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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 Linux Operations and Administration 2 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 Linux Operations and Administration 3 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 Linux Operations and Administration 4 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 Linux Operations and Administration 5 Figure 17-1 NIS communication with RPC © Cengage Learning 2013 Linux Operations and Administration 6 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 Linux Operations and Administration 7 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 Linux Operations and Administration 8 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 Linux Operations and Administration 9 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 Linux Operations and Administration 10 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 Linux Operations and Administration 11 Figure 17-2 The Network Information Service (NIS) Server Setup window © Cengage Learning 2013 Linux Operations and Administration 12 Figure 17-3 The Master server Setup window © Cengage Learning 2013 Linux Operations and Administration 13 Figure 17-4 The NIS Master Server Slaves Setup window © Cengage Learning 2013 Linux Operations and Administration 14 Figure 17-5 Selecting NIS maps © Cengage Learning 2013 Linux Operations and Administration 15 Figure 17-6 The NIS Server Query Hosts Setup window © Cengage Learning 2013 Linux Operations and Administration 16 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 Linux Operations and Administration 17 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 Linux Operations and Administration 18 Configuring an NIS Master Server Manually (cont’d.) Table 17-1 Common NIS maps Linux Operations and Administration 19 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 Linux Operations and Administration 20 Installing and Configuring NIS Clients • YaST NIS Client module is packaged with latest version of openSUSE • To start NIS Client module, use yast2 nisclient 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 Linux Operations and Administration 21 Figure 17-7 Configuring the NIS client © Cengage Learning 2013 Linux Operations and Administration 22 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 Linux Operations and Administration 23 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 Linux Operations and Administration 24 Figure 17-8 The Expert settings window © Cengage Learning 2013 Linux Operations and Administration 25 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 Linux Operations and Administration 26 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 Linux Operations and Administration 27 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 Linux Operations and Administration 28 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 Linux Operations and Administration 29 Figure 17-9 The Printer Configurations window © Cengage Learning 2013 Linux Operations and Administration 30 Figure 17-10 The Print via Network window © Cengage Learning 2013 Linux Operations and Administration 31 Figure 17-11 The Share Printers window © Cengage Learning 2013 Linux Operations and Administration 32 Overview of DHCP in Linux • DHCP – 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 Linux Operations and Administration 33 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 Linux Operations and Administration 34 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 Linux Operations and Administration 35 Figure 17-12 Configuring dynamic DHCP settings © Cengage Learning 2013 Linux Operations and Administration 36 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 Linux Operations and Administration 37 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 Linux Operations and Administration 38 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 Linux Operations and Administration 39 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 Linux Operations and Administration 40 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 Linux Operations and Administration 41 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 Linux Operations and Administration 42