Chapter 3. Secure Office Networking
Prev | Part I. Example Network Configurations | Next

## Chapter 3. Secure Office Networking

Congratulations, your Samba networking skills are developing nicely. You started out with three simple networks in “No-Frills Samba Servers”, and then in “Small Office Networking” you designed and built a network that provides a high degree of flexibility, integrity, and dependability. It was enough for the basic needs each was designed to fulfill. In this chapter you address a more complex set of needs. The solution you explore introduces you to basic features that are specific to Samba-3.

You should note that a working and secure solution could be implemented using Samba-2.2.x. In the exercises presented here, you are gradually using more Samba-3-specific features, so caution is advised for anyone who tries to use Samba-2.2.x with the guidance here given. To avoid confusion, this book is all about Samba-3. Let's get the exercises in this chapter underway.

## Introduction

You have made Mr. Meany a very happy man. Recently he paid you a fat bonus for work well done. It is one year since the last network upgrade. You have been quite busy. Two months ago Mr. Meany gave approval to hire Christine Roberson, who has taken over general network management. Soon she will provide primary user support. You have demonstrated that you can delegate responsibility and can plan and execute according to that plan. Above all, you have shown Mr. Meany that you are a responsible person. Today is a big day. Mr. Meany called you to his office at 9 a.m. for news you never expected: You are going to take charge of business operations. Mr. Meany is retiring and has entrusted the business to your capable hands.

Mr. Meany may be retiring from this company, but not from work. He is taking the opportunity to develop Abmas Accounting into a larger and more substantial company. He says that it took him many years to learn that there is no future in just running a business. He now realizes there is great personal satisfaction in the creation of career opportunities for people in the local community. He wants to do more for others, as he is doing for you. Today he spent a lot of time talking about his grand plan for growth, which you will deal with in the chapters ahead.

Over the past year, the growth projections were exceeded. The network has grown to meet the needs of 130 users. Along with growth, the demand for improved services and better functionality has also developed. You are about to make an interim improvement and then hand over all Help desk and network maintenance to Christine. Christine has professional certifications in Microsoft Windows as well as in Linux; she is a hard worker and quite likable. Christine does not want to manage the department (although she manages well). She gains job satisfaction when left to sort things out. Occasionally she wants to work with you on a challenging problem. When you told her about your move, she almost resigned, although she was reassured that a new manager would be hired to run Information Technology, and she would be responsible only for operations.

### Assignment Tasks

You promised the staff Internet services including Web browsing, electronic mail, virus protection, and a company Web site. Christine is eager to help turn the vision into reality. Let's see how close you can get to the promises made.

The network you are about to deliver will service 130 users today. Within a year, Abmas will aquire another company. Mr. Meany claims that within 2 years there will be well over 500 users on the network. You have bought into the big picture, so prepare for growth. You have purchased a new server and will implement a new network infrastructure.

You have decided to not recycle old network components. The only items that will be carried forward are notebook computers. You offered staff new notebooks, but not one person wanted the disruption for what was perceived as a marginal update. You decided to give everyone, even the notebook user, a new desktop computer.

You procured a DSL Internet connection that provides 1.5 Mb/sec (bidirectional) and a 10 Mb/sec ethernet port. You registered the domain `abmas.us`, and the Internet Service Provider (ISP) is supplying secondary DNS. Information furnished by your ISP is shown in “Abmas.US ISP Information”.

It is of paramount priority that under no circumstances will Samba offer service access from an Internet connection. You are paying an ISP to give, as part of its value-added services, full firewall protection for your connection to the outside world. The only services allowed in from the Internet side are the following destination ports: `http/https (ports 80 and 443), email (port 25), DNS (port 53)`. All Internet traffic will be allowed out after network address translation (NAT). No internal IP addresses are permitted through the NAT filter because complete privacy of internal network operations must be assured.

Table 3.1. Abmas.US ISP Information

Parameter | Value
--- | ---
Server IP Address | 123.45.67.66
DSL Device IP Address | 123.45.67.65
Network Address | 123.45.67.64/30
Gateway Address | 123.45.54.65
Primary DNS Server | 123.45.54.65
Secondary DNS Server | 123.45.54.32
Forwarding DNS Server | 123.45.12.23

Figure 3.1. Abmas Network Topology 130 Users

Christine recommended that desktop systems should be installed from a single cloned master system that has a minimum of locally installed software and loads all software off a central application server. The benefit of having the central application server is that it allows single-point maintenance of all business applications, a more efficient way to manage software. She further recommended installation of antivirus software on workstations as well as on the Samba server. Christine knows the dangers of potential virus infection and insists on a comprehensive approach to detective as well as corrective action to protect network operations.

A significant concern is the problem of managing company growth. Recently, a number of users had to share a PC while waiting for new machines to arrive. This presented some problems with desktop computers and software installation into the new users' desktop profiles.

## Dissection and Discussion

Many of the conclusions you draw here are obvious. Some requirements are not very clear or may simply be your means of drawing the most out of Samba-3. Much can be done more simply than you will demonstrate here, but keep in mind that the network must scale to at least 500 users. This means that some functionality will be overdesigned for the current 130-user environment.

### Technical Issues

In this exercise we use a 24-bit subnet mask for the two local networks. This, of course, limits our network to a maximum of 253 usable IP addresses. The network address range chosen is one assigned by RFC1918 for private networks. When the number of users on the network begins to approach the limit of usable addresses, it is a good idea to switch to a network address specified in RFC1918 in the 172.16.0.0/16 range. This is done in subsequent chapters.

The high growth rates projected are a good reason to use the `tdbsam` passdb backend. The use of `smbpasswd` for the backend may result in performance problems. The `tdbsam` passdb backend offers features that are not available with the older, flat ASCII-based `smbpasswd` database.

The proposed network design uses a single server to act as an Internet services host for electronic mail, Web serving, remote administrative access via SSH, Samba-based file and print services. This design is often chosen by sites that feel they cannot afford or justify the cost or overhead of having separate servers. It must be realized that if security of this type of server should ever be violated (compromised), the whole network and all data is at risk. Many sites continue to choose this type of solution; therefore, this chapter provides detailed coverage of key implementation aspects.

Samba will be configured to specifically not operate on the Ethernet interface that is directly connected to the Internet.

You know that your ISP is providing full firewall services, but you cannot rely on that. Always assume that human error will occur, so be prepared by using Linux firewall facilities based on `iptables` to effect NAT. Block all incoming traffic except to permitted well-known ports. You must also allow incoming packets to establish outgoing connections. You will permit all internal outgoing requests.

The configuration of Web serving, Web proxy services, electronic mail, and the details of generic antivirus handling are beyond the scope of this book and therefore are not covered except insofar as this affects Samba-3.

Notebook computers are configured to use a network login when in the office and a local account to log in while away from the office. Users store all work done in transit (away from the office) by using a local share for work files. Standard procedures dictate that on completion of the work that necessitates mobile file access, all work files are moved back to secure storage on the office server. Staff is instructed to not carry on any company notebook computer any files that are not absolutely required. This is a preventative measure to protect client information as well as private business records.

All applications are served from the central server from a share called `apps`. Microsoft Office XP Professional and OpenOffice 1.1.0 will be installed using a network (or administrative) installation. Accounting and financial management software can also be run only from the central application server. Notebook users are provided with locally installed applications on a need-to-have basis only.

The introduction of roaming profiles support means that users can move between desktop computer systems without constraint while retaining full access to their data. The desktop travels with them as they move.

The DNS server implementation must now address both internal and external needs. You forward DNS lookups to your ISP-provided server as well as the `abmas.us` external secondary DNS server.

Compared with the DHCP server configuration in “Small Office Networking”, “Abmas Accounting DHCP Server Configuration File /etc/dhcpd.conf”, the configuration used in this example has to deal with the presence of an Internet connection. The scope set for it ensures that no DHCP services will be offered on the external connection. All printers are configured as DHCP clients so that the DHCP server assigns the printer a fixed IP address by way of the Ethernet interface (MAC) address. One additional feature of this DHCP server configuration file is the inclusion of parameters to allow dynamic DNS (DDNS) operation.

This is the first implementation that depends on a correctly functioning DNS server. Comprehensive steps are included to provide for a fully functioning DNS server that also is enabled for DDNS operation. This means that DHCP clients can be autoregistered with the DNS server.

You are taking the opportunity to manually set the netbios name of the Samba server to a name other than what will be automatically resolved. You are doing this to ensure that the machine has the same NetBIOS name on both network segments.

As in the previous network configuration, printing in this network configuration uses direct raw printing (i.e., no smart printing and no print driver autodownload to Windows clients). Printer drivers are installed on the Windows client manually. This is not a problem because Christine is to install and configure one single workstation and then clone that configuration, using Norton Ghost, to all workstations. Each machine is identical, so this should pose no problem.

#### Hardware Requirements

This server runs a considerable number of services. From similarly configured Linux installations, the approximate calculated memory requirements are as shown in “Estimation of Memory Requirements”.

