[Chapter 13] Internet Information Resources
some other browsers this field is labeled "Location" or "Netsite," but in all cases it performs the same
function: it holds the path to the information resource. In the example the location is
"URL" stands for universal resource locator. It is a standard way of
defining a network resource and it has a specific structure:
service://server/path/file
In the sample URL, http is the service; csrc.nist.gov is the server; and secalerts is the path to the
resource contained on that server. This tells the browser to locate a host with the domain name
csrc.nist.gov, and to ask it for the hypertext information located in the secalerts path. Hypertext is not
the only type of information that can be retrieved by a browser. The browser is intended to provide a
consistent interface to various types of network resources. HTTP is only one of the services that can
be specified in a URL.
A Web browser can be used to view local hypertext files. This is how the gated documentation is
delivered.
Figure 13.2 shows a network administrator reading the gated documentation. The URL in
Figure 13.2 is file://localhost/usr/doc/config_guide/config.html. The service is file, which means that
the resource is to be read via the standard filesystem. The server is the local host (localhost). The path
is /usr/doc/config_gated, and the file is config.html.
Figure 13.2: Reading GateD documentation
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[Chapter 13] Internet Information Resources
Another browser service that is often used by a network administrator is FTP. Figure 13.3 shows a
network administrator using a browser to download software. The URL in
Figure 13.3 is
FTP is the service used to access the resource,
which in this case is a binary file. The server is ftp.ncsa.edu, which is the anonymous FTP server at
the National Center for Super Computing Applications. The path is /Web/Mosaic/Unix/binaries/2.6
and the file is any of the files listed on the screen.
Figure 13.3: Browser FTP interface
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Resources
Next: 13.3 Finding Files

13.2 Anonymous FTP
Anonymous FTP is mentioned throughout this book as a technique for retrieving publicly available
files and programs from the many FTP servers around the Internet. Anonymous FTP is simply an ftp
session in which you log into the remote server using the username anonymous and, by convention,
your email address as the password. [1] The anonymous FTP example below should make this simple
process clear:
[1] Some FTP servers request your real username as a password.
% ftp ftp.ncsa.edu
Connected to ftp.ncsa.uiuc.edu.
220 FTP server Wed May 21 1997 ready.
Name (ftp.ncsa.edu:kathy): anonymous
331 Guest login ok, use email address as password.
Password:
ftp> cd /Web/Mosaic/Unix/binaries/2.6
250 CWD command successful.
ftp> binary
200 Type set to I.
ftp> get Mosaic-hp-2.6.Z Mosaic.Z
200 PORT command successful.
150 Opening BINARY mode data connection for Mosaic-hp-2.6.Z.
226 Transfer complete.
local: Mosaic.Z remote: Mosaic-hp-2.6.Z
809343 bytes received in 3.5 seconds (2.3e+02 Kbytes/s)
ftp> quit
221 Goodbye.
In this example, the user logs into the server ftp.ncsa.edu using the username anonymous and the
password , which is her email address. With anonymous FTP, she can log in even

# mkdir etc
# mkdir pub
Then copy ls to /usr/ftp/bin, and set the correct permissions.
# cp /bin/ls /usr/ftp/bin
# chmod 111 /usr/ftp/bin/ls
Create a group that will be used only by anonymous FTP, a group that has no other members. In our
example we create a group called anonymous. An entry for this new group is added to the /etc/group
file, and a file named /usr/ftp/etc/group is created that contains only this single entry.
anonymous:*:15:
Create a user named ftp by placing an entry for that user in the file /etc/passwd. Also create a file
named /usr/ftp/etc/passwd that contains only the ftp entry. Here's the entry we used in both files:
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[Chapter 13] 13.2 Anonymous FTP
ftp:*:15:15:Anonymous ftp:/usr/ftp:
These examples use a GID of 15 and a UID of 15. These are only examples; pick a UID and GID that
aren't used for anything else on your system.
A cat of the newly created /usr/ftp/etc/passwd and /usr/ftp/etc/group files shows the following:
% cat /usr/ftp/etc/passwd
ftp:*:15:15:Anonymous ftp:/usr/ftp:
% cat /usr/ftp/etc/group
anonymous:*:15:
After the edits are complete, set both files to mode 444:
# chmod 444 /usr/ftp/etc/passwd
# chmod 444 /usr/ftp/etc/group
Set the correct ownership and mode for each of the directories. The ownership of /usr/ftp/pub,
/usr/ftp/bin, and /usr/ftp/etc do not need to be changed because the directories were created by root.
# cd /usr/ftp
# chmod 644 pub
# chmod 555 bin

