SERVERS.NET.
E.ROOT-SERVERS.NET.      3600000      A     192.203.230.10
; formerly NS.ISC.ORG
.                        3600000      NS    F.ROOT-SERVERS.NET.
F.ROOT-SERVERS.NET.      3600000      A     192.5.5.241
; formerly NS.NIC.DDN.MIL
.                        3600000      NS    G.ROOT-SERVERS.NET.
G.ROOT-SERVERS.NET.      3600000      A     192.112.36.4
; formerly AOS.ARL.ARMY.MIL
.                        3600000      NS    H.ROOT-SERVERS.NET.
H.ROOT-SERVERS.NET.      3600000      A     128.63.2.53
; formerly NIC.NORDU.NET
.                        3600000      NS    I.ROOT-SERVERS.NET.
I.ROOT-SERVERS.NET.      3600000      A     192.36.148.17
; operated by VeriSign, Inc. 
.                        3600000      NS    J.ROOT-SERVERS.NET.
J.ROOT-SERVERS.NET.      3600000      A     192.58.128.30
; housed in LINX, operated by RIPE NCC
.                        3600000      NS    K.ROOT-SERVERS.NET.
K.ROOT-SERVERS.NET.      3600000      A     193.0.14.129 
; operated by IANA
.                        3600000      NS    L.ROOT-SERVERS.NET.
L.ROOT-SERVERS.NET.      3600000      A     198.32.64.12
; housed in Japan, operated by WIDE
.                        3600000      NS    M.ROOT-SERVERS.NET.
M.ROOT-SERVERS.NET.      3600000      A     202.12.27.33
; End of File

The following procedure may be used as an alternative means of configuring the initial LDAP database. Many administrators prefer to have greater control over how system files get configured.

#!/bin/bash
#
# This script prepares the ldif LDAP load file only
#

# Pattern File Name
file=init-ldif.pat

# The name of my organization
ORGNAME="My Organization"

# My Internet domain. ie: if my domain is: buckets.org, INETDOMAIN="buckets"
INETDOMAIN="my-domain"

# In the above case, md domain is: buckets.org, TLDORG="org"
TLDORG="org"

# This is the Samba Domain/Workgroup Name
DOMNAME="MYWORKGROUP"

#
# Here We Go ...
#

cat <<EOF

How do you wish to refer to your organization?

Suggestions:
	Black Tire Company, Inc.
	Cat With Hat Ltd.

How would you like your organization name to appear?

EOF

echo "Your organization name is: $ORGNAME"
echo
echo "Enter a new name or, press Enter to Continue."
echo

echo -e -n "Name [$ORGNAME]: "
	read name

if [ ! -z "$name" ]; then 
	ORGNAME=${name}
fi
echo
sed "s/ORGNAME/${ORGNAME}/g" < $file > $file.tmp1

# Try to find smb.conf

if [ -e /usr/local/samba/lib/smb.conf ]; then
	CONF=/usr/local/samba/lib/smb.conf
elif [ -e /etc/samba/smb.conf ]; then
	CONF=/etc/samba/smb.conf
fi

echo "Samba Config File Location [$CONF]: "
echo
echo "Enter a new full path or press Enter to continue."
echo
echo -n "Samba Config File Location [$CONF]: "
	read name
if [ ! -z "$name" ]; then
	CONF=$name
fi
echo

# Find the name of our Domain/Workgroup
DOMNAME=`grep -i workgroup ${CONF} | sed "s/ //g" | cut -f2 -d=`
echo Domain Name: $DOMNAME
echo

sed "s/DOMNAME/${DOMNAME}/g" < $file.tmp1 > $file.tmp2

DOMSID=`net getlocalsid ${DOMNAME} | cut -f2 -d: | sed "s/ //g"`
echo Domain SID: $DOMSID

sed "s/DOMSID/${DOMSID}/g" < $file.tmp2 > $file.tmp1

cat <<EOL
The name of your Internet domain is now needed in a special format
as follows, if your domain name is mydomain.org, what we need is
the information in the form of:
	Domain ID: mydomain
	Top level: org

If your fully qualified hostname is: snoopy.bazaar.garagesale.net
where "snoopy" is the name of the machine,
Then the information needed is:
	Domain ID: garagesale
	Top Level: net