Example 3.1. Estimation of Memory Requirements

    Application  Memory per User    130 Users      500 Users
       Name        (MBytes)       Total MBytes   Total MBytes
    -----------  ---------------  ------------   ------------
    DHCP              2.5               3              3
    DNS              16.0              16             16
    Samba (nmbd)     16.0              16             16
    Samba (winbind)  16.0              16             16
    Samba (smbd)      4.0             520           2000
    Apache           10.0 (20 User)   200            200
    CUPS              3.5              16             32
    Basic OS        256.0             256            256
                                  -------------- --------------
        Total:                       1043 MBytes    2539 MBytes
                                  -------------- --------------

You should add a safety margin of at least 50% to these estimates. The minimum system memory recommended for initial startup 1 GB, but to permit the system to scale to 500 users, it makes sense to provision the machine with 4 GB memory. An initial configuration with only 1 GB memory would lead to early performance complaints as the system load builds up. Given the low cost of memory, it does not make sense to compromise in this area.

Aggregate input/output loads should be considered for sizing network configuration as well as disk subsystems. For network bandwidth calculations, one would typically use an estimate of 0.1 MB/sec per user. This suggests that 100-Base-T (approx. 10 MB/sec) would deliver below acceptable capacity for the initial user load. It is therefore a good idea to begin with 1 Gb Ethernet cards for the two internal networks, each attached to a 1 Gb Ethernet switch that provides connectivity to an expandable array of 100-Base-T switched ports.

Considering the choice of 1 Gb Ethernet interfaces for the two local network segments, the aggregate network I/O capacity will be 2100 Mb/sec (about 230 MB/sec), an I/O demand that would require a fast disk storage I/O capability. Peak disk throughput is limited by the disk subsystem chosen. It is desirable to provide the maximum I/O bandwidth affordable. If a low-cost solution must be chosen, 3Ware IDE RAID Controllers are a good choice. These controllers can be fitted into a 64-bit, 66 MHz PCI-X slot. They appear to the operating system as a high-speed SCSI controller that can operate at the peak of the PCI-X bandwidth (approximately 450 MB/sec). Alternative SCSI-based hardware RAID controllers should also be considered. Alternately, it makes sense to purchase well-known, branded hardware that has appropriate performance specifications. As a minimum, one should attempt to provide a disk subsystem that can deliver I/O rates of at least 100 MB/sec.

Disk storage requirements may be calculated as shown in “Estimation of Disk Storage Requirements”.

Example 3.2. Estimation of Disk Storage Requirements

    Corporate Data: 100 MBytes/user per year
    Email Storage:  500 MBytes/user per year
    Applications:   5000 MBytes
    Safety Buffer:  At least 50%

    Given 500 Users and 2 years:
    -----------------------------
            Corporate Data:  2 x 100 x 500 = 100000 MBytes = 100 GBytes
            Email Storage:   2 x 500 x 500 = 500000 MBytes = 500 GBytes
            Applications:                      5000 MBytes =   5 GBytes
                                           ----------------------------
                                 Total:                      605 GBytes
                 Add 50% buffer                              303 GBytes
                           Recommended Storage:              908 GBytes

The preferred storage capacity should be approximately 1 Terabyte. Use of RAID level 5 with two hot spare drives would require an 8-drive by 200 GB capacity per drive array.

### Political Issues

Your industry is coming under increasing accountability pressures. Increased paranoia is necessary so you can demonstrate that you have acted with due diligence. You must not trust your Internet connection.

Apart from permitting more efficient management of business applications through use of an application server, your primary reason for the decision to implement this is that it gives you greater control over software licensing.

You are well aware that the current configuration results in some performance issues as the size of the desktop profile grows. Given that users use Microsoft Outlook Express, you know that the storage implications of the `.PST` file is something that needs to be addressed later.

## Implementation

“Abmas Network Topology 130 Users” demonstrates the overall design of the network that you will implement.

The information presented here assumes that you are already familiar with many basic steps. As this stands, the details provided already extend well beyond just the necessities of Samba configuration. This decision is deliberate to ensure that key determinants of a successful installation are not overlooked. This is the last case that documents the finite minutiae of DHCP and DNS server configuration. Beyond the information provided here, there are many other good reference books on these subjects.

The `smb.conf` file has the following noteworthy features:

- The NetBIOS name of the Samba server is set to `DIAMOND`.

- The Domain name is set to `PROMISES`.

- Ethernet interface `eth0` is attached to the Internet connection and is externally exposed. This interface is explicitly not available for Samba to use. Samba listens on this interface for broadcast messages but does not broadcast any information on `eth0`, nor does it accept any connections from it. This is achieved by way of the `interfaces` parameter and the `bind interfaces only` entry.

- The `passdb backend` parameter specifies the creation and use of the `tdbsam` password backend. This is a binary database that has excellent scalability for a large number of user account entries.

- WINS serving is enabled by the wins support = Yes, and name resolution is set to use it by means of the name resolve order = wins bcast hosts entry.

- The Samba server is configured for use by Windows clients as a time server.

- Samba is configured to directly interface with CUPS via the direct internal interface that is provided by CUPS libraries. This is achieved with the printing = CUPS as well as the printcap name = CUPS entries.

- External interface scripts are provided to enable Samba to interface smoothly to essential operating system functions for user and group management. This is important to enable workstations to join the Domain and is also important so that you can use the Windows NT4 Domain User Manager as well as the Domain Server Manager. These tools are provided as part of the `SRVTOOLS.EXE` toolkit that can be downloaded from the Microsoft FTP site.

- The `smb.conf` file specifies that the Samba server will operate in (default) `security = user` mode[5] (User Mode).

- Domain logon services as well as a Domain logon script are specified. The logon script will be used to add robustness to the overall network configuration.

- Roaming profiles are enabled through the specification of the parameter, logon path = \\%L\profiles\%U. The value of this parameter translates the `%L` to the name by which the Samba server is called by the client (for this configuration, it translates to the name `DIAMOND`), and the `%U` will translate to the name of the user within the context of the connection made to the profile share. It is the administrator's responsibility to ensure there is a directory in the root of the profile share for each user. This directory must be owned by the user also. An exception to this requirement is when a profile is created for group use.

- Precautionary veto is effected for particular Windows file names that have been targeted by virus-related activity. Additionally, Microsoft Office files are vetoed from opportunistic locking controls. This should help to prevent lock contention-related file access problems.

- Every user has a private home directory on the UNIX/Linux host. This is mapped to a network drive that is the same for all users.

The configuration of the server is the most complex so far. The following steps are used:

1. Basic System Configuration

2. Samba Configuration

3. DHCP and DNS Server Configuration

4. Printer Configuration

5. Process Start-up Configuration

6. Validation

7. Application Share Configuration

8. Windows Client Configuration

The following sections cover each step in logical and defined detail.

### Basic System Configuration

The preparation in this section assumes that your SUSE Enterprise Linux Server 8.0 system has been freshly installed. It prepares basic files so that the system is ready for comprehensive operation in line with the network diagram shown in “Abmas Network Topology 130 Users”.

Procedure 3.1. Server Configuration Steps

1. Using the UNIX/Linux system tools, name the server `server.abmas.us`. Verify that your hostname is correctly set by running:

       root#  uname -n
       server

   An alternate method to verify the hostname is:

       root#  hostname -f
       server.abmas.us

2. Edit your `/etc/hosts` file to include the primary names and addresses of all network interfaces that are on the host server. This is necessary so that during startup the system can resolve all its own names to the IP address prior to startup of the DNS server. An example of entries that should be in the `/etc/hosts` file is:

       127.0.0.1       localhost
       192.168.1.1     sleeth1.abmas.biz sleeth1 diamond
       192.168.2.1     sleeth2.abmas.biz sleeth2
       123.45.67.66    server.abmas.us server

   You should check the startup order of your system. If the CUPS print server is started before the DNS server (`named`), you should also include an entry for the printers in the `/etc/hosts` file, as follows:

       192.168.1.20    qmsa.abmas.biz qmsa
       192.168.1.30    hplj6a.abmas.biz hplj6a
       192.168.2.20    qmsf.abmas.biz qmsf
       192.168.2.30    hplj6f.abmas.biz hplj6f

   The printer entries are not necessary if `named` is started prior to startup of `cupsd`, the CUPS daemon.

3. The host server is acting as a router between the two internal network segments as well as for all Internet access. This necessitates that IP forwarding be enabled. This can be achieved by adding to the `/etc/rc.d/boot.local` an entry as follows:

       echo 1 > /proc/sys/net/ipv4/ip_forward

   To ensure that your kernel is capable of IP forwarding during configuration, you may wish to execute that command manually also. This setting permits the Linux system to act as a router.[6]

4. Installation of a basic firewall and NAT facility is necessary. The following script can be installed in the `/usr/local/sbin` directory. It is executed from the `/etc/rc.d/boot.local` startup script. In your case, this script is called `abmas-netfw.sh`. The script contents are shown in “NAT Firewall Configuration Script”.

