1. Linux Operations and Administration
Chapter Seventeen
Networking in a Linux Environment

2. Objectives Describe key functions of the Network Information Service
Install and configure an NIS server and client
Configure a local printer queue
Install and configure a DHCP server

3. Network Information Service
Network Information Service (NIS)
A client/server protocol that centralizes user and group IDs
Provides database access so that network computers can share configuration information
Such as contents of /etc/passwd, /etc/shadow, and /etc/group files
Maps
Databases that store shared configuration information related to NIS networks

4. Network Information Service (cont’d.)
NIS setup consists of three types of host servers:
NIS master server
Contains NIS maps and makes them available over the network
NIS slave servers
Can be used to distribute NIS master server’s load more evenly
NIS clients
All hosts in an NIS-based network, including master and slave servers

5. Network Information Service (cont’d.)
NIS domain determines which NIS server should process the client request
NIS uses Remote Procedure Calls (RPC) technology
Standard method of allocating and managing shared resources between NIS clients and servers
For NIS to operate correctly, RPC portmapper must run on both NIS client and server

6. Figure 17-1 NIS communication with RPC
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7. Installing and Configuring NIS Servers
To install NIS, you need to have both NIS server and client
Decide whether computer will be used as a master server, a slave server, or a client
If an NIS server (master or slave) is already installed on Linux network:
Need to install only the NIS client
If there are no NIS servers on Linux network:
Need to install the server as well as the client

8. Installing and Configuring NIS Servers (cont’d.)
Before configuring system for use as an NIS server or client, provide a domain name for the computer
Done to ensure that a client and server in the same domain can communicate with each other
A client can’t access a server in a different domain

9. Creating an NIS Domain domainname command
Can be used to create an NIS domain
Must be issued from root user account when setting a domain name
To save NIS domain name permanently:
Edit runlevel script /etc/init.d/network
Specify NIS domain name in the script
Example: # Set the NIS domain name domainname example

10. Installing an NIS Master Server
NIS master server contains source files for all NIS maps in a domain
OpenSUSE
Provides an NIS client by default
Need to install an NIS server
yast2 -i yast2-nis-server command
Used to download and install nis-server RPM package and dependencies
Works from root user account

11. Configuring an NIS Master Server in YaST
yast2 nis-server command
Used to start YaST NIS Server module
Opening window of module shows the current status of NIS server
Master Server Setup window
NIS Master Server Slaves Setup window
NIS Server Maps Setup window
NIS Server Query Hosts Setup window

12. Figure 17-2 The Network Information Service (NIS) Server Setup window
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13. Figure 17-3 The Master server Setup window
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14. Figure 17-4 The NIS Master Server Slaves Setup window
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15. Figure 17-5 Selecting NIS maps
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16. Figure 17-6 The NIS Server Query Hosts Setup window
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17. Configuring an NIS Master Server Manually
After NIS server and client are installed, /var/yp/ directory is created on the same computer to store all NIS maps
Each NIS map consists of two files:
Index
Contains key values (also called “indices”) of an NIS map arranged in hash order
Has a .dir extension
Data
Contains actual data related to a key value
Has a .pag extension

18. Configuring an NIS Master Server Manually (cont’d.)
Table 17-1
Describes some commonly used NIS maps
After NIS Server module is started, NIS exports data to /var/yp directory
/var/yp/Makefile
A NIS configuration file in /var/yp directory
Can be run with make file command
This command can be issued only from /var/yp directory
Used to push updated maps to NIS slave server

19. Configuring an NIS Master Server Manually (cont’d.)
Table 17-1 Common NIS maps

20. Configuring an NIS Master Server Manually (cont’d.)
/var/yp/securenets
A NIS configuration file in /var/yp directory
Specifies NIS clients’ access rights to NIS server
Activity 17-1: Installing and Configuring an NIS Server
Install and configure an NIS server in YaST

21. Installing and Configuring NIS Clients
YaST NIS Client module is packaged with latest version of openSUSE
To start NIS Client module, use yast2 nis-client command
Activate NIS by clicking Use NIS option button
Define NIS policy to specify how NIS configuration will be modified
Default: it’s handled by netconfig script
Only Manual Changes option
Custom Policy option