EOL
INETDOMAIN=`hostname -d | cut -f1 -d.`
echo Found the following domain name: `hostname -d`
echo "I think the bit we are looking for might be: $INETDOMAIN"
echo
echo -n "Enter the domain name or press Enter to continue: "
	read domnam
if [ ! -z $domnam ]; then
	INETDOMAIN=$domnam
fi
echo
sed "s/INETDOMAIN/${INETDOMAIN}/g" < $file.tmp1 > $file.tmp2
TLDORG=`hostname -d | sed "s/${INETDOMAIN}.//g"`
echo "The top level organization name I will use is: ${TLDORG}"
echo
echo -n "Enter the top level org name or press Enter to continue: "
	read domnam
if [ ! -z $domnam ]; then
        TLDORG=$domnam
fi
sed "s/TLDORG/${TLDORG}/g" < $file.tmp2 > $DOMNAME.ldif
rm $file.tmp*
exit 0

dn: dc=INETDOMAIN,dc=TLDORG
objectClass: dcObject
objectClass: organization
dc: INETDOMAIN
o: ORGNAME
description: Posix and Samba LDAP Identity Database

dn: cn=Manager,dc=INETDOMAIN,dc=TLDORG
objectClass: organizationalRole
cn: Manager
description: Directory Manager

dn: ou=People,dc=INETDOMAIN,dc=TLDORG
objectClass: top
objectClass: organizationalUnit
ou: People

dn: ou=Computers,dc=INETDOMAIN,dc=TLDORG
objectClass: top
objectClass: organizationalUnit
ou: Computers

dn: ou=Groups,dc=INETDOMAIN,dc=TLDORG
objectClass: top
objectClass: organizationalUnit
ou: Groups

dn: ou=Idmap,dc=INETDOMAIN,dc=TLDORG
objectClass: top
objectClass: organizationalUnit
ou: Idmap

dn: ou=Domains,dc=INETDOMAIN,dc=TLDORG
objectClass: top
objectClass: organizationalUnit
ou: Domains

dn: sambaDomainName=DOMNAME,ou=Domains,dc=INETDOMAIN,dc=TLDORG
objectClass: sambaDomain
sambaDomainName: DOMNAME
sambaSID: DOMSID
sambaAlgorithmicRidBase: 1000
structuralObjectClass: sambaDomain

dn: cn=domadmins,ou=Groups,dc=INETDOMAIN,dc=TLDORG
objectClass: posixGroup
objectClass: sambaGroupMapping
gidNumber: 512
cn: domadmins
sambaSID: DOMSID-512
sambaGroupType: 2
displayName: Domain Admins
description: Domain Administrators

dn: cn=domguests,ou=Groups,dc=INETDOMAIN,dc=TLDORG
objectClass: posixGroup
objectClass: sambaGroupMapping
gidNumber: 514
cn: domguests
sambaSID: DOMSID-514
sambaGroupType: 2
displayName: Domain Guests
description: Domain Guests Users

dn: cn=domusers,ou=Groups,dc=INETDOMAIN,dc=TLDORG
objectClass: posixGroup
objectClass: sambaGroupMapping
gidNumber: 513
cn: domusers
sambaSID: DOMSID-513
sambaGroupType: 2
displayName: Domain Users
description: Domain Users

The LDAP Account Manager (LAM) is an application suite that has been written in PHP. LAM can be used with any Web server that has PHP4 support. It connects to the LDAP server either using unencrypted connections or via SSL/TLS. LAM can be used to manage Posix accounts as well as SambaSAMAccounts for users, groups, and Windows machines (hosts).

LAM is available from the LAM home page and from its mirror sites. LAM has been released under the GNU GPL version 2. The current version of LAM is 0.4.9. Release of version 0.5 is expected in the third quarter of 2005.

Requirements:

LAM is a useful tool that provides a simple Web-based device that can be used to manage the contents of the LDAP directory to:

When correctly configured, LAM allows convenient management of UNIX (Posix) and Samba user, group, and windows domain member machine accounts.

The default password is “lam.” It is highly recommended that you use only an SSL connection to your Web server for all remote operations involving LAM. If you want secure connections, you must configure your Apache Web server to permit connections to LAM using only SSL.

An example of a working file is shown here in “LAM Profile Control File lam.conf”. This file has been stripped of comments to keep the size small. The comments and help information provided in the profile file that the wizard creates is very useful and will help many administrators to avoid pitfalls. Your configuration file obviously reflects the configuration options that are preferred at your site.