   Example 3.3. NAT Firewall Configuration Script

       #!/bin/sh
       echo -e "\n\nLoading NAT firewall.\n"
       IPTABLES=/usr/sbin/iptables
       EXTIF="eth0"
       INTIFA="eth1"
       INTIFB="eth2"

       /sbin/depmod -a
       /sbin/modprobe ip_tables
       /sbin/modprobe ip_conntrack
       /sbin/modprobe ip_conntrack_ftp
       /sbin/modprobe iptable_nat
       /sbin/modprobe ip_nat_ftp
       $IPTABLES -P INPUT DROP
       $IPTABLES -F INPUT
       $IPTABLES -P OUTPUT ACCEPT
       $IPTABLES -F OUTPUT
       $IPTABLES -P FORWARD DROP
       $IPTABLES -F FORWARD

       $IPTABLES -A INPUT -i lo -j ACCEPT
       $IPTABLES -A INPUT -i $INTIFA -j ACCEPT
       $IPTABLES -A INPUT -i $INTIFB -j ACCEPT
       $IPTABLES -A INPUT -i $EXTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
       # Enable incoming traffic for: SSH, SMTP, DNS(tcp), HTTP, HTTPS
       for i in 22 25 53 80 443
       do
               $IPTABLES -A INPUT -i $EXTIF -p tcp --dport $i  -j ACCEPT
       done
       # Allow DNS(udp)
       $IPTABLES -A INPUT -i $EXTIF -p udp -dport 53  -j ACCEPT
       echo "Allow all connections OUT and only existing and specified ones IN"
       $IPTABLES -A FORWARD -i $EXTIF -o $INTIFA -m state \
                                         --state ESTABLISHED,RELATED -j ACCEPT
       $IPTABLES -A FORWARD -i $EXTIF -o $INTIFB -m state \
                                         --state ESTABLISHED,RELATED -j ACCEPT
       $IPTABLES -A FORWARD -i $INTIFA -o $EXTIF -j ACCEPT
       $IPTABLES -A FORWARD -i $INTIFB -o $EXTIF -j ACCEPT
       $IPTABLES -A FORWARD -j LOG
       echo "   Enabling SNAT (MASQUERADE) functionality on $EXTIF"
       $IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
       echo "1" > /proc/sys/net/ipv4/ip_forward
       echo -e "\nNAT firewall done.\n"

5. Execute the following to make the script executable:

       root#  chmod 755 /usr/local/sbin/abmas-natfw.sh

   You must now edit `/etc/rc.d/boot.local` to add an entry that runs your `abmas-natfw.sh` script. The following entry works for you:

       #! /bin/sh
       #
       # Copyright (c) 2002 SUSE Linux AG Nuernberg, Germany.
       # All rights reserved.
       #
       # Author: Werner Fink, 1996
       #         Burchard Steinbild, 1996
       #
       # /etc/init.d/boot.local
       #
       # script with local commands to be executed from init on system startup
       #
       # Here you should add things that should happen directly after booting
       # before we're going to the first run level.
       #
       /usr/local/sbin/abmas-natfw.sh

The server is now ready for Samba configuration. During the validation step, you remove the entry for the Samba server `diamond` from the `/etc/hosts` file. This is done after you are satisfied that DNS-based name resolution is functioning correctly.

### Samba Configuration

When you have completed this section, the Samba server is ready for testing and validation; however, testing and validation have to wait until DHCP, DNS, and printing (CUPS) services have been configured.

Procedure 3.2. Samba Configuration Steps

1. Install the Samba-3 binary RPM from the Samba-Team FTP site. Assuming that the binary RPM file is called `samba-3.0.20-1.i386.rpm`, one way to install this file is as follows:

       root#  rpm -Uvh samba-3.0.20-1.i386.rpm

   This operation must be performed while logged in as the `root` user. Successful operation is clearly indicated. If this installation should fail for any reason, refer to the operating system manufacturer's documentation for guidance.

2. Install the `smb.conf` file shown in “130 User Network with tdbsam [globals] Section”, “130 User Network with tdbsam Services Section Part A”, and “130 User Network with tdbsam Services Section Part B”. Concatenate (join) all three files to make a single `smb.conf` file. The final, fully qualified path for this file should be `/etc/samba/smb.conf`.

   Example 3.4. 130 User Network with tdbsam [globals] Section

   # Global parameters
   `[global]`
   `workgroup = PROMISES`
   `netbios name = DIAMOND`
   `interfaces = eth1, eth2, lo`
   `bind interfaces only = Yes`
   `passdb backend = tdbsam`
   `pam password change = Yes`
   `passwd program = /usr/bin/passwd %u`
   `passwd chat = *New*Password* %n\n *Re-enter*new*password*%n\n *Password*changed*`
   `username map = /etc/samba/smbusers`
   `unix password sync = Yes`
   `log level = 1`
   `syslog = 0`
   `log file = /var/log/samba/%m`
   `max log size = 50`
   `smb ports = 139`
   `name resolve order = wins bcast hosts`
   `time server = Yes`
   `printcap name = CUPS`
   `show add printer wizard = No`
   `add user script = /usr/sbin/useradd -m '%u'`
   `delete user script = /usr/sbin/userdel -r '%u'`
   `add group script = /usr/sbin/groupadd '%g'`
   `delete group script = /usr/sbin/groupdel '%g'`
   `add user to group script = /usr/sbin/usermod -G '%g' '%u'`
   `add machine script = /usr/sbin/useradd -s /bin/false -d /tmp '%u'`
   `shutdown script = /var/lib/samba/scripts/shutdown.sh`
   `abort shutdown script = /sbin/shutdown -c`
   `logon script = scripts\logon.bat`
   `logon path = \\%L\profiles\%U`
   `logon drive = X:`
   `logon home = \\%L\%U`
   `domain logons = Yes`
   `preferred master = Yes`
   `wins support = Yes`
   `utmp = Yes`
   `map acl inherit = Yes`
   `printing = cups`
   `cups options = Raw`
   `veto files = /*.eml/*.nws/*.{*}/`
   `veto oplock files = /*.doc/*.xls/*.mdb/`

   Example 3.5. 130 User Network with tdbsam Services Section Part A

   `[homes]`
   `comment = Home Directories`
   `valid users = %S`
   `read only = No`
   `browseable = No`
   `[printers]`
   `comment = SMB Print Spool`
   `path = /var/spool/samba`
   `guest ok = Yes`
   `printable = Yes`
   `use client driver = Yes`
   `default devmode = Yes`
   `browseable = No`
   `[netlogon]`
   `comment = Network Logon Service`
   `path = /var/lib/samba/netlogon`
   `guest ok = Yes`
   `locking = No`
   `[profiles]`
   `comment = Profile Share`
   `path = /var/lib/samba/profiles`
   `read only = No`
   `profile acls = Yes`
   `[accounts]`
   `comment = Accounting Files`
   `path = /data/accounts`
   `read only = No`

   Example 3.6. 130 User Network with tdbsam Services Section Part B

   `[service]`
   `comment = Financial Services Files`
   `path = /data/service`
   `read only = No`
   `[pidata]`
   `comment = Property Insurance Files`
   `path = /data/pidata`
   `read only = No`
   `[apps]`
   `comment = Application Files`
   `path = /apps`
   `read only = Yes`
   `admin users = bjordan`

3. Add the `root` user to the password backend as follows:

       root#  smbpasswd -a root
       New SMB password: XXXXXXXX
       Retype new SMB password: XXXXXXXX
       root#

   The `root` account is the UNIX equivalent of the Windows Domain Administrator. This account is essential in the regular maintenance of your Samba server. It must never be deleted. If for any reason the account is deleted, you may not be able to recreate this account without considerable trouble.

4. Create the username map file to permit the `root` account to be called `Administrator` from the Windows network environment. To do this, create the file `/etc/samba/smbusers` with the following contents:

       ####
       # User mapping file
       ####
       # File Format
       # -----------
       # Unix_ID = Windows_ID
       #
       # Examples:
       # root = Administrator
       # janes = "Jane Smith"
       # jimbo = Jim Bones
       #
       # Note: If the name contains a space it must be double quoted.
       #       In the example above the name 'jimbo' will be mapped to Windows
       #       user names 'Jim' and 'Bones' because the space was not quoted.
       #######################################################################
       root = Administrator
       ####
       # End of File
       ####

5. Create and map Windows Domain Groups to UNIX groups. A sample script is provided in “Small Office Networking”, “Script to Map Windows NT Groups to UNIX Groups”. Create a file containing this script. We called ours `/etc/samba/initGrps.sh`. Set this file so it can be executed, and then execute the script. Sample output should be as follows:

   Example 3.7. Script to Map Windows NT Groups to UNIX Groups

       #!/bin/bash
       #
       # initGrps.sh
       #

       # Create UNIX groups
       groupadd acctsdep
       groupadd finsrvcs

       # Map Windows Domain Groups to UNIX groups
       net groupmap add ntgroup="Domain Admins"  unixgroup=root type=d
       net groupmap add ntgroup="Domain Users"   unixgroup=users type=d
       net groupmap add ntgroup="Domain Guests"  unixgroup=nobody type=d

       # Add Functional Domain Groups
       net groupmap add ntgroup="Accounts Dept"  unixgroup=acctsdep type=d
       net groupmap add ntgroup="Financial Services" unixgroup=finsrvcs type=d
       net groupmap add ntgroup="Insurance Group"     unixgroup=piops type=d

       # Map Windows NT machine local groups to local UNIX groups
       # Mapping of local groups is not necessary and not functional
       # for this installation.

