Linux Operations and Administration Chapter Seventeen Networking in a Linux Environment

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

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

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

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

Figure 17-1 NIS communication with RPC © Cengage Learning 2013

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

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

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

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

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

Figure 17-2 The Network Information Service (NIS) Server Setup window © Cengage Learning 2013

Figure 17-3 The Master server Setup window © Cengage Learning 2013

Figure 17-4 The NIS Master Server Slaves Setup window © Cengage Learning 2013

Figure 17-5 Selecting NIS maps © Cengage Learning 2013

Figure 17-6 The NIS Server Query Hosts Setup window © Cengage Learning 2013

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

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

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

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

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

Figure 17-7 Configuring the NIS client © Cengage Learning 2013

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

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

Figure 17-8 The Expert settings window © Cengage Learning 2013

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

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

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

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

Figure 17-9 The Printer Configurations window © Cengage Learning 2013

Figure 17-10 The Print via Network window © Cengage Learning 2013

Figure 17-11 The Share Printers window © Cengage Learning 2013

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

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

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

Figure 17-12 Configuring dynamic DHCP settings © Cengage Learning 2013

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

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

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

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

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

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