mirror of https://github.com/tLDP/LDP
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<!doctype linuxdoc system>
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<article>
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<title> Text-Terminal-HOWTO </title>
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<title> Text-Terminal-HOWTO
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<author> David S. Lawyer <url url="mailto:dave@lafn.org">
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<date> v1.15, October 2000
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<date> v1.16, October 2000
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<!--
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Change log:
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v1.16 October 2000 Thin clients+; NC Howtos; Correction of bad typo
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"text terminals are fully obsolete". Meant to say "not fully
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obsolete". typo Unbounded => Boundless "' )
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v1.15 October 2000 Thin Clients; some broken url's changed or deleted
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v1.14 October 2000 Suse distribution uses /etc/securetty (didn't
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formerly), url of terminfo source, Serial Terminal Linux, pseudo
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@ -144,9 +147,10 @@ sites see: <url url="http://linuxdoc.org/mirrors.html">.
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Various formats are available. If you only want to quickly check the
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date of the latest version look at <url
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url="http://linuxdoc.org/HOWTO/Text-Terminal-HOWTO.html">. The
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version your are currently reading is: v1.15, October 2000 . New in this version
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is: Thin Clients; some broken url's changed or
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deleted.
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version your are currently reading is: v1.16, October 2000 . New in this version
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is: Thin-clients+; NC Howtos; Correction of bad typo "text
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terminals are fully obsolete". Meant to say "not fully obsolete".
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typo Unbounded => Boundless;
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<sect1> Related HOWTO's <label id="related_howtos">
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<p> Go to the websites shown above to get these.
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@ -154,9 +158,13 @@ deleted.
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<item> Serial-HOWTO has info on Multiport Serial Cards used for both
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terminals and banks of modems. It has general technical info on the
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serial port including troubleshooting it.
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<item> MacTerminal mini-HOWTO
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<item> Modem-HOWTO
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<item> Serial-Programming-HOWTO
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<item> NC mini-HOWTO
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<item> NCD-X-Terminal mini-HOWTO
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<item> NCD-HOWTO
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<item> Thinclient-HOWTO
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<item> Xterminal-HOWTO (unmaintained). It's at <url url=
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"http://sunsite.unc.edu/pub/Linux/docs/HOWTO/unmaintained/mini/Xterminal">
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</itemize>
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@ -257,9 +265,10 @@ server, etc.
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Other names for text terminals are "serial terminal", "character-cell
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terminal", "ASCII/ANSI terminal", "asynchronous terminal", "data
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terminal", "video terminal" and "video display terminal" (VDT). In
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olden days "video display unit" (VDU) was used for terminals but
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strictly speaking, it excludes the keyboard.
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terminal", "video terminal" and "video display terminal" (VDT) and
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"green terminal" (since many used green displays). In olden days
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"video display unit" (VDU) was used for terminals but strictly
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speaking, it excludes the keyboard.
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"Block mode" was used exclusively by old IBM mainframe terminals but
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many modern terminals also have this capability (which is not used
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@ -283,22 +292,10 @@ display images. One may form arrows <--- and draw boxes with _ and
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|. With special graphic character sets, even more is possible. By
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using all the letters, one may produce "ascii graphics" art. The term
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"graphics terminal" usually means a terminal that can display bit
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mapped images. However, this term is sometimes applied to all
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mapped images. However, this term is sometimes applied also to
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text-only terminals since text is a limited form of graphics. <label
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id="vector_graphics">
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<sect1> Thin Clients (Terminals ?)
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<p> These are either terminals or thin (minimal) computers. In
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contrast to text-terminals, they all display a high-speed GUI. They
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are dependent on higher power computers (servers) for their operation.
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For a true terminal, the computing work and disk storage will all be
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done on the server. At the other extreme, most of this work and
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storage is done at the client but some things such as administration,
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still depend on the server. Since the client here is not "thin" it's
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not clear that this is really a thin client. Some claim that
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text-terminals are also thin clients.
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<sect2> Graphics Displays
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<p> There are two basic types of graphics displays: raster and vector
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(rarely used). Raster graphics (bit-mapped) puts dots on the screen
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@ -308,74 +305,136 @@ intended to be used for monochrome screens that don't have any dots.
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They use smart electronics to draw lines and curves with an electron
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beam that can move in any direction (at any angle and location). True
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vector graphics draws high quality lines without zig-zags but is both
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rare and expensive. Raster graphics is almost universally used today.
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For PC's, images encoded in vector graphic format are sometimes used
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but they are translated to raster graphics format for display (with a
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drop in image quality).
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rare and expensive. Raster graphics is almost universally used today
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for both PCs and text terminals. For PC's, images encoded in vector
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graphic format are sometimes used but they are translated to raster
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graphics format for display (with a drop in image quality).
