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host in Berlin that belongs to the ISP somehow. Looking at a map of Germany, you might be able to guess that hops 6 and 7 went via Hanover, and hop 8 was in Düsseldorf. That's apparently also where the cable across the big pond starts, because hops 9 and 10 were quite likely in New York City. 11 seems to be Chicago, and 16 to 18 could be San Francisco. That makes sense, given that O'Reilly's headquarters (and therefore the likely location of the machine www.oreilly.com/www.oreillynet.com) is in California.

dig

dig is the last diagnostic utility we cover in this section. dig is a utility that queries DNS servers and returns the information held about a particular domain. Let's start with an example right away:

kalle@tigger:~> dig oreilly.com

; <<>> DiG 9.3.1 <<>> oreilly.com

;; global options: printcmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52820

;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 0

;; QUESTION SECTION:

;oreilly.com. IN A

;; ANSWER SECTION:

oreilly.com. 21600 IN A 208.201.239.36

oreilly.com. 21600 IN A 208.201.239.37

;; AUTHORITY SECTION:

oreilly.com. 21600 IN NS ns2.sonic.net.

oreilly.com. 21600 IN NS ns.oreilly.com.

oreilly.com. 21600 IN NS ns1.sonic.net.

;; Query time: 252 msec

;; SERVER: 195.67.199.9#53(195.67.199.9)

;; WHEN: Wed Jul 6 13:31:02 2005

;; MSG SIZE rcvd: 123

Now what does this tell you? Have a look at the ANSWER SECTION. It tells you the IP addresses in use by the domain name service serving the domain oreilly.com. If you have a problem resolving addresses in this domain, you could try to ping these addresses to see whether the problem is actually with O'Reilly's DNS and not your own. The AUTHORITY SECTION gives you information about the so-called authoritative nameservers for this domain—the ones that are supposed to always give you the correct answer. It is good network administration practice to have at least two, and preferably three, of them, and to have them in different networks, so that the DNS service still works when one of them is down.

The third line from the bottom tells you the nameserver that was used to perform the DNS query; this is taken from your own setup. You can use this information to see whether you have entered the correct information in your DNS setup.

You can also specify a particular nameserver to query. For example, if you wanted to use the nameserver running at 195.67.199.10 instead, you could use:

dig @195.67.199.10 oreilly.com

Normally, you should get exactly the same result, but if you get a result at all from one of them but not from the other, then it's likely that the one not responding is simply down, or, per your network configuration, not reachable.

* * *

[*] Computer users are using ping as a verb these days.

[*] While the author was remotely logged in via ssh from Sweden, thanks to the Internet.

Chapter 14. Printing

The paperless society has not yet come to pass, and it now seems more likely that we'll just move from conventional paper to electronic paper. Until that time comes, you'll need to communicate with many people by putting your computer documents on bleached dead trees.

Because many distributions set up printing for you, we start this chapter with an introduction to command-line utilities you can use for printing and printer control. Then we'll explain how to configure printing on both local and network printers, focusing on the simple and powerful Common Unix Printing System (CUPS ).

Printing

Linux provides various user-level printing options. Traditionally, tools such as the text-mode lpr have been used to print files from the command line. Understanding how to use these and other printing and document formatting commands will enable you to print documents quickly and efficiently. A quick rundown of the enscript and nenscript utilities will help you create good-looking printouts even from basic text documents. GUI programs present their own user interfaces that you can use to control printing options from such programs.