Cover V02, I01


Questions and Answers

Bjorn Satdeva

LISA VI Conference

The USENIX LISA VI system administration conference is now over. A number of good papers were presented, but, as always, many of the highlights of the conference came in the course of social contacts between system administration peers in the hallways and bars of the conference hotel. Except for those at very large sites, system administrators usually have no peers at work. Users may be friends, but they cannot be peers, because their perspectives and needs are so different from the system administrator's.

Among the interesting papers presented were Paul Anderson's "Effective Use of Local Workstation Disks in an NFS Network," Peg Shafer's "Is Centralized System Administration the Answer?" Carol Kubicki's "Customer Satisfaction, Metrics and Measurement," and Richard Elling and Matthew Long's "user-setup: A System for Custom Configuration of User Environments, or Helping Users Help Themselves." Most interesting to me was Michael A. Cooper's "Overhauling Rdist for the '90s," a description of a new version of rdist, which was first introduced in 4.3 BSD UNIX. This version promises to fix many of the problems in the original rdist that had to do with large-scale distribution.

LISA VII in 1993

Although LISA VI is barely over, the work on next year's LISA conference, to take place November 1-5 in Monterey, California, is already underway. The Call for Papers will be out before the USENIX Winter conference in January, but in the meantime, here's a little taste of what we are working on. The topic, "The Human Aspect of UNIX System Administration," reflects the fact that system administrators have come to recognize that providing good support is not only a technical task, but also one which requires dealing with human beings. This is not to say that LISA will become an amateur psychology gathering. What we hope for is submissions that deal practically with management of the human aspect -- through policies, procedures, and improved forms of communication. Of course, traditional technical papers will be welcomed in the usual fashion.

The Interop Exhibition

The Interop exhibition, one of the major tradeshows in the UNIX community, took place in San Francisco the week after LISA VI. The fact that this show has grown so much must be proof of the commercial success of UNIX. This year was the first in San Francisco -- the show had been in San Jose, in the heart of Silicon Valley, in previous years.

The size of the show is now almost intimidating, and it's packed with vendors who claim to have all the solutions to one's problems, if one will only purchase their application. While many vendors did indeed have good solutions to some of the problems, the oft-repeated claim of having the one and only solution served to heighten my natural skepticim. Taken in moderation, however, the show is a very good source of information. I decided ahead of time to focus on low-priced routers, and was able to obtain some good information in this area.

The routers provided by well-known companies such as Cisco and Wallfleet are all of the high-performance kind and are priced accordingly. I was looking for alternatives, capable of performing well enough for a slip connection or a 56Kbit lease line and priced within reason for smaller companies. I found a couple of possible solutions.

One of the most facinating possibilities was a T1 radio-wave solution from Cylink. Using this kind of technology, you pay only the setup cost and the cost to the Internet service provider, but no cost for leased lines from the phone company. Cylink claims that this technology works up to a distance of 10 miles, with very slight deterioration in bad weather.

Network Application Technology showed an IP router, the LANB/290 Remote IP Router, which seems to qualify as one as the lowest-priced routers on the market. Each router comes with a LAN connection, one console port, and a data link connection for RS-232, RS-449/422, V.35, or X.21. It uses the PPP over the serial link, and will support SNMP.

CMC Network Products unit of Rockwell International presented the Net Hopper, a dialup TCP/IP router, which seems to be positioned as competiton to the NetBlazer from Telebit. With the modem(s) built in, the Net Hopper is very competitively priced at $2,000 with one modem and one LAN connection, or $3,500 with one LAN and three modems. CMC claims that the Net Hopper is easier to set up than a stereo system (I find this hard to believe, especially since the Net Hopper seems to support package filtering).

Defense Fund for Berkeley UNIX

Berry Shein, president of Software Tool & Die, is working on creating a defense fund for the University of California in the UNIX System Laboratories copyright suit against BSDI and the University of California at Berkeley.

And now to this month's questions.