22. Figure 17-7 Configuring the NIS client
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23. Installing and Configuring NIS Clients (cont’d.)
Netconfig is a modular tool for managing network configuration settings
Need to specify NIS domain
Enter NIS server IP address
Broadcast check box
Start Automounter check box

24. Installing and Configuring NIS Clients (cont’d.)
Open Port in Firewall check box
Can use Expert button to open Expert settings window
Answer Remote Hosts setting
Broken server setting
Activity 17-2: Configuring an NIS Client
Configure an NIS client in YaST

25. Figure 17-8 The Expert settings window
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26. Managing Other Network Services
Linux provides network services for managing many important administrative tasks
Two of the essential network tasks:
Manage print queues
Manage IP addresses on a network

27. Network Printing in Linux
Common UNIX Printing System (CUPS)
Provides a printing interface on a local network
CUPS software converts many different types of files into data a printer can understand and process
CUPS software referred to as a filter
Enables CUPS to print to a wide variety of printers
Printer device
Physical printer that transfers a print job from a computer to actual hard copy

28. Network Printing in Linux (cont’d.)
Printer driver
Software used to manage the printer device
Print queue
A directory file where the printer daemon can store print jobs
Multiple users can use the same printer device
YaST Printer Configurations module
Used to set up local or remote printer queues

29. Network Printing in Linux (cont’d.)
Remote printer queue
Located on another host in the network, not on your local computer
You can access and use remote printer queues, but can’t modify them from your local computer
yast2 printer command
Used to start YaST Printer Configurations module

30. Figure 17-9 The Printer Configurations window
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31. Figure 17-10 The Print via Network window
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32. Figure 17-11 The Share Printers window
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33. Overview of DHCP in Linux
Used to assign IP addresses automatically for each network host
You don’t have to configure each host separately
Can be used to configure other network client settings, such as:
Setting up name server entries in /etc/resolv.conf file
Configuring host gateway information

34. Overview of DHCP in Linux (cont’d.)
Table 17-2
Describes some identifying information that DHCP provides
DHCP server leases IP addresses for a period you specify and assigns them to client computers dynamically
Useful when not all computers in a network stay connected permanently

35. Configuring a DHCP Server
YaST DHCP module
Not included with openSUSE
You have to install DNS/DHCP pattern
yast2 dhcp-server command
Used to start DHCP module

36. Figure 17-12 Configuring dynamic DHCP settings
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37. Configuring a DHCP Server (cont’d.)
Settings you can make in each window:
Card Selection
Select NICs for DHCP server
Open the firewall to allow access to DHCP server from remote computers
Global Settings
Configure settings such as domain name, primary and secondary name servers’ IP addresses, default gateway, and WINS server IP address

38. Configuring a DHCP Server (cont’d.)
Dynamic DHCP
Review subnet information, such as network and netmask addresses
Configure IP address range and lease time
Start-up
Specify that DHCP server starts automatically when your Linux machine boots

39. Configuring a DHCP Server (cont’d.)
Expert configuration mode
Can be used to fine-tune settings for DHCP server
Host Management window
Can be used to configure static allocation
A host can be assigned the same IP address every time it connects to the network

40. Summary
Network Information Service is a client/server protocol that centralizes user and group IDs
NIS master server contains source files for all NIS maps in a domain and makes them available
Installing NIS server also installs NIS client
NIS slave servers are used to distribute the master server’s load more evenly
All hosts in an NIS network are called NIS clients
domainname command is used to display or temporarily specify NIS domain name

41. Summary (cont’d.)
yast2 -i yast2-nis-server command is used to install YaST NIS Server module
Module started with yast2 nis-server command
NIS maps are multicolumn database files storing key/value pairs that provide fast database access
YaST Printer Configurations module uses printer daemons, such as CUPS, for setting up a local or network printer
Module started with yast2 printer command

42. Summary (cont’d.)
CUPS provides a printing interface on a local network that’s used to convert files into data a printer can process
Printer device is the physical printer that transfers a print job from a computer to actual hard copy
A printer driver is the software used to manage a printer device
DHCP is used to assign IP addresses automatically for each network host
Module started with yast2 dhcp-server command