Olaf Kirch: Linux Network Administrator Guide, Second Edition

If you are not getting everything you need from posting to comp.os.linux.* groups and reading documentation, maybe it's time to consider joining SAGE, the System Administrators Guild, sponsored by USENIX. The main goal of SAGE is to advance system administration as a profession. SAGE brings together system and network administrators to foster professional and technical development, share problems and solutions, and communicate with users, management, and vendors on system administration topics.

Current SAGE initiatives include:

· Co-sponsoring the highly successful annual System Administration Conferences (LISA) with USENIX.

· Publishing Job Descriptions for System Administrators, edited by Tina Darmohray, the first in a series of very practical booklets and resource guides covering system administration issues and techniques.

· Creating an archive site, ftp.sage.usenix.org , for papers from the System Administration Conferences and sysadmin-related documentation.

· Establishing working groups in areas important to system administrators, such as jobs, publications, policies, electronic information distribution, education, vendors, and standards.

To learn more about the USENIX Association and its Special Technical Group, SAGE, contact the USENIX Association office at (510) 528-8649 in the U.S., or by email to office@usenix.org. To receive information electronically, contact info@usenix.org. Annual SAGE membership is $25 (you must also be a member of USENIX). Members enjoy free subscriptions to login: and Computing Systems, a quarterly refereed technical journal; discounts on conference and symposia registration; and savings on SAGE publication purchases and other services.

… or you are extremely impatient and know that the 24 hours it might take to download the software from the Internet is faster than the 72 hours it might take to wait for a CD-ROM to be delivered!

Terry Dawson can be reached at terry@linux.org.au.

Philip Hazel can be reached at ph10@cus.cam.ac.uk.

Note that while you are allowed to print out the online version, you may not run the O'Reilly book through a photocopier, much less sell any of its (hypothetical) copies.

The original spirit of which (see above) still shows on some occasions in Europe.

The shell is a command-line interface to the Unix operating system. It's similar to the DOS prompt in a Microsoft Windows environment, albeit much more powerful.

The Ethernet FAQ at http://www.faqs.org/faqs/LANs/ethernet-faq/ talks about this issue, and a wealth of detailed historical and technical information is available at Charles Spurgeon's Ethernet web site at http://wwwhost.ots.utexas.edu/ethernet/.

Alan can be reached at alan@lxorguk.ukuu.org.uk

NCP is the protocol on which Novell file and print services are based.

We will come back to this topic in Chapter 12, Important Network Features.

There have been commercial Unix systems (that you have to pay lots of money for) that came with a setuid-root shell script, which allowed users to gain root privilege using a simple standard trick.

In 1988, the RTM worm brought much of the Internet to a grinding halt, partly by exploiting a gaping hole in some programs including the sendmail program. This hole has long since been fixed.

The version of the Internet Protocol most frequently used on the Internet is Version 4. A lot of effort has been expended in designing a replacement called IP Version 6. IPv6 uses a different addressing scheme and larger addresses. Linux has an implementation of IPv6, but it isn't ready to document it in this book yet. The Linux kernel support for IPv6 is good, but a large number of network applications need to be modified to support it as well. Stay tuned.

Frequently, IP addresses will be assigned to you by the provider from whom you buy your IP connectivity. However, you may also apply to the NIC directly for an IP address for your network by sending email to hostmaster@internic.net, or by using the form at http://www.internic.net/.

Autonomous systems are slightly more general. They may comprise more than one IP network.

The cost of a route can be thought of, in a simple case, as the number of hops required to reach the destination. Proper calculation of route costs can be a fine art in complex network designs.

IRQs 2 and 9 are the same because the IBM PC design has two cascaded interrupt processors with eight IRQs each; the secondary processor is connected to IRQ 2 of the primary one.

People should use development kernels and report bugs if they are found; this is a very useful thing to do if you have a machine you can use as a test machine. Instructions on how to report bugs are detailed in /usr/src/linux/REPORTING-BUGS in the Linux kernel source.

Remember, the IP protocol can be carried over many different types of network, and not all network types will support packet sizes as large as Ethernet.

Paul can be reached at gpg109@rsphy1.anu.edu.au.

Fight to clear the hacking name! Always use "cracker" when you are referring to people who are consciously trying to defeat the security of a system, and "hacker" when you are referring to people who have found a clever way of solving a problem. Hackers can be crackers, but the two should never be confused. Consult the New Hackers Dictionary (popularly found as the Jargon file) for a more complete understanding of the terms.

The enhanced parallel port adaptor patch for 2.0 kernel is available from http://www.cyberelk.demon.co.uk/parport.html.

NCSA telnet is a popular program for DOS that runs TCP/IP over Ethernet or PLIP, and supports telnet and FTP.

Niibe can be reached at gniibe@mri.co.jp.

You can reach Philip at Philip.Blundell@pobox.com.

David can be reached at bf347@lafn.org.

Note that we are not talking about WinModem(TM) here! WinModems have very simple hardware and rely completely on the main CPU of your computer instead of dedicated hardware to do all of the hard work. If you're purchasing a modem, it is our strongest recommendation to not purchase such a modem; get a real modem. You may find Linux support for WinModems, but that makes them only a marginally more attractive solution.

The first number on each subnet is the subnetwork address, and the last number on each subnet is reserved as the broadcast address, so it's actually 62 hosts per subnet.

You need the address of an NIS server only if you use Peter Eriksson's NYS. Other NIS implementations locate their servers only at runtime by using ypbind.

Note that names in networks must not collide with hostnames from the hosts file, or else some programs may produce strange results.