       root#  chmod 755 initGrps.sh
       root#  /etc/samba # ./initGrps.sh
       Updated mapping entry for Domain Admins
       Updated mapping entry for Domain Users
       Updated mapping entry for Domain Guests
       No rid or sid specified, choosing algorithmic mapping
       Successfully added group Accounts Dept to the mapping db
       No rid or sid specified, choosing algorithmic mapping
       Successfully added group Domain Guests to the mapping db

       root#  /etc/samba # net groupmap list | sort
       Account Operators (S-1-5-32-548) -> -1
       Accounts Dept (S-1-5-21-179504-2437109-488451-2003) -> acctsdep
       Administrators (S-1-5-32-544) -> -1
       Backup Operators (S-1-5-32-551) -> -1
       Domain Admins (S-1-5-21-179504-2437109-488451-512) -> root
       Domain Guests (S-1-5-21-179504-2437109-488451-514) -> nobody
       Domain Users (S-1-5-21-179504-2437109-488451-513) -> users
       Financial Services (S-1-5-21-179504-2437109-488451-2005) -> finsrvcs
       Guests (S-1-5-32-546) -> -1
       Power Users (S-1-5-32-547) -> -1
       Print Operators (S-1-5-32-550) -> -1
       Replicators (S-1-5-32-552) -> -1
       System Operators (S-1-5-32-549) -> -1
       Users (S-1-5-32-545) -> -1

6. There is one preparatory step without which you will not have a working Samba network environment. You must add an account for each network user. For each user who needs to be given a Windows Domain account, make an entry in the `/etc/passwd` file as well as in the Samba password backend. Use the system tool of your choice to create the UNIX system account, and use the Samba `smbpasswd` to create a Domain user account. There are a number of tools for user management under UNIX, such as `useradd`, and `adduser`, as well as a plethora of custom tools. You also want to create a home directory for each user. You can do this by executing the following steps for each user:

       root#  useradd -m username
       root#  passwd username
       Changing password for username.
       New password: XXXXXXXX
       Re-enter new password: XXXXXXXX
       Password changed
       root#  smbpasswd -a username
       New SMB password: XXXXXXXX
       Retype new SMB password: XXXXXXXX
       Added user username.

   You do of course use a valid user login ID in place of `username`.

7. Using the preferred tool for your UNIX system, add each user to the UNIX groups created previously as necessary. File system access control will be based on UNIX group membership.

8. Create the directory mount point for the disk subsystem that can be mounted to provide data storage for company files. In this case the mount point is indicated in the `smb.conf` file is `/data`. Format the file system as required, and mount the formatted file system partition using appropriate system tools.

9. Create the top-level file storage directories for data and applications as follows:

       root#  mkdir -p /data/{accounts,finsrvcs}
       root#  mkdir -p /apps
       root#  chown -R root:root /data
       root#  chown -R root:root /apps
       root#  chown -R bjordan:acctsdep /data/accounts
       root#  chown -R bjordan:finsrvcs /data/finsrvcs
       root#  chmod -R ug+rwxs,o-rwx /data
       root#  chmod -R ug+rwx,o+rx-w /apps

   Each department is responsible for creating its own directory structure within the departmental share. The directory root of the `accounts` share is `/data/accounts`. The directory root of the `finsvcs` share is `/data/finsvcs`. The `/apps` directory is the root of the `apps` share that provides the application server infrastructure.

10. The `smb.conf` file specifies an infrastructure to support roaming profiles and network logon services. You can now create the file system infrastructure to provide the locations on disk that these services require. Adequate planning is essential, since desktop profiles can grow to be quite large. For planning purposes, a minimum of 200 MB of storage should be allowed per user for profile storage. The following commands create the directory infrastructure needed:

        root#  mkdir -p /var/spool/samba
        root#  mkdir -p /var/lib/samba/{netlogon/scripts,profiles}
        root#  chown -R root:root /var/spool/samba
        root#  chown -R root:root /var/lib/samba
        root#  chmod a+rwxt /var/spool/samba
        root#  chmod 2775 /var/lib/samba/profiles
        root#  chgrp users /var/lib/samba/profiles

    For each user account that is created on the system, the following commands should be executed:

        root#  mkdir /var/lib/samba/profiles/'username'
        root#  chown 'username':users /var/lib/samba/profiles/'username'
        root#  chmod ug+wrx,o+rx,-w /var/lib/samba/profiles/'username'

11. Create a logon script. It is important that each line is correctly terminated with a carriage return and line-feed combination (i.e., DOS encoding). The following procedure works if the right tools (`unix2dos` and `dos2unix`) are installed. First, create a file called `/var/lib/samba/netlogon/scripts/logon.bat.unix` with the following contents:

        net time \\diamond /set /yes
        net use h: /home
        net use p: \\diamond\apps

    Convert the UNIX file to a DOS file using the `unix2dos` as shown here:

        root#  unix2dos < /var/lib/samba/netlogon/scripts/logon.bat.unix \
        	> /var/lib/samba/netlogon/scripts/logon.bat

### Configuration of DHCP and DNS Servers

DHCP services are a basic component of the entire network client installation. DNS operation is foundational to Internet access as well as to trouble-free operation of local networking. When you have completed this section, the server should be ready for solid duty operation.

Procedure 3.3. DHCP and DNS Server Configuration Steps

1. Create a file called `/etc/dhcpd.conf` with the contents as shown in “DHCP Server Configuration File /etc/dhcpd.conf”.

   Example 3.8. DHCP Server Configuration File `/etc/dhcpd.conf`

       # Abmas Accounting Inc.
       default-lease-time 86400;
       max-lease-time 172800;
       default-lease-time 86400;
       option ntp-servers 192.168.1.1;
       option domain-name "abmas.biz";
       option domain-name-servers 192.168.1.1, 192.168.2.1;
       option netbios-name-servers 192.168.1.1, 192.168.2.1;
       option netbios-node-type 8;       ### Node type = Hybrid ###
       ddns-updates on;                  ### Dynamic DNS enabled ###
       ddns-update-style interim;

       subnet 192.168.1.0 netmask 255.255.255.0 {
               range dynamic-bootp 192.168.1.128 192.168.1.254;
               option subnet-mask 255.255.255.0;
               option routers 192.168.1.1;
               allow unknown-clients;
               host qmsa {
                       hardware ethernet 08:00:46:7a:35:e4;
                       fixed-address 192.168.1.20;
                       }
               host hplj6a {
                       hardware ethernet 00:03:47:cb:81:e0;
                       fixed-address 192.168.1.30;
                       }
               }
       subnet 192.168.2.0 netmask 255.255.255.0 {
               range dynamic-bootp 192.168.2.128 192.168.2.254;
               option subnet-mask 255.255.255.0;
               option routers 192.168.2.1;
               allow unknown-clients;
               host qmsf {
                       hardware ethernet 01:04:31:db:e1:c0;
                       fixed-address 192.168.1.20;
               	}
               host hplj6f {
                       hardware ethernet 00:03:47:cf:83:e2;
                       fixed-address 192.168.2.30;
                       }
       	}
       subnet 127.0.0.0 netmask 255.0.0.0 {
               }
       subnet 123.45.67.64 netmask 255.255.255.252 {
               }

2. Create a file called `/etc/named.conf` that has the combined contents of the “DNS Master Configuration File /etc/named.conf Master Section”, “DNS Master Configuration File /etc/named.conf Forward Lookup Definition Section”, and “DNS Master Configuration File /etc/named.conf Reverse Lookup Definition Section” files that are concatenated (merged) in this specific order.

3. Create the files shown in their respective directories as shown in DNS (named) Resource Files.

   Table 3.2. DNS (named) Resource Files

   Reference | File Location
   --- | ---
   “DNS Localhost Forward Zone File: /var/lib/named/localhost.zone” | /var/lib/named/localhost.zone
   “DNS Localhost Reverse Zone File: /var/lib/named/127.0.0.zone” | /var/lib/named/127.0.0.zone
   “DNS Root Name Server Hint File: /var/lib/named/root.hint” | /var/lib/named/root.hint
   “DNS Abmas.biz Forward Zone File” | /var/lib/named/master/abmas.biz.hosts
   “DNS Abmas.us Forward Zone File” | /var/lib/named/abmas.us.hosts
   “DNS 192.168.1 Reverse Zone File” | /var/lib/named/192.168.1.0.rev
   “DNS 192.168.2 Reverse Zone File” | /var/lib/named/192.168.2.0.rev

   Example 3.9. DNS Master Configuration File `/etc/named.conf` Master Section

       ###
       # Abmas Biz DNS Control File
       ###
       # Date: November 15, 2003
       ###
       options {
       	directory "/var/lib/named";
       	forwarders {
       		123.45.12.23;
       		};
       	forward first;
       	listen-on {
       		mynet;
       		};
       	auth-nxdomain yes;
       	multiple-cnames yes;
       	notify no;
       };

       zone "." in {
       	type hint;
       	file "root.hint";
       };

       zone "localhost" in {
       	type master;
       	file "localhost.zone";
       };

       zone "0.0.127.in-addr.arpa" in {
       	type master;
       	file "127.0.0.zone";
       };

       acl mynet {
       	192.168.1.0/24;
       	192.168.2.0/24;
       	127.0.0.1;
       };

       acl seconddns {
       	123.45.54.32;
       };