It is important that your LDAP server is running at the time that LAM is being configured. This permits you to validate correct operation. An example of the LAM login screen is provided in “The LDAP Account Manager Login Screen”.

Figure 15.6. The LDAP Account Manager Login Screen

The LAM configuration editor has a number of options that must be managed correctly. An example of use of the LAM configuration editor is shown in “The LDAP Account Manager Configuration Screen”. It is important that you correctly set the minimum and maximum UID/GID values that are permitted for use at your site. The default values may not be compatible with a need to modify initial default account values for well-known Windows network users and groups. The best work-around is to temporarily set the minimum values to zero (0) to permit the initial settings to be made. Do not forget to reset these to sensible values before using LAM to add additional users and groups.

Figure 15.7. The LDAP Account Manager Configuration Screen

LAM has some nice, but unusual features. For example, one unexpected feature in most application screens permits the generation of a PDF file that lists configuration information. This is a well thought out facility. This option has been edited out of the following screen shots to conserve space.

When you log onto LAM the opening screen drops you right into the user manager as shown in “The LDAP Account Manager User Edit Screen”. This is a logical action as it permits the most-needed facility to be used immediately. The editing of an existing user, as with the addition of a new user, is easy to follow and very clear in both layout and intent. It is a simple matter to edit generic settings, UNIX specific parameters, and then Samba account requirements. Each step involves clicking a button that intuitively drives you through the process. When you have finished editing simply press the Final button.

Figure 15.8. The LDAP Account Manager User Edit Screen

The edit screen for groups is shown in “The LDAP Account Manager Group Edit Screen”. As with the edit screen for user accounts, group accounts may be rapidly dealt with. “The LDAP Account Manager Group Membership Edit Screen” shows a sub-screen from the group editor that permits users to be assigned secondary group memberships.

Figure 15.9. The LDAP Account Manager Group Edit Screen

Figure 15.10. The LDAP Account Manager Group Membership Edit Screen

The final screen presented here is one that you should not normally need to use. Host accounts will be automatically managed using the smbldap-tools scripts. This means that the screen “The LDAP Account Manager Host Edit Screen” will, in most cases, not be used.

Figure 15.11. The LDAP Account Manager Host Edit Screen

One aspect of LAM that may annoy some users is the way it forces certain conventions on the administrator. For example, LAM does not permit the creation of Windows user and group accounts that contain spaces even though the underlying UNIX/Linux operating system may exhibit no problems with them. Given the propensity for using upper-case characters and spaces (particularly in the default Windows account names) this may cause some annoyance. For the rest, LAM is a very useful administrative tool.

The next major release, LAM 0.5, will have fewer restrictions and support the latest Samba features (e.g., logon hours). The new plugin-based architecture also allows management of much more different account types like plain UNIX accounts. The upload can now handle groups and hosts, too. Another important point is the tree view which allows browsing and editing LDAP objects directly.

# password to add/delete/rename configuration profiles
password: not24get

# default profile, without ".conf"
default: lam

ServerURL: ldap://massive.abmas.org:389
Admins: cn=Manager,dc=abmas,dc=biz
Passwd: not24get
usersuffix: ou=People,dc=abmas,dc=biz
groupsuffix: ou=Groups,dc=abmas,dc=biz
hostsuffix: ou=Computers,dc=abmas,dc=biz
domainsuffix: ou=Domains,dc=abmas,dc=biz
MinUID: 0
MaxUID: 65535
MinGID: 0
MaxGID: 65535
MinMachine: 20000
MaxMachine: 25000
userlistAttributes: #uid;#givenName;#sn;#uidNumber;#gidNumber
grouplistAttributes: #cn;#gidNumber;#memberUID;#description
hostlistAttributes: #cn;#description;#uidNumber;#gidNumber
maxlistentries: 30
defaultLanguage: en_GB:ISO-8859-1:English (Great Britain)
scriptPath: 
scriptServer: 
samba3: yes
cachetimeout: 5
pwdhash: SSHA

IMC (the IDEALX Mamagement Console) is a tool that can be used as the basis for a comprehensive web-based management interface for UNIX and Linux systems.