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<sect2> Full Graphics Terminals (often known by other names)
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<p> None of these are covered in this document. A terminal that
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deserves to be called smart is a graphics terminal which can rapidly
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display full-screen graphics just like a PC monitor. It will also
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have a mouse. Bytes sent to it often represent bit-maps for pictures
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(and other graphics). It will often use a high-speed connection to
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its host computer using twisted pair or coax cable. X-Window
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terminals are such devices. See the link to Xterminal-HOWTO at <ref
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id="related_howtos" name="Related HOWTO's">. So are some "thin
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clients" including ones which have a MS-Windows GUI which comes from a
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remote Windows Terminal Server.
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<sect1> Thin Clients (Terminals ?)
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<sect2> Introduction
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<p> These are thin (minimal) computers that behave something like
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terminals. Since text terminals (except for very old one) run an
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embedded operating system, they are also like a computer.
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Thin-clients need more computing power. In contrast to text-terminals
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thin clients all display a modern high-speed GUI. They are dependent on
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more powerful computers (servers) for their operation. For a true
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terminal, the computing work and disk storage will all be done on the
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server. At the other extreme, most of this work and storage is done
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at the client but some things such as administration, still depend on
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the server. Since such a client is not really "thin" it's a misnomer
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to call it a "thin client". Some claim that text-terminals are also
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thin clients but they are not really since they don't conform to the
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client-server model.
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Thus a thin client is like a terminal and perhaps should be called a
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terminal. The thin client has a GUI with a mouse that makes it
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seem like you are using a computer. You are, but that computer may be
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far away and have many other people using it at the same time you are.
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Communication is over a high speed network cable, often twisted pair
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(UTP). Some thin clients can in addition emulate a text terminal and
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have a serial port connector for that purpose. One even has a USB
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interface.
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There are two major types of thin clients (and some additional types as
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well which will not be discussed here). One type is the "Window
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Terminal" which usually runs under MS software and servers. The other
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type is the "network computer" which is supposed to be platform
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neutral. This implies they should work with both MS Windows and Linux
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but early models may not be easy to use with Linux.
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<sect2> Window Terminals
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<p> These can run under MS Windows NT/2000 using a proprietary protocol.
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They are true terminals since all the computing work is done by the
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server running Windows. They are also called "Window-based Terminals"
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(WBT). Some have support for unix-like systems as well and may not
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claim to be WBTs (even though they can be used as WBTs). They are
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something like computers since they run an operating system (often
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stored in flash memory so it may be updated). Some can support
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X-Windows also and can be used for Linux (from a Linux server). Many
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so called "network computers" can also run X-Windows. This will be
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discussed in the next section.
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For displaying the MS-Windows GUI, Citrix was (and is) a major player
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with what was called Winterm using it's WinFrame software (which
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supported Windows 3.1). Microsoft licensed some of this and then came
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out with Hydra (code name), also known as "Windows Terminal Server".
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It works with versions 4 or higher of MS Windows NT. Then other
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companies that had their own proprietary systems decided to support
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Microsoft's system.
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companies that had their own proprietary systems for MS Windows
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decided to support Microsoft's system.
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Citrix uses its ICA protocol and has created an add-on to Hydra known
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as pICAsso so that WinFrame (ICA) based terminals can use the Hydra
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system. There exits a Linux ICA client. Microsoft has substituted
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RDP (Remote Desktop Protocol) for ICA. Citrix has replaced WinFrame
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with MetaFrame which supports Windows 95 and is used in conjunction
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with "Windows NT Terminal Server Edition". There is also the
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"MultiConsole Personal Terminal" by Unbounded Technologies. Tektronix
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had its own multi-user interface but will now support Hydra.
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system. There exits a ICA client that internally runs Linux (but
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connects to a MS Window's server). Microsoft has substituted RDP
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(Remote Desktop Protocol) for ICA. Citrix has replaced WinFrame with
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MetaFrame which supports Windows 95, etc. and is used in conjunction
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with "Windows NT Terminal Server Edition".
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The above is sometimes called "network computing" since the terminals
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and servers connect to each other over a network. Network computers
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are something different as described below.
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may be somewhat different as described below.
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<sect2> Network Computers (NCs)
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<p>These are neither true computers nor terminals but are something
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in-between. They are also a type of thin client. One type of network
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computer (NC's) is a computer with a CPU but no hard Disk. They are
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full-graphics and connect to a server computer. They are different
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from terminals since the programs they run execute on their own CPU
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chips. Java code may be sent to them for execution. IBM calls this a
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"Network Station". They should work on IP networks and might work
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under a server running Linux. Wintel established a "NetPC" which,
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unlike the above, is almost a PC computer. However, it has no
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removable disks so users can't install their own software or obtain
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copies of anything.
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<p>These are neither true computers nor true terminals but are
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something in-between. One type of network computer (NC's) is a
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computer with a CPU but no hard Disk. The OS it needs to run is sent
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to it over a network. NCs are full-graphics and use the services of a
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server computer. They are a little different from terminals since
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some of the programs they run may execute on their own CPU chips.