   Example 3.10. DNS Master Configuration File `/etc/named.conf` Forward Lookup Definition Section

       zone "abmas.biz" {
       	type master;
       	file "/var/lib/named/master/abmas.biz.hosts";
       	allow-query {
       		mynet;
       	};
       	allow-transfer {
       		mynet;
       	};
       	allow-update {
       		mynet;
       	};
       };

       zone "abmas.us" {
       	type master;
       	file "/var/lib/named/master/abmas.us.hosts";
       	allow-query {
       		any;
       	};
       	allow-transfer {
       		seconddns;
       	};
       };

   Example 3.11. DNS Master Configuration File `/etc/named.conf` Reverse Lookup Definition Section

       zone "1.168.192.in-addr.arpa" {
       	type master;
       	file "/var/lib/named/master/192.168.1.0.rev";
       	allow-query {
       		mynet;
       	};
       	allow-transfer {
       		mynet;
       	};
       	allow-update {
       		mynet;
       	};
       };

       zone "2.168.192.in-addr.arpa" {
       	type master;
       	file "/var/lib/named/master/192.168.2.0.rev";
       	allow-query {
       		mynet;
       	};
       	allow-transfer {
       		mynet;
       	};
       	allow-update {
       		mynet;
       	};
       };

   Example 3.12. DNS 192.168.1 Reverse Zone File

       $ORIGIN .
       $TTL 38400	; 10 hours 40 minutes
       1.168.192.in-addr.arpa	IN SOA	sleeth.abmas.biz. root.abmas.biz. (
       				2003021825 ; serial
       				10800      ; refresh (3 hours)
       				3600       ; retry (1 hour)
       				604800     ; expire (1 week)
       				38400      ; minimum (10 hours 40 minutes)
       				)
       			NS	sleeth1.abmas.biz.
       $ORIGIN 1.168.192.in-addr.arpa.
       1			PTR	sleeth1.abmas.biz.
       20			PTR	qmsa.abmas.biz.
       30			PTR	hplj6a.abmas.biz.

   Example 3.13. DNS 192.168.2 Reverse Zone File

       $ORIGIN .
       $TTL 38400	; 10 hours 40 minutes
       2.168.192.in-addr.arpa	IN SOA	sleeth.abmas.biz. root.abmas.biz. (
       				2003021825 ; serial
       				10800      ; refresh (3 hours)
       				3600       ; retry (1 hour)
       				604800     ; expire (1 week)
       				38400      ; minimum (10 hours 40 minutes)
       				)
       			NS	sleeth2.abmas.biz.
       $ORIGIN 2.168.192.in-addr.arpa.
       1			PTR	sleeth2.abmas.biz.
       20			PTR	qmsf.abmas.biz.
       30			PTR	hplj6f.abmas.biz.

   Example 3.14. DNS Abmas.biz Forward Zone File

       $ORIGIN .
       $TTL 38400      ; 10 hours 40 minutes
       abmas.biz       IN SOA  sleeth1.abmas.biz. root.abmas.biz. (
                                       2003021833 ; serial
                                       10800      ; refresh (3 hours)
                                       3600       ; retry (1 hour)
                                       604800     ; expire (1 week)
                                       38400      ; minimum (10 hours 40 minutes)
                                       )
                               NS      dns.abmas.biz.
                               MX      10 mail.abmas.biz.
       $ORIGIN abmas.biz.
       sleeth1                 A       192.168.1.1
       sleeth2                 A       192.168.2.1
       qmsa                    A       192.168.1.20
       hplj6a                  A       192.168.1.30
       qmsf                    A       192.168.2.20
       hplj6f                  A       192.168.2.30
       dns                     CNAME   sleeth1
       diamond                 CNAME   sleeth1
       mail                    CNAME   sleeth1

   Example 3.15. DNS Abmas.us Forward Zone File

       $ORIGIN .
       $TTL 38400      ; 10 hours 40 minutes
       abmas.us        IN SOA  server.abmas.us. root.abmas.us. (
                                       2003021833 ; serial
                                       10800      ; refresh (3 hours)
                                       3600       ; retry (1 hour)
                                       604800     ; expire (1 week)
                                       38400      ; minimum (10 hours 40 minutes)
                                       )
                               NS      dns.abmas.us.
                               NS      dns2.abmas.us.
                               MX      10 mail.abmas.us.
       $ORIGIN abmas.us.
       server                  A       123.45.67.66
       dns2                    A       123.45.54.32
       gw                      A       123.45.67.65
       www                     CNAME   server
       mail                    CNAME   server
       dns                     CNAME   server

4. All DNS name resolution should be handled locally. To ensure that the server is configured correctly to handle this, edit `/etc/resolv.conf` to have the following content:

       search abmas.us abmas.biz
       nameserver 127.0.0.1
       nameserver 123.45.54.23

   This instructs the name resolver function (when configured correctly) to ask the DNS server that is running locally to resolve names to addresses. In the event that the local name server is not available, ask the name server provided by the ISP. The latter, of course, does not resolve purely local names to IP addresses.

5. The final step is to edit the `/etc/nsswitch.conf` file. This file controls the operation of the various resolver libraries that are part of the Linux Glibc libraries. Edit this file so that it contains the following entries:

       hosts:      files dns wins

The basic DHCP and DNS services are now ready for validation testing. Before you can proceed, there are a few more steps along the road. First, configure the print spooling and print processing system. Then you can configure the server so that all services start automatically on reboot. You must also manually start all services prior to validation testing.

### Printer Configuration

Network administrators who are new to CUPS based-printing typically experience some difficulty mastering its powerful features. The steps outlined in this section are designed to navigate around the distractions of learning CUPS. Instead of implementing smart features and capabilities, our approach is to use it as a transparent print queue that performs no filtering, and only minimal handling of each print job that is submitted to it. In other words, our configuration turns CUPS into a raw-mode print queue. This means that the correct printer driver must be installed on all clients.

Procedure 3.4. Printer Configuration Steps

1. Configure each printer to be a DHCP client, carefully following the manufacturer's guidelines.

2. Follow the instructions in the printer manufacturer's manuals to permit printing to port 9100. Use any other port the manufacturer specifies for direct-mode raw printing, and adjust the port as necessary in the following example commands. This allows the CUPS spooler to print using raw mode protocols.

3. Configure the CUPS Print Queues as follows:

       root#  lpadmin -p qmsa -v socket://qmsa.abmas.biz:9100 -E
       root#  lpadmin -p hplj6a -v socket://hplj6a.abmas.biz:9100 -E
       root#  lpadmin -p qmsf -v socket://qmsf.abmas.biz:9100 -E
       root#  lpadmin -p hplj6f -v socket://hplj6f.abmas.biz:9100 -E

   This creates the necessary print queues with no assigned print filter.

4. Print queues may not be enabled at creation. Use `lpc stat` to check the status of the print queues and, if necessary, make certain that the queues you have just created are enabled by executing the following:

       root#  /usr/bin/enable qmsa
       root#  /usr/bin/enable hplj6a
       root#  /usr/bin/enable qmsf
       root#  /usr/bin/enable hplj6f

5. Even though your print queues may be enabled, it is still possible that they are not accepting print jobs. A print queue services incoming printing requests only when configured to do so. Ensure that your print queues are set to accept incoming jobs by executing the following commands:

       root#  /usr/sbin/accept qmsa
       root#  /usr/sbin/accept hplj6a
       root#  /usr/sbin/accept qmsf
       root#  /usr/sbin/accept hplj6f

6. Edit the file `/etc/cups/mime.convs` to uncomment the line:

       application/octet-stream     application/vnd.cups-raw      0     -

7. Edit the file `/etc/cups/mime.types` to uncomment the line:

       application/octet-stream

8. Printing drivers are installed on each network client workstation.

Note: If the parameter `cups options = Raw` is specified in the `smb.conf` file, the last two steps can be omitted with CUPS version 1.1.18, or later.

The UNIX system print queues have been configured and are ready for validation testing.

### Process Startup Configuration

There are two essential steps to process startup configuration. First, the process must be configured so that it automatically restarts each time the server is rebooted. This step involves use of the `chkconfig` tool that creates the appropriate symbolic links from the master daemon control file that is located in the `/etc/rc.d` directory, to the `/etc/rc'x'.d` directories. Links are created so that when the system run level is changed, the necessary start or kill script is run.

In the event that a service is not run as a daemon, but via the internetworking super daemon (`inetd` or `xinetd`), then the `chkconfig` tool makes the necessary entries in the `/etc/xinetd.d` directory and sends a hang-up (HUP) signal to the the super daemon, thus forcing it to re-read its control files.

Last, each service must be started to permit system validation to proceed.

1. Use the standard system tool to configure each service to restart automatically at every system reboot. For example,

       root#  chkconfig dhpcd on
       root#  chkconfig named on
       root#  chkconfig cups on
       root#  chkconfig smb on

2. Now start each service to permit the system to be validated. Execute each of the following in the sequence shown:

       root#  /etc/rc.d/init.d/dhcpd restart
       root#  /etc/rc.d/init.d/named restart
       root#  /etc/rc.d/init.d/cups restart
       root#  /etc/rc.d/init.d/smb restart

### Validation

Complex networking problems are most often caused by simple things that are poorly or incorrectly configured. The validation process adopted here should be followed carefully; it is the result of the experience gained from years of making and correcting the most common mistakes. Shortcuts often lead to basic errors. You should refrain from taking shortcuts, from making basic assumptions, and from not exercising due process and diligence in network validation. By thoroughly testing and validating every step in the process of network installation and configuration, you can save yourself from sleepless nights and restless days. A well debugged network is a foundation for happy network users and network administrators. Later in this book you learn how to make users happier. For now, it is enough to learn to validate. Let's get on with it.