 Q What is the ARPANET?

 A The ARPANET no longer exists, so the question must be rephrased as "What was the ARPANET?" However, since the ARPANET had a very significant influence on the development of the Internet as it exists today, the question is worth answering.

The ARPANET was funded by the US Department of Defense Advanced Research Projects Agency, ARPA (later DARPA) in the late 1960s. It was an experimental network that spanned the United States, and was used by the goverment to share computer resources across the continent. During the early 1980s, the TCP/IP protocol family was developed, and made generally available through the University of California at Berkeley. TCP/IP made it easier for many organizations, such as universities, to connect to the ARPANET. In just a few years, ARPANET grew from connecting relatively few machines to become the backbone of a large number of local networks. And the Internet was born. In the 1980s the ARPA network experiment was terminated by DARPA, and the NFS network, provided by the National Science Foundation took over. Today, the Internet is made up of many wide area networks, such as NFSNET, and in fact covers the entire world.

 Q You often emphasize in your writing and talks the need for system administrators to be able to deal with people. Are there any books or tutorials you can recommend to help me with this?

 A Unfortunately, I know of no books or courses that address these issues. Over the years, I've learned from practical experience and mistakes made in the process. The books I've found useful have been various books on management, even though the form of management practiced by a system administrator in dealing with users and daily management is in a somewhat different category. If I had to recommend one book, it would probably be Tom DeMarco's People Ware. This book deals mainly with software development, but it also contains good deal of common sense on how to work with people.

Changes have been slow in coming about. In the beginning, when I encouraged people to work on this area, many administrators were still completely caught up in the technical issues of the profession. Now a number of people have told me they are excited about the theme of the next LISA conference, and in just the last few weeks, an additional SAGE working group has been created. The new group, sage-managers, will explore how, from the system administrator's perspective, to manage management.

Your best bet, however, is still to use common sense, and to be able to listen to users' and management's wishes and requirements.

 Q In articles on USENET, I often see references to something called a "firewall." It seems to be something you need when you are connecting to the Internet. Could you explain a bit more?

 A A firewall is a security tool that you can use to protect your site from unwanted access from the Internet. Strictly speaking, it is not necessary, but it is very much recommended.

The firewall serves two purposes. One is to give you very high degree of control over who and what can access your site; the second is to limit this control only to the point where your site connects to the Internet. Your site is then rather like a shellfish, hard on the outside and soft on the inside.

The firewall itself consist of two items, a router and a computer, the latter often referred to as the gateway (as it is the single point of access to the Internet). The router, sometimes also called the choke, must be set up to ensure that any network packet it lets through must come from, or be destined to, the gateway machine. This makes it impossible to connect to or from any other machine on your network other than the gateway. In turn, the gateway must be set up to forward any package to or from the Internet in a reasonable manner -- otherwise, users will have to log on to the gateway machine itself, which could all too easily compromise the security of both the gateway and your system. The problems this strategy creates for e-mail can fairly easily be resolved through use of aliases and MX records. Problems with other services, like ftp, are more difficult, but can be resolved through use of a proxy mechanism, such as SOCKS (written by Michelle and David Koblas). SOCKS is available by anonymous ftp from

In the above example, the router must be configured to reject all traffic, except the one fulfilling certain requirements. It is also possible to set up a firewall with a different filtering mechanism, where traffic is let through by default and specific configurations are denied. I believe this approach to be somewhat less secure, however, and a lot more difficult to make functional.

The above explanation is somewhat simplified due to space constraint. For more information, I recommend two good books from O'Reilly and Associates, both of which can be helpful in setting up a firewall. One is the Practical UNIX Security, by Simson Garfinkel and Gene Spafford; the second is DNS and BIND, by Paul Albitz and Cricket Liu.

About the Author

Bjorn Satdeva -- email: /sys/admin, inc. The Unix System Management Experts (408) 241 3111 Send requests to the SysAdmin mailing list to