# cd /usr/ftp
# mkdir dev
# cd dev
# mknod zero c 3 12
# cd ..
# chmod 555 dev
Now you can copy the files you wish to make publicly available into /usr/ftp/pub. To prevent these
files from being overwritten by remote users, set the mode to 644 and make sure the files are not
owned by user ftp.
Once you complete the configuration steps necessary for your system, test it thoroughly before
announcing the service. Make sure that your server provides the anonymous FTP service you want,
without providing additional "services" that you don't want (such as allowing anonymous users access
to files outside of the ftp home directory). Anonymous FTP is a potential security risk. If you offer
this service at all, limit the number of systems at your site that provide it (one is usually enough), and
take care to ensure that the installation is done properly.
Previous: 13.1 The World
Wide Web
TCP/IP Network
Administration
Next: 13.3 Finding Files
13.1 The World Wide Web
Book Index
13.3 Finding Files
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[Chapter 13] 13.3 Finding Files
Previous: 13.2 Anonymous
FTP
Chapter 13

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[Chapter 13] 13.3 Finding Files
There are many interactive archie commands, but the basic function of locating a program that is
accessible via anonymous FTP can be reduced to two commands.
prog pattern
Display all files in the database with names that match the specified pattern.
mail address
Mail the output of the last command to address, which is normally your own email address.
The following example uses both of these commands to interactively search for gated-R3_5_5.tar,
and then mail the results of the search to
% telnet archie.internic.net
Trying 198.49.45.10...
Connected to archie.ds.internic.net.
Escape character is ']'.
UNIX(r) System V Release 4.0 (ds0)
login: archie

# Bunyip Information Systems, Inc., 1993, 1994, 1995

archie> prog gated-R3_5_5.tar
# Search type: sub.
# Your queue position: 1
# Estimated time for completion: 5 seconds.
working... O
Host ftp.zcu.cz (147.228.206.16)
Last updated 11:32 27 Jun 1997
Location: /pub/security/merit/gated
FILE -r--r--r-- 1460773 bytes Jan 1997 gated-R3_5_5.tar.gz
archie> mail

example, assume we rerun the search for gated-R3_5_5.tar.gz using the
Web page. The server returns a list of eight matches, the first of
which is the anonymous FTP server at ftp.zcu.cz. The filename gated-R3_5_5.tar.gz that is displayed
next to the FTP server is a link. Clicking on the link transfers the file from ftp.zcu.cz to your system.
Search and retrieval all in one interface!
While the Web browser provides the easiest interface to archie, some people prefer to run an archie
client on their local system. Using an archie client reduces the load on the servers and improves
responsiveness for the user. If you believe you'll access archie very frequently, it might be worth
setting up an archie client.
13.3.1.1 archie client software
archie client software is available via anonymous FTP from the ftp.bunyip.com server. The software
is stored in the pub/archie/clients directory. The README file in this directory provides a short
description of each type of client. There are at least three different client software packages for UNIX:
an X windows client and two command-line clients, one written in C and the other written in Perl.
Check the archie servers for the latest developments in client software.
This section uses the command-line archie client written in C as an example. The C code and the
instruction to make the client are all contained in the c-archie-1.4.1.tar.gz file from ftp.bunyip.com.
Once the client has been made and installed, it is invoked using the command:
% archie [options] string
The string is the name of the file that you are asking archie to find. It can be the exact filename, a
substring of the name, or a regular expression.
The options control how the string is interpreted. The -e option searches for a filename that exactly
matches the string; the -s option matches on any record that contains the string as any part of the
filename; and the -r option interprets the string as a UNIX regular expression when looking for
matches.
The following example uses the archie client to search for sites from which the ppp software can be
retrieved. The search uses a regular expression that will match any compressed tar file with a name
that starts with ppp.
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Throughout this book, we have referred to many RFCs. These are the Internet documents used for
everything from general information to the definitions of the TCP/IP protocols standards. As a
network administrator, there are several important RFCs that you'll want to read. In this section we
describe how you can obtain them.
RFCs are available via the World Wide Web at
. Follow the links from that
home page through the directory services to the IETF RFC page. The page allows you to search the
RFCs for keywords or to load the RFC index. The index is particularly useful if you know the number
of the RFC you want.
Figure 13.5 shows a network administrator scrolling through the index looking
for RFC 1122.
Figure 13.5: The RFC index
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[Chapter 13] 13.4 Retrieving RFCs
In another example the network administrator does not know which RFCs contain the information she
is looking for, but she knows what she wants. The administrator is trying to find out more about the
SMTP service extensions that have been proposed for Extended SMTP.
Figure 13.6 shows the four
RFCs displayed as a result of her query.
Figure 13.6: An RFC Web search
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[Chapter 13] 13.4 Retrieving RFCs
The Web provides the most popular and best method for browsing through RFCs. However, if you
know what you want, anonymous FTP can be a faster way to retrieve a specific document. RFCs are
stored at ds.internic.net in the rfc directory. It stores the RFCs with filenames in the form rfcnnnn.txt
or rfcnnnn.ps, where nnnn is the RFC number and txt or ps indicates whether the RFC is ASCII text or
PostScript. To retrieve RFC 1122, ftp to ds.internic.net and enter get rfc/rfc1122.txt at the ftp>
prompt. This is generally a very quick way to get an RFC, if you know what you want.