Procedure 3.5. Server Validation Steps

1. One of the most important facets of Samba configuration is to ensure that name resolution functions correctly. You can check name resolution with a few simple tests. The most basic name resolution is provided from the `/etc/hosts` file. To test its operation, make a temporary edit to the `/etc/nsswitch.conf` file. Using your favorite editor, change the entry for `hosts` to read:

       hosts:     files

   When you have saved this file, execute the following command:

       root#  ping diamond
       PING sleeth1.abmas.biz (192.168.1.1) 56(84) bytes of data.
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=1 ttl=64 time=0.131 ms
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=2 ttl=64 time=0.179 ms
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=3 ttl=64 time=0.192 ms
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=4 ttl=64 time=0.191 ms

       --- sleeth1.abmas.biz ping statistics ---
       4 packets transmitted, 4 received, 0% packet loss, time 3016ms
       rtt min/avg/max/mdev = 0.131/0.173/0.192/0.026 ms

   This proves that name resolution via the `/etc/hosts` file is working.

2. So far, your installation is going particularly well. In this step we validate DNS server and name resolution operation. Using your favorite UNIX system editor, change the `/etc/nsswitch.conf` file so that the `hosts` entry reads:

       hosts:        dns

3. Before you test DNS operation, it is a good idea to verify that the DNS server is running by executing the following:

       root#  ps ax | grep named
         437 ?        S      0:00 /sbin/syslogd -a /var/lib/named/dev/log
         524 ?        S      0:00 /usr/sbin/named -t /var/lib/named -u named
         525 ?        S      0:00 /usr/sbin/named -t /var/lib/named -u named
         526 ?        S      0:00 /usr/sbin/named -t /var/lib/named -u named
         529 ?        S      0:00 /usr/sbin/named -t /var/lib/named -u named
         540 ?        S      0:00 /usr/sbin/named -t /var/lib/named -u named
        2552 pts/2    S      0:00 grep named

   This means that we are ready to check DNS operation. Do so by executing:

       root#  ping diamond
       PING sleeth1.abmas.biz (192.168.1.1) 56(84) bytes of data.
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=1 ttl=64 time=0.156 ms
       64 bytes from sleeth1 (192.168.1.1): icmp_seq=2 ttl=64 time=0.183 ms

       --- sleeth1.abmas.biz ping statistics ---
       2 packets transmitted, 2 received, 0% packet loss, time 999ms
       rtt min/avg/max/mdev = 0.156/0.169/0.183/0.018 ms

   You should take a few more steps to validate DNS server operation, as follows:

       root#  host -f diamond.abmas.biz
       sleeth1.abmas.biz has address 192.168.1.1

   You may now remove the entry called `diamond` from the `/etc/hosts` file. It does not hurt to leave it there, but its removal reduces the number of administrative steps for this name.

4. WINS is a great way to resolve NetBIOS names to their IP address. You can test the operation of WINS by starting `nmbd` (manually or by way of the Samba startup method shown in “Process Startup Configuration”). You must edit the `/etc/nsswitch.conf` file so that the `hosts` entry is as follows:

       hosts:        wins

   The next step is to make certain that Samba is running using `ps ax | grep mbd`. The `nmbd` daemon will provide the WINS name resolution service when the `smb.conf` file `` parameter wins support = Yes has been specified. Having validated that Samba is operational, excute the following:

       root#  ping diamond
       PING diamond (192.168.1.1) 56(84) bytes of data.
       64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.094 ms
       64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=0.479 ms

   Now that you can relax with the knowledge that all three major forms of name resolution to IP address resolution are working, edit the `/etc/nsswitch.conf` again. This time you add all three forms of name resolution to this file. Your edited entry for `hosts` should now look like this:

       hosts:       files dns wins

   The system is looking good. Let's move on.

5. It would give you peace of mind to know that the DHCP server is running and available for service. You can validate DHCP services by running:

       root#  ps ax | grep dhcp
        2618 ?        S      0:00 /usr/sbin/dhcpd ...
        8180 pts/2    S      0:00 grep dhcp

   This shows that the server is running. The proof of whether or not it is working comes when you try to add the first DHCP client to the network.

6. This is a good point at which to start validating Samba operation. You are content that name resolution is working for basic TCP/IP needs. Let's move on. If your `smb.conf` file has bogus options or parameters, this may cause Samba to refuse to start. The first step should always be to validate the contents of this file by running:

       root#  testparm -s
       Load smb config files from smb.conf
       Processing section "[homes]"
       Processing section "[printers]"
       Processing section "[netlogon]"
       Processing section "[profiles]"
       Processing section "[accounts]"
       Processing section "[service]"
       Processing section "[apps]"
       Loaded services file OK.
       # Global parameters
       [global]
           workgroup = PROMISES
           netbios name = DIAMOND
           interfaces = eth1, eth2, lo
           bind interfaces only = Yes
           passdb backend = tdbsam
           pam password change = Yes
           passwd program = /usr/bin/passwd '%u'
           passwd chat = *New*Password* %n\n \
                    *Re-enter*new*password* %n\n *Password*changed*
           username map = /etc/samba/smbusers
           unix password sync = Yes
           log level = 1
           syslog = 0
           log file = /var/log/samba/%m
           max log size = 50
           smb ports = 139
           name resolve order = wins bcast hosts
           time server = Yes
           printcap name = CUPS
           show add printer wizard = No
           add user script = /usr/sbin/useradd -m '%u'
           delete user script = /usr/sbin/userdel -r '%u'
           add group script = /usr/sbin/groupadd '%g'
           delete group script = /usr/sbin/groupdel '%g'
           add user to group script = /usr/sbin/usermod -G '%g' '%u'
           add machine script = /usr/sbin/useradd \
                                     -s /bin/false -d /dev/null '%u'
           shutdown script = /var/lib/samba/scripts/shutdown.sh
           abort shutdown script = /sbin/shutdown -c
           logon script = scripts\logon.bat
           logon path = \\%L\profiles\%U
           logon drive = X:
           logon home = \\%L\%U
           domain logons = Yes
           preferred master = Yes
           wins support = Yes
           utmp = Yes
           winbind use default domain = Yes
           map acl inherit = Yes
           cups options = Raw
           veto files = /*.eml/*.nws/*.{*}/
           veto oplock files = /*.doc/*.xls/*.mdb/

       [homes]
           comment = Home Directories
           valid users = %S
           read only = No
           browseable = No
       ...
       ### Remainder cut to save space ###

   Clear away all errors before proceeding.

7. Check that the Samba server is running:

       root#  ps ax | grep mbd
       14244 ?        S      0:00 /usr/sbin/nmbd -D
       14245 ?        S      0:00 /usr/sbin/nmbd -D
       14290 ?        S      0:00 /usr/sbin/smbd -D

       $rootprompt; ps ax | grep winbind
       14293 ?        S     0:00 /usr/sbin/winbindd -D
       14295 ?        S     0:00 /usr/sbin/winbindd -D

   The `winbindd` daemon is running in split mode (normal), so there are also two instances[7] of it.

8. Check that an anonymous connection can be made to the Samba server:

       root#  smbclient -L localhost -U%

               Sharename      Type      Comment
               ---------      ----      -------
               IPC$           IPC       IPC Service (Samba 3.0.20)
               netlogon       Disk      Network Logon Service
               profiles       Disk      Profile Share
               accounts       Disk      Accounting Files
               service        Disk      Financial Services Files
               apps           Disk      Application Files
               ADMIN$         IPC       IPC Service (Samba 3.0.20)
               hplj6a         Printer   hplj6a
               hplj6f         Printer   hplj6f
               qmsa           Printer   qmsa
               qmsf           Printer   qmsf

               Server               Comment
               ---------            -------
               DIAMOND              Samba 3.0.20

               Workgroup            Master
               ---------            -------
               PROMISES             DIAMOND

   This demonstrates that an anonymous listing of shares can be obtained. This is the equivalent of browsing the server from a Windows client to obtain a list of shares on the server. The `-U%` argument means to send a `NULL` username and a `NULL` password.

9. Verify that each printer has the IP address assigned in the DHCP server configuration file. The easiest way to do this is to ping the printer name. Immediately after the ping response has been received, execute `arp -a` to find the MAC address of the printer that has responded. Now you can compare the IP address and the MAC address of the printer with the configuration information in the `/etc/dhcpd.conf` file. They should, of course, match. For example,

       root#  ping hplj6
       PING hplj6a (192.168.1.30) 56(84) bytes of data.
       64 bytes from hplj6a (192.168.1.30): icmp_seq=1 ttl=64 time=0.113 ms

       root#  arp -a
       hplj6a (192.168.1.30) at 00:03:47:CB:81:E0 [ether] on eth0

   The MAC address `00:03:47:CB:81:E0` matches that specified for the IP address from which the printer has responded and with the entry for it in the `/etc/dhcpd.conf` file. Repeat this for each printer configured.

