Download Using Traditional Linux Printing: LPRng (continued)

Chapter 4:
server services
Objectives
• Configure network interfaces using commandline and graphical utilities
• Set up a simple DHCP server
• Manage networked printing services
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Configuring Linux Networking
• Learn more about
– Networking protocols
– Network configuration
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Understanding Network Devices
in Linux
• Linux networking devices
– Not shown in /dev directory
– Do not “exist” on system until appropriate device
driver installed in kernel
• Networking device
– Named channel over which network traffic can
pass
• Device drivers for networking are kernel modules
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Understanding Network Devices
in Linux (continued)
• Kernel modules can be loaded or unloaded while
Linux is running
• /dev/eth0
– First Ethernet card installed on system
• Media Access Control (MAC) address
– Unique address assigned by Ethernet card
manufacturer
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Understanding Network Devices
in Linux (continued)
• To obtain MAC address
– Host broadcasts message to entire network
segment using Address Resolution Protocol (ARP)
– Host with IP address responds directly to
computer that sent ARP request with MAC
address
– Source host stores MAC address and IP address
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Understanding Network Devices
in Linux (continued)
• arp command
– Display ARP cache
• Mapping of IP addresses to hardware addresses
– Used mainly for troubleshooting network
connectivity
– Refreshed frequently
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Configuring Networking with
Command-line Utilities (continued)
•
•
•
•
View status of interface: ifconfig eth0
Stop Ethernet interface: ifconfig eth0 down
Start Ethernet interface: ifconfig eth0 up
Routing table tells networking software where to
send packets that are not part of local network
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Configuring the DNS Resolver
• DNS
– Used to convert host and domain names into IP
addresses
– Implemented by server that supports DNS
• Reverse DNS converts IP address to domain
name
• Resolving
– Process of converting domain name to IP address
or vice versa
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Configuring the DNS Resolver
(continued)
• Resolver
– Client part of DNS
– Makes requests to DNS server
– Test by pinging another system using host name
instead of IP address
– Configured by file /etc/resolv.conf
– Contains IP address of one or more DNS servers
preceded by keyword nameserver
– Can include up to three DNS servers
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Configuring the DNS Resolver
(continued)
• Keyword
– Word to which program reading configuration file
attaches special meaning
• Utilities for researching DNS problems:
– dnsquery
– nslookup
– dig
– whois
– host
• /etc/hosts file stores IP addresses and
corresponding domain names in text file on host
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Dynamic Routing with Routing
Protocols
• Static routing
– Uses preconfigured routing table
– Not good choice for:
• Larger networks
• Unreliable connections
• Dynamic routing uses specialized routing
protocol to build and modify routing tables
automatically
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Dynamic Routing with Routing
Protocols (continued)
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Configuring a DHCP Server
• DHCP server installed by default on many Linux
systems
• /etc/dhcpd.conf file
– Configuration for DHCP
– Instructs DHCP server which IP address ranges
are available for DHCP clients
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Configuring a DHCP Server
(continued)
• When client requests IP address
:
– DHCP server leases address to client for specified
time
– At end of lease client must request new IP
address
– Whole arrangement transparent to user on client
host
• DHCP client can run on any operating system
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Networked Printing Services
• Linux includes network printing capabilities
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Using Traditional Linux Printing:
LPRng
• Traditional Linux printing system
• Based on version of UNIX
• Allows multiple users to print files at same
time to:
– Local printer
– Networked printers
• Print queues
– System administrator must define printers
– Printer definitions describe type of printer and
features to be used
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Using Traditional Linux Printing:
LPRng (continued)
• Printing file in LPRng system
– Application submits file to be printed (print job)
– Print job processed by print filter converts
information from Linux application into formatting
codes to produce desired output
– Printing utility stores print job in print spool
directory
• Default directory /var/spool/lpd
– Lpd print server program keeps track of all print
jobs in all print queues on system
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Using Traditional Linux Printing:
LPRng (continued)
• Correlation between print queue and physical
printer not always one to one
• Linux print filter
– Same as printer driver in other operating systems
– Converts documents or images into format that
printer can use
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Using Traditional Linux Printing:
LPRng (continued)
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Using Traditional Linux Printing:
LPRng (continued)
• Configuring local printer definitions
– Each LPRng printer definition created as print
queue entry in /etc/printcap configuration file
• Uses complex format
– Must provide appropriate Linux device name
• Parallel ports use device name lp followed by
device number
• Serial ports use name ttyS followed by device
number
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Printing Remotely Using LPRng
• Define printer on system that refers to remote
computer and print queue on remote system
– Key options in configuration file
• rm remote system specified
• rp remote print queue specified
• Once print job has been sent to remote system
using lpd, user has no direct control over it
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Managing Printing (continued)
• Alternatives command
• lpr command and lpc command
• Using lpc
– Prevent new print jobs from being accepted by
print queue
– Prevent print jobs from being sent to printer
– Cancel print job currently being printed
– See status of any printer
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Managing Printing (continued)
• lpq utility lists each print job in print queue with
status information
• lprm command deletes print job from queue
• Graphical print management utilities
– Print Manager
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