424 lines
12 KiB
HTML
424 lines
12 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>Background</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="The Mock Mainframe Mini-HOWTO"
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HREF="index.html"><LINK
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REL="PREVIOUS"
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TITLE="Introduction"
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HREF="x19.html"><LINK
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REL="NEXT"
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TITLE="The Individual Pieces"
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HREF="x109.html"></HEAD
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>The Mock Mainframe Mini-HOWTO</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="x19.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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></TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="x109.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="section"
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><H1
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CLASS="section"
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><A
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NAME="AEN44"
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></A
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>2. Background</H1
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><DIV
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CLASS="section"
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><H2
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CLASS="section"
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><A
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NAME="AEN46"
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></A
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>2.1. Why This Text?</H2
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><P
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> In the last decade of the past millennium, I moved out of my parents' house
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and into a small apartment with my girlfriend. I left behind not only the
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comfort of a magically refilling refrigerator, but also a computer network
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that suddenly had to survive daily and sometimes creative usage by my mom,
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dad, and kid sister for months without me. After some gentle persuasion, my
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girlfriend not only switched from Windows to Linux, but also became my
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fiancee. I left grad school and got a real job, which left me with even
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less time to fool around even with my — er, <EM
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>our</EM
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> — network, let alone my
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parents' computers. My fiancee became my wife, we left the apartment for a
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small house, and then I found myself spending more time changing diapers
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than floppies.
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</P
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><P
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> In other words, somewhere along the way, I turned into an adult.
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</P
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><P
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> It happens to the best of us, I'm told, and there are benefits that go
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beyond a <EM
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>de facto</EM
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> unlimited budget for ice cream. Having all the time in
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the world to keep computers running, however, is not one of them. I needed
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some sort of setup for the systems I am responsible for that is
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</P
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><P
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> <STRONG
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>Easy to administer.</STRONG
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> I don't have the time to do the same thing on three
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different machines, or figure out which machine needs which patch. Ideally,
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I only have to take care of one single computer in each network, and that
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infrequently. Some of the computers should not require <EM
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>any</EM
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> maintenance at
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all for months at a time.
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</P
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><P
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> <STRONG
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>Easy to afford.</STRONG
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> My hardware budget now competes with house payments, food
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bills, and the cost of clothes that my daughter seems to grow out of faster
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than we can buy them. Getting more done with less is not just an
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intellectual challenge, but a pressing necessity.
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</P
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><P
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> <STRONG
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>Easy to secure.</STRONG
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> The network's very structure should make it harder for
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outsiders to do evil things, and, more important, make it easy for me to
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create a safe "lock-down" state where threats are minimal
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until I find the time to patch holes.
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</P
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><P
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> After a few years of trial and error and a lot of time spent thinking about
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setting up computers while rocking screaming babies in the middle of the
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night, I created a "standard" setup. It is not a terribly clever or
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ingenious way of doing things, and there are probably thousands of systems
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out there organized along exactly the same lines. The aim of this text is
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to present this setup in a coherent form so that other people don't have to
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invent the wheel all over again when faced with the same problem.
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</P
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></DIV
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><DIV
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CLASS="section"
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><H2
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CLASS="section"
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><A
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NAME="AEN61"
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></A
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>2.2. Reasoning and Overview</H2
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><P
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> Most desktop computers nowadays are insanely overpowered for what they are
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doing most of the time: Email, surfing, and text processing, while maybe
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listening to music. Unless you are still using a 486DX at 66 MHz, your
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processor is probably bored out of its registers even if it is doing all of
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this at once. Check any program that shows the system load — such as
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<TT
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CLASS="literal"
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>xload</TT
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>, <TT
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CLASS="literal"
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>top</TT
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>, or <TT
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CLASS="literal"
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>uptime</TT
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> — and you'll see just how much of your
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expensive hardware is busy doing nothing.
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</P
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><P
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> With all of those resources left over, there is no technical reason why
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more than one person can't use the computer at the same time. This concept
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seems strange and downright alien to most home users today, thanks in no
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small part to Microsoft's philosophy of "a computer on every desktop" and
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the hardware companies' ad campaigns that imply that you are, among other
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things, sexually inadequate if you don't have your very own super-charged
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computer under your desk.
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</P
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><P
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> There are good commercial reasons for hard- and software companies not to
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like <EM
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>multiuser</EM
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> setups. Even if you have to upgrade the central machine,
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you are going to need less high-quality hardware than if everybody has
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their own computer; and if four people could use one Windows machine at the
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same time, that would be three copies less for Microsoft to make money on.
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You obviously don't save money if you just install Linux on one machine
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instead on four, but your hardware costs and administration time will drop.
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</P
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><P
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> Of course there are other reasons than big company ad pressure why few
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people have multiuser setups. One is computer games: Many of them suck up
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so much hardware that a multiuser-system is usually not the best idea.
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Also, until a short time ago, there was no easy way to actually have more
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than one person log on, since most desktop computers come with only one
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keyboard, one mouse, and one monitor. This has changed: You can now create
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inexpensive and reliable graphic terminals (also known as <EM
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>thin clients</EM
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>)
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with very little hassle and expense. This allows us to get away with one
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big machine and a couple of little ones. Last but not least, sharing a
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machine means you have to behave and get along with other users.