10. Make an authenticated connection to the server using the `smbclient` tool:

        root#  smbclient //diamond/accounts -U gholmes
        Password: XXXXXXX
        smb: \> dir
          .                          D        0  Thu Nov 27 15:07:09 2003
          ..                         D        0  Sat Nov 15 17:40:50 2003
          zakadmin.exe                   161424  Thu Nov 27 15:06:52 2003
          zak.exe                       6066384  Thu Nov 27 15:06:52 2003
          dhcpd.conf                       1256  Thu Nov 27 15:06:52 2003
          smb.conf                         2131  Thu Nov 27 15:06:52 2003
          initGrps.sh                A     1089  Thu Nov 27 15:06:52 2003
          POLICY.EXE                      86542  Thu Nov 27 15:06:52 2003

                        55974 blocks of size 65536. 33968 blocks available
        smb: \> q

11. Your new server is connected to an Internet-accessible connection. Before you start your firewall, you should run a port scanner against your system. You should repeat that after the firewall has been started. This helps you understand to what extent the server may be vulnerable to external attack. One way you can do this is by using an external service, such as the DSL Reports tools. Alternately, if you can gain root-level access to a remote UNIX/Linux system that has the `nmap` tool, you can run the following:

        root#  nmap -v -sT server.abmas.us

        Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
        Host server.abmas.us (123.45.67.66) appears to be up ... good.
        Initiating Connect() Scan against server.abmas.us (123.45.67.66)
        Adding open port 6000/tcp
        Adding open port 873/tcp
        Adding open port 445/tcp
        Adding open port 10000/tcp
        Adding open port 901/tcp
        Adding open port 631/tcp
        Adding open port 25/tcp
        Adding open port 111/tcp
        Adding open port 32770/tcp
        Adding open port 3128/tcp
        Adding open port 53/tcp
        Adding open port 80/tcp
        Adding open port 443/tcp
        Adding open port 139/tcp
        Adding open port 22/tcp
        The Connect() Scan took 0 seconds to scan 1601 ports.
        Interesting ports on server.abmas.us (123.45.67.66):
        (The 1587 ports scanned but not shown below are in state: closed)
        Port       State       Service
        22/tcp     open        ssh
        25/tcp     open        smtp
        53/tcp     open        domain
        80/tcp     open        http
        111/tcp    open        sunrpc
        139/tcp    open        netbios-ssn
        443/tcp    open        https
        445/tcp    open        microsoft-ds
        631/tcp    open        ipp
        873/tcp    open        rsync
        901/tcp    open        samba-swat
        3128/tcp   open        squid-http
        6000/tcp   open        X11
        10000/tcp  open        snet-sensor-mgmt
        32770/tcp  open        sometimes-rpc3

        Nmap run completed -- 1 IP address (1 host up) scanned in 1 second

    The above scan was run before the external interface was locked down with the NAT-firewall script you created above. The following results are obtained after the firewall rules have been put into place:

        root#  nmap -v -sT server.abmas.us

        Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
        Host server.abmas.us (123.45.67.66) appears to be up ... good.
        Initiating Connect() Scan against server.abmas.us (123.45.67.66)
        Adding open port 53/tcp
        Adding open port 22/tcp
        The Connect() Scan took 168 seconds to scan 1601 ports.
        Interesting ports on server.abmas.us (123.45.67.66):
        (The 1593 ports scanned but not shown below are in state: filtered)
        Port       State       Service
        22/tcp     open        ssh
        25/tcp     closed      smtp
        53/tcp     open        domain
        80/tcp     closed      http
        443/tcp    closed      https

        Nmap run completed -- 1 IP address (1 host up) scanned in 168 seconds

### Application Share Configuration

The use of an application server is a key mechanism by which desktop administration overheads can be reduced. Check the application manual for your software to identify how best to create an administrative installation.

Some Windows software will only run locally on the desktop computer. Such software is typically not suited for administrative installation. Administratively installed software permits one or more of the following installation choices:

- Install software fully onto a workstation, storing data files on the same workstation.

- Install software fully onto a workstation with central network data file storage.

- Install software to run off a central application server with data files stored on the local workstation. This is often called a minimum installation, or a network client installation.

- Install software to run off a central application server with data files stored on a central network share. This type of installation often prevents storage of work files on the local workstation.

A common application deployed in this environment is an office suite. Enterprise editions of Microsoft Office XP Professional can be administratively installed by launching the installation from a command shell. The command that achieves this is `setup /a`. It results in a set of prompts through which various installation choices can be made. Refer to the Microsoft Office Resource SDK and Resource Kit for more information regarding this mode of installation of MS Office XP Professional. The full administrative installation of MS Office XP Professional requires approximately 650 MB of disk space.

When the MS Office XP Professional product has been installed to the administrative network share, the product can be installed onto a workstation by executing the normal setup program. The installation process now provides a choice to either perform a minimum installation or a full local installation. A full local installation takes over 100 MB of disk space. A network workstation (minimum) installation requires typically 10 MB to 15 MB of local disk space. In the latter case, when the applications are used, they load over the network.

Microsoft Office Service Packs can be unpacked to update an administrative share. This makes it possible to update MS Office XP Professional for all users from a single installation of the service pack and generally circumvents the need to run updates on each network Windows client.

The default location for MS Office XP Professional data files can be set through registry editing or by way of configuration options inside each Office XP Professional application.

OpenOffice.Org OpenOffice Version 1.1.0 can be installed locally. It can also be installed to run off a network share. The latter is a most desirable solution for office-bound network users and for administrative staff alike. It permits quick and easy updates to be rolled out to all users with a minimum of disruption and with maximum flexibility.

The process for installation of administrative shared OpenOffice involves download of the distribution ZIP file, followed by extraction of the ZIP file into a temporary disk area. When fully extracted using the unzipping tool of your choosing, change into the Windows installation files directory then execute `setup -net`. You are prompted on screen for the target installation location. This is the administrative share point. The full administrative OpenOffice share takes approximately 150 MB of disk space.

#### Comments Regarding Software Terms of Use

Many single-user products can be installed into an administrative share, but personal versions of products such as Microsoft Office XP Professional do not permit this. Many people do not like terms of use typical with commercial products, so a few comments regarding software licensing seem important.

Please do not use an administrative installation of proprietary and commercially licensed software products to violate the copyright holders' property. All software is licensed, particularly software that is licensed for use free of charge. All software is the property of the copyright holder unless the author and/or copyright holder has explicitly disavowed ownership and has placed the software into the public domain.

Software that is under the GNU General Public License, like proprietary software, is licensed in a way that restricts use. For example, if you modify GPL software and then distribute the binary version of your modifications, you must offer to provide the source code as well. This restriction is designed to maintain the momentum of the diffusion of technology and to protect against the withholding of innovations.

Commercial and proprietary software generally restrict use to those who have paid the license fees and who comply with the licensee's terms of use. Software that is released under the GNU General Public License is restricted to particular terms and conditions also. Whatever the licensing terms may be, if you do not approve of the terms of use, please do not use the software.

Samba is provided under the terms of the GNU GPL Version 2, a copy of which is provided with the source code.

### Windows Client Configuration

Christine needs to roll out 130 new desktop systems. There is no doubt that she also needs to reinstall many of the notebook computers that will be recycled for use with the new network configuration. The smartest way to handle the challenge of the roll-out program is to build a staged system for each type of target machine, and then use an image replication tool such as Norton Ghost (enterprise edition) to replicate the staged machine to its target desktops. The same can be done with notebook computers as long as they are identical or sufficiently similar.

Procedure 3.6. Windows Client Configuration Procedure

1. Install MS Windows XP Professional. During installation, configure the client to use DHCP for TCP/IP protocol configuration. DHCP configures all Windows clients to use the WINS Server address that has been defined for the local subnet.

2. Join the Windows Domain `PROMISES`. Use the Domain Administrator username `root` and the SMB password you assigned to this account. A detailed step-by-step procedure for joining a Windows 200x/XP Professional client to a Windows Domain is given in “A Collection of Useful Tidbits”, “Joining a Domain: Windows 200x/XP Professional”. Reboot the machine as prompted and then log on using the Domain Administrator account (`root`).

3. Verify `DIAMOND` is visible in My Network Places, that it is possible to connect to it and see the shares accounts, apps, and finsvcs, and that it is possible to open each share to reveal its contents.

4. Create a drive mapping to the `apps` share on the server `DIAMOND`.

5. Perform an administrative installation of each application to be used. Select the options that you wish to use. Of course, you can choose to run applications over the network, correct?

6. Now install all applications to be installed locally. Typical tools include Adobe Acrobat, NTP-based time synchronization software, drivers for specific local devices such as fingerprint scanners, and the like. Probably the most significant application for local installation is antivirus software.

7. Now install all four printers onto the staging system. The printers you install include the accounting department HP LaserJet 6 and Minolta QMS Magicolor printers. You will also configure identical printers that are located in the financial services department. Install printers on each machine following the steps shown in the Windows client printer preparation procedure below.

8. When you are satisfied that the staging systems are complete, use the appropriate procedure to remove the client from the domain. Reboot the system and then log on as the local administrator and clean out all temporary files stored on the system. Before shutting down, use the disk defragmentation tool so that the file system is in optimal condition before replication.