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[Chapter 13] 13.5 Mailing Lists
Previous: 13.4 Retrieving
RFCs
Chapter 13
Internet Information
Resources
Next: 13.6 The White Pages

13.5 Mailing Lists
Mailing lists bring together people with similar interests to exchange information and ideas. Most mailing
lists run under usage guidelines that restricted discussion to a specific topic. Mailing lists are often used as
places to report problems and get solutions, or to receive announcements. Some mailing lists are digests of
newsgroups.
There is an enormous number of mailing lists. The list-of-lists contains information about many of the
mailing lists that are of interest to network administrators. [4] Use a Web browser to search for mailing lists
that interest you at
If you prefer, the list-of-lists can be
downloaded via anonymous FTP from nisc.sri.com in the file netinfo/interest-groups.txt and searched with
standard UNIX tools. Either way, you get the same information. The following example is the list-of-lists
entry for the Berkeley Internet Name Domain (BIND) software mailing list:
[4] Despite its large size, not every network administration mailing list is contained in the
interest-groups.txt file. You hear about some lists by word of mouth.

Subscription Address:
Owner:
Description:
This list covers topics relating to Berkeley Internet Name Domain

be stored on the local system until it is read. Thus, if there are 100 people on a list, 100 messages are sent
over the network and stored at 100 receiving systems. Network news provides a more efficient method for
distributing this kind of information. The information is stored around the network on, for most sites, one or
two news servers. Therefore, instead of moving mail messages to every individual on your network who
wants to discuss the Linux operating system, news articles about Linux are stored at one location where they
can be read when the user is ready. Not only does this reduce the network load, it reduces the number of
redundant copies that are stored on local disk files.
Network news is delivered over TCP/IP networks using the Network News Transfer Protocol (NNTP).
NNTP is included as part of the TCP/IP protocol stack on most UNIX systems and requires no special
configuration. The only thing you need to know to get started is the name of your closest network news
server. Ask your ISP. Most ISPs provide network news as part of their basic service.
NNTP is a simple command/response protocol. The NNTP server listens to port 119:
% telnet news.nuts.com 119
Trying 172.16.16.19...
Connected to news.nuts.com.
Escape character is ']'.
200 news.nuts.com ready (posting ok).
quit
205
Connection closed by foreign host.
A help command sent to this server would have produced a list of 23 NNTP commands. Luckily this is not
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[Chapter 13] 13.5 Mailing Lists
how you read network news. You use a newsreader.
UNIX systems often include a news reader. Our sample Linux system includes several different readers: nn,
rn, tin, and trn. Your system may have anyone one of these or another newsreader. See the appropriate
manpage for specific instructions on using a particular reader.
Regardless of the reader you have, they all have certain things in common. They all provide a way to
subscribe to a news group, read articles from the group, and post your own articles to the group. In this trn

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