The Samba toolset is the first console developped for IMC. It offers a simple and ergonomic interface for managing a Samba domain controler. The goal is to give Linux administrators who need to manage production Samba servers an effective, intuitive and consistent management experience. An IMC screenshot of the user management tool is shown in “The IMC Samba User Account Screen”.

Figure 15.12. The IMC Samba User Account Screen

IMC is built on a set of Perl modules. Most modules are standard CPAN modules. Some are bundled with IMC, but will soon to be hosted on the CPAN independently, like Struts4P, a port of Struts to the Perl language.

For further information regarding IMC refer to the web site. Prebuilt RPM packages are also available.

The setting of the SUID/SGID bits on the file or directory permissions flag has particular consequences. If the file is executable and the SUID bit is set, it executes with the privilege of (with the UID of) the owner of the file. For example, if you are logged onto a system as a normal user (let's say as the user bobj), and you execute a file that is owned by the user root (uid = 0), and the file has the SUID bit set, then the file is executed as if you had logged in as the user root and then executed the file. The SUID bit effectively gives you (as bobj) administrative privilege for the use of that executable file.

The setting of the SGID bit does precisely the same as the effect of the SUID bit, except that it applies the privilege to the UNIX group setting. In other words, the file executes with the force of capability of the group.

When the SUID/SGID permissions are set on a directory, all files that are created within that directory are automatically given the ownership of the SUID user and the SGID group, as per the ownership of the directory in which the file is created. This means that the system level create() function executes with the SUID user and/or SGID group of the directory in which the file is created.

If you want to obtain the SUID behavior, simply execute the following command:

root#  chmod u+s file-or-directory

To set the SGID properties on a file or a directory, execute this command:

root#  chmod g+s file-or-directory

And to set both SUID and SGID properties, execute the following:

root#  chmod ug+s file-or-directory

Let's consider the example of a directory /data/accounts. The permissions on this directory before setting both SUID and SGID on this directory are:

root#  ls -al /data/accounts
total 1
drwxr-xr-x   10 root     root          232 Dec 18 17:08 .
drwxr-xr-x   21 root     root          600 Dec 17 23:15 ..
drwxrwxrwx    2 bobj     Domain Users  48 Dec 18 17:08 accounts/
drwx------    2 root     root           48 Jan 26  2002 lost+found

In this example, if the user maryv creates a file, it is owned by her. If maryv has the primary group of Accounts, the file is owned by the group Accounts, as shown in this listing:

root#  ls -al /data/accounts/maryvfile.txt
drw-rw-r--    2 maryv    Accounts     12346 Dec 18 17:53

Now you set the SUID and SGID and check the result as follows:

root#  chmod ug+s /data/accounts
root#  ls -al /data/accounts
total 1
drwxr-xr-x   10 root     root          232 Dec 18 17:08 .
drwxr-xr-x   21 root     root          600 Dec 17 23:15 ..
drwsrwsr-x    2 bobj     Domain Users  48 Dec 18 17:08 accounts
drwx------    2 root     root           48 Jan 26  2002 lost+found

If maryv creates a file in this directory after this change has been made, the file is owned by the user bobj, and the group is set to the group Domain Users, as shown here:

root#  chmod ug+s /data/accounts
root#  ls -al /data/accounts/maryvfile.txt
total 1
drw-rw-r--    2 bobj     Domain Users  12346 Dec 18 18:11 maryvfile.txt

The integrity of shared data is often viewed as a particularly emotional issue, especially where there are concurrent problems with multiuser data access. Contrary to the assertions of some who have experienced problems in either area, the cause has nothing to do with the phases of the moons of Jupiter.

The solution to concurrent multiuser data access problems must consider three separate areas from which the problem may stem:

Many database applications use some form of application-level access control. An example of one well-known application that uses application-level locking is Microsoft Access. Detailed guidance is provided here because this is the most common application for which problems have been reported.

Common applications that are affected by client- and server-side locking controls include MS Excel and Act!. Important locking guidance is provided here.

By file:        veto oplock files = myfile.mdb

By Pattern:     veto oplock files = /*.mdb/

On the Share:   oplocks = No
                level2 oplocks = No

On the server:
(in [global])   oplocks = No
                level2 oplocks = No

REGEDIT4

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
            Services\LanmanServer\Parameters]
      "EnableOplocks"=dword:00000000

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
            Services\LanmanWorkstation\Parameters]
      "UseOpportunisticLocking"=dword:00000000