9. Boot the workstation using the Norton (Symantec) Ghosting diskette (or CD-ROM) and image the machine to a network share on the server.

10. You may now replicate the image to the target machines using the appropriate Norton Ghost procedure. Make sure to use the procedure that ensures each machine has a unique Windows security identifier (SID). When the installation of the disk image has completed, boot the PC.

11. Log on to the machine as the local Administrator (the only option), and join the machine to the Domain, following the procedure set out in “A Collection of Useful Tidbits”, “Joining a Domain: Windows 200x/XP Professional”. The system is now ready for the user to log on, provided you have created a network logon account for that user, of course.

12. Instruct all users to log on to the workstation using their assigned username and password.

Procedure 3.7. Windows Client Printer Preparation Procedure

1. Click Start → Settings → Printers+Add Printer+Next. Do not click Network printer. Ensure that Local printer is selected.

2. Click Next. In the Manufacturer: panel, select `HP`. In the Printers: panel, select the printer called `HP LaserJet 6`. Click Next.

3. In the Available ports: panel, select `FILE:`. Accept the default printer name by clicking Next. When asked, “Would you like to print a test page?,” click No. Click Finish.

4. You may be prompted for the name of a file to print to. If so, close the dialog panel. Right-click HP LaserJet 6 → Properties → Details (Tab) → Add Port.

5. In the Network panel, enter the name of the print queue on the Samba server as follows: `\\DIAMOND\hplj6a`. Click OK+OK to complete the installation.

6. Repeat the printer installation steps above for both HP LaserJet 6 printers as well as for both QMS Magicolor laser printers.

### Key Points Learned

How do you feel? You have built a capable network, a truly ambitious project. Future network updates can be handled by your staff. You must be a satisfied manager. Let's review the achievements.

- A simple firewall has been configured to protect the server in the event that the ISP firewall service should fail.

- The Samba configuration uses measures to ensure that only local network users can connect to SMB/CIFS services.

- Samba uses the new `tdbsam` passdb backend facility. Considerable complexity was added to Samba functionality.

- A DHCP server was configured to implement dynamic DNS (DDNS) updates to the DNS server.

- The DNS server was configured to permit DDNS only for local network clients. This server also provides primary DNS services for the company Internet presence.

- You introduced an application server as well as the concept of cloning a Windows client in order to effect improved standardization of desktops and to reduce the costs of network management.

## Questions and Answers

1. What is the maximum number of account entries that the tdbsam passdb backend can handle?
2. Would Samba operate any better if the OS level is set to a value higher than 35?
3. Why in this example have you provided UNIX group to Windows Group mappings for only Domain Groups?
4. Why has a path been specified in the IPC$ share?
5. Why does the smb.conf file in this exercise include an entry for smb ports?
6. What is the difference between a print queue and a printer?
7. Can all MS Windows application software be installed onto an application server share?
8. Why use dynamic DNS (DDNS)?
9. Why would you use WINS as well as DNS-based name resolution?
10. What are the major benefits of using an application server?

1. | What is the maximum number of account entries that the `tdbsam` passdb backend can handle?

The tdb data structure and support system can handle more entries than the number of accounts that are possible on most UNIX systems. A practical limit would come into play long before a performance boundary would be anticipated. That practical limit is controlled by the nature of Windows networking. There are few Windows file and print servers that can handle more than a few hundred concurrent client connections. The key limiting factors that predicate offloading of services to additional servers are memory capacity, the number of CPUs, network bandwidth, and disk I/O limitations. All of these are readily exhausted by just a few hundred concurrent active users. Such bottlenecks can best be removed by segmentation of the network (distributing network load across multiple networks).

As the network grows, it becomes necessary to provide additional authentication servers (domain controllers). The tdbsam is limited to a single machine and cannot be reliably replicated. This means that practical limits on network design dictate the point at which a distributed passdb backend is required; at this time, there is no real alternative other than ldapsam (LDAP).

The guideline provided in TOSHARG2, Chapter 10, Section 10.1.2, is to limit the number of accounts in the tdbsam backend to 250. This is the point at which most networks tend to want backup domain controllers (BDCs). Samba-3 does not provide a mechanism for replicating tdbsam data so it can be used by a BDC. The limitation of 250 users per tdbsam is predicated only on the need for replication, not on the limits[8] of the tdbsam backend itself.

2. | Would Samba operate any better if the OS level is set to a value higher than 35?
| No. MS Windows workstations and servers do not use a value higher than 33. Setting this to a value of 35 already assures Samba of precedence over MS Windows products in browser elections. There is no gain to be had from setting this higher.
3. | Why in this example have you provided UNIX group to Windows Group mappings for only Domain Groups?
| At this time, Samba has the capacity to use only Domain Groups mappings. It is possible that at a later date Samba may make use of Windows Local Groups, as well as of the Active Directory special Groups. Proper operation requires Domain Groups to be mapped to valid UNIX groups.
4. | Why has a path been specified in the `IPC$` share?
| This is done so that in the event that a software bug may permit a client connection to the IPC$ share to obtain access to the file system, it does so at a location that presents least risk. Under normal operation this type of paranoid step should not be necessary. The use of this parameter should not be necessary.
5. | Why does the `smb.conf` file in this exercise include an entry for smb ports?

The default order by which Samba-3 attempts to communicate with MS Windows clients is via port 445 (the TCP port used by Windows clients when NetBIOS-less SMB over TCP/IP is in use). TCP port 139 is the primary port used for NetBIOS over TCP/IP. In this configuration Windows network operations are predicated around NetBIOS over TCP/IP. By specifying the use of only port 139, the intent is to reduce unsuccessful service connection attempts. The result of this is improved network performance. Where Samba-3 is installed as an Active Directory Domain member, the default behavior is highly beneficial and should not be changed.

6. | What is the difference between a print queue and a printer?

A printer is a physical device that is connected either directly to the network or to a computer via a serial, parallel, or USB connection so that print jobs can be submitted to it to create a hard copy printout. Network-attached printers that use TCP/IP-based printing generally accept a single print data stream and block all secondary attempts to dispatch jobs concurrently to the same device. If many clients were to concurrently print directly via TCP/IP to the same printer, it would result in a huge amount of network traffic through continually failing connection attempts.

A print server (like CUPS or LPR/LPD) accepts multiple concurrent input streams or print requests. When the data stream has been fully received, the input stream is closed, and the job is then submitted to a sequential print queue where the job is stored until the printer is ready to receive the job.

7. | Can all MS Windows application software be installed onto an application server share?

Much older Windows software is not compatible with installation to and execution from an application server. Enterprise versions of Microsoft Office XP Professional can be installed to an application server. Retail consumer versions of Microsoft Office XP Professional do not permit installation to an application server share and can be installed and used only to/from a local workstation hard disk.

8. | Why use dynamic DNS (DDNS)?
| When DDNS records are updated directly from the DHCP server, it is possible for network clients that are not NetBIOS-enabled, and thus cannot use WINS, to locate Windows clients via DNS.
9. | Why would you use WINS as well as DNS-based name resolution?

WINS is to NetBIOS names as DNS is to fully qualified domain names (FQDN). The FQDN is a name like “myhost.mydomain.tld” where `tld` means `top-level domain`. A FQDN is a longhand but easy-to-remember expression that may be up to 1024 characters in length and that represents an IP address. A NetBIOS name is always 16 characters long. The 16th character is a name type indicator. A specific name type is registered[9] for each type of service that is provided by the Windows server or client and that may be registered where a WINS server is in use.

WINS is a mechanism by which a client may locate the IP Address that corresponds to a NetBIOS name. The WINS server may be queried to obtain the IP Address for a NetBIOS name that includes a particular registered NetBIOS name type. DNS does not provide a mechanism that permits handling of the NetBIOS name type information.

DNS provides a mechanism by which TCP/IP clients may locate the IP address of a particular hostname or service name that has been registered in the DNS database for a particular domain. A DNS server has limited scope of control and is said to be authoritative for the zone over which it has control.

Windows 200x Active Directory requires the registration in the DNS zone for the domain it controls of service locator[10] records that Windows clients and servers will use to locate Kerberos and LDAP services. ADS also requires the registration of special records that are called global catalog (GC) entries and site entries by which domain controllers and other essential ADS servers may be located.

10. | What are the major benefits of using an application server?
| The use of an application server can significantly reduce application update maintenance. By providing a centralized application share, software updates need be applied to only one location for all major applications used. This results in faster update roll-outs and significantly better application usage control.

[5] See TOSHARG2, Chapter 3. This is necessary so that Samba can act as a Domain Controller (PDC); see TOSHARG2, Chapter 4, for additional information.

[6] You may want to do the echo command last and include "0" in the init scripts, since it opens up your network for a short time.

[7] For more information regarding winbindd, see TOSHARG2, Chapter 23, Section 23.3. The single instance of `smbd` is normal. One additional `smbd` slave process is spawned for each SMB/CIFS client connection.

[8] Bench tests have shown that tdbsam is a very effective database technology. There is surprisingly little performance loss even with over 4000 users.

[9] See TOSHARG2, Chapter 9, for more information.

[10] See TOSHARG2, Chapter 9, Section 9.3.3.

Prev | Up | Next
Chapter 2. Small Office Networking | Home | Chapter 4. The 500-User Office