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</P
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><P
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> In a nutshell, this text is about <EM
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>centralizing small computer systems to save time and money</EM
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>. The mainframe vendor IBM wants us to believe that
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this is just what the big boys are doing, too. Now that the age of server
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mania is over, they say, companies are moving stuff back onto those
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mainframes. Since more and more of those mainframes are running roughly
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the same Linux you have at home, the only difference between a real
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mainframe and your computer is a bit of hardware. A few hundred thousand
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dollars worth of hardware at least, granted, but that doesn't mean that you
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can't use the same design principle and enjoy the benefits of a "little"
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mainframe — a "mock" mainframe, if you will.
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</P
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><P
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> The basic setup has three parts:
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</P
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><P
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> <STRONG
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>The Mock Mainframe</STRONG
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>. The one and only core machine. All users access this
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computer, either by sitting in front of it or (more likely) from a
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terminal, and they can do so at the same time. In the simplest setup, this
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machine is home to all users, holds all files, and runs all programs.
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</P
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><P
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> <STRONG
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>The Terminals.</STRONG
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> What the user actually touches. Cheap, easy to maintain,
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and expendable, they can be dual-boot machines, Linux Terminals, thin
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clients, or even X Window server programs for other operating systems.
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</P
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><P
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> <STRONG
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>Support Machines.</STRONG
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> Optional computers that perform a special task that for
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reasons of security or performance you'd rather not have on the mock
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mainframe. The most common support machine is a "guardian" that handles
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Internet connections.
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</P
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><P
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> Parts of this text will deal with installing software that is covered in
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far greater detail in other Linux HOWTOs. Caught between the extremes of
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just referring to those texts and copying everything, I have decided to
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give a very brief description of the installation procedure on a standard
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system. You'll get a general idea of what needs to be done, but for the
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details, you'll need the specialized text. This does mean that there are a
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<EM
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>lot</EM
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> of references, but that just goes to show how much
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I am standing on the shoulders of others here.
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</P
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><P
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> (Various nice people have suggested various ways of combining the basic idea with VNC. After reading their explanations and studying the documentation, I have realized that I am too out of my depth here to give sensible advice. This would be the first project for the next caretaker of this document.)
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</P
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></DIV
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><DIV
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CLASS="section"
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><H2
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CLASS="section"
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><A
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NAME="AEN84"
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></A
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>2.3. What You Should Be Aware Of</H2
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><P
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> A mock mainframe setup is not for everybody. It is based on the following
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assumptions:
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</P
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><P
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> <STRONG
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>A small group of users.</STRONG
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> Though it should scale well from a family setup
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to at least a classroom full of people (depending on the hardware and
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programs used), this is not something you want to run a university or
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Fortune-500-company with. If you are alone, it doesn't make much sense
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either. Go find somebody to move in with, then read on.
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</P
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><P
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> <STRONG
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>A sane system load.</STRONG
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> Unless you can really, really fork out a lot of money
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for serious hardware (in which case, you should probably not be looking for
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a <EM
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>mock</EM
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> mainframe), this is not a setup where you should have your kids
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playing <EM
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>Quake 3</EM
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> while you are encoding Ogg Vorbis files and your partner
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is watching a DVD, all at the same time. It is designed primarily for
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pedestrian workloads like email, browsing, chatting, and text processing.
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</P
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><P
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> <STRONG
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>Some downtime tolerance.</STRONG
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> We will be using standard, off-the-shelf,
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home-user-grade hardware. These parts are not built for enterprise strength
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work, and sooner or later, something is going to break or fail. If
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whatever you are doing urgently requires anything even close to 24/7
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uptime, you'll have to go out and buy industrial strength hardware — and
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remember to get somebody to guarantee that uptime in writing while you are
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at it.
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</P
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><P
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> Some examples of when a mock mainframe might make sense:
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</P
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><P
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></P
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><UL
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><LI
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><P
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> You have a family of email, surfing and chat freaks who all want to be
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online at the same time but don't use serious resources when they are.
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</P
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></LI
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><LI
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><P
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> You have a small, closed teaching system that can't be expensive or take
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too much time to administer.
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</P
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></LI
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><LI
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><P
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> You and your dorm buddies each have those high-powered
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computers to blow each other away with computer games, but don't want
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to go through the hassle of installing a serious Linux system on every
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one to do something as trivial as your actual course work.
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</P
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></LI
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><LI
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><P
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> Your organization has absolutely no money and the only
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hardware you can get is stuff so old, it doesn't even have scrap value
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anymore, but you still have to give your people computer access.
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</P
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></LI
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></UL
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><P
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> (If you have found other situations where this setup works, please let me
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know.)
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</P
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></DIV
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><DIV
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CLASS="section"
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><H2
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CLASS="section"
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><A
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NAME="AEN106"
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></A
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>2.4. How This Text Is Organized</H2
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><P
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> First, we will take a look at the individual parts of the setup — the mock
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mainframe, the terminals, the support computers. Then we'll discuss ways
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of putting these elements together. This is also where we will talk about
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security. We'll also discuss life with more than one user and setups for
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very weak hardware.
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</P
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></DIV
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></DIV
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CLASS="NAVFOOTER"
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="x19.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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VALIGN="top"
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HREF="x109.html"
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ACCESSKEY="N"
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>Next</A
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Introduction</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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> </TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>The Individual Pieces</TD
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> |