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Running a browser was supposed to be one of their primary functions
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and thus Java code applets may be sent to them for execution. Many
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NCs support X-Windows so that one may use a Linux server to support
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it. IBM called their NC a "NetStation" but now calls it "NetVista".
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They should work on Intranet type networks and NetVista even runs the
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the Linux OS.
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Wintel came out with a "NetPC" which, unlike the above, is almost a PC
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computer. However, it has no removable disks so users can't install
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their own software or obtain copies of anything.
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<sect2> Thin Clients Under Linux
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<p> Linux provides NFS (Network File System) so that if ordinary
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computers (not thin clients) are connected to each other via a
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network, then a person on one computer can run programs on another
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computer. It works also with X-Windows so that one may see GUI images
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generated on another computer. Linux also allows a computer to be
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diskless (see Diskless-HOWTO) and boot over a network. Thus using a
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diskless computer which runs NFS is just like using a NC (Network
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computers are connected to each other via a network, then a person on
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one computer can run programs on another computer. Such a program
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sends messages to you over the network so that it appears just like the
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program was being run by your local computer. It works also
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with X-Windows so that one may see GUI images generated on another
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computer. Linux also allows a computer to be diskless (see
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Diskless-HOWTO) and boot over a network. Thus using a diskless
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computer which runs NFS enables you to run programs on another
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computer (the server). This is just like using a NC (Network
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Computer). It's not really a NC but it's emulating a type of NC.
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It's also sometimes referred to (incorrectly ?) as a "terminal".
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It's also often called a "terminal" and in some sense it is.
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Thus if you have an old PC with an ethernet card (NIC) you may be able
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to use it as a NC. Even if it doesn't have a NIC, you could use it as
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a text-terminal. See <ref id="term_emulation" name="Terminal
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Emulation">. So Linux too supports a type of thin client which is the
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subject of Thinclient-HOWTO. For using the Sun JavaStation NC under
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Linux see the JavaStation-HOWTO.
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to use it as a NC. The details of this are covered in
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Thinclient-HOWTO. Even if your old PC doesn't have a NIC, you could
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still use it as a text-terminal. See <ref id="term_emulation"
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name="Terminal Emulation">.
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There are also a number of genuine Network Computers (NC) that will
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work with a Linux server. Today some NCs run the Linux OS inside the
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NC. Before Linux became popular, NCs didn't run the Linux OS but
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required some other OS. But even if the NC needs a non-linux OS, it's
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often possible to make it work with a Linux Server. The non-linux OS
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is simply stored as files on the Linux Server. Then when the NC
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starts up it sends a message to the Linux Server asking for the
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non-linux OS files. This non-linux OS is thus sent to the NC over the
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network and the NC boots.
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The Linux Server runs the NFS and X-Windows both of which must be
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supported by the NC. This enables one to use the NC as if it were an
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X-Window terminal.
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There are some HOWTOs for certain brands of NCs:
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<itemize>
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<item> JavaStation-HOWTO (by Sun)
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<item> NC-HOWTO (IBM NetStation)
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<item> NCD mini-HOWTO (NCD-ThinSTAR)
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<item> NCD-X-Terminal mini-HOWTO
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</itemize>
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<sect2> Hardware hookups
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<p> There are 3 different hardware arrangements for thin clients.
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@ -548,23 +607,19 @@ and send e-mail to each other. It's similar to a local network.
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<sect1> Are Text Terminals Obsolete ?
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<p> Text terminals are technologically obsolete because for a slightly
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higher cost of hardware, one could build a smart terminal (with the
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higher cost of hardware, one could build a smarter terminal (with the
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same quality of display). This wasn't always the case since around
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1980 memory cost thousands of dollars per megabyte. Today with low
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costs for memory and processors, one could make a text terminal smart
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for only about a 10% or 20% increase in hardware cost.
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costs for memory and processors, one could turn a text terminal into a
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GUI graphic terminal for only about a 10% or 20% increase in hardware
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cost.
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The reasons that text terminals are fully obsolete are:
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The reasons that text terminals are not fully obsolete are:
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<itemize>
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<item> There is no satisfactory standard interface for smart graphics
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terminals that can be used with Linux (but there is for MS Windows).
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However one can run a diskless PC under Linux on a network where the
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diskless PC is a substitute for a smart graphics terminal.
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<item> The resolution of characters on the screen is better on
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monochrome terminals than for monitors in text mode.
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<item> Many people don't need full screen graphics.
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<item> Text terminals are low in cost and allegedly take longer to
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become obsolete, yet can give access to a much newer (and powerful)
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computer.
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<item> Since running a text-terminal (in contrast to a full-graphics
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<item> Since running a text-terminal (in contrast to a GUI-graphics
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terminal) doesn't consume much of a modern PC's resources, a large
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number of terminals may be efficiently run from one PC.
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</itemize>
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@ -3426,6 +3481,9 @@ become a serial guru. Most of the defaults should work OK and some of
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the settings are needed only for certain obsolete dumb terminals made
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in the 1970's.
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<tt/stty/ is documented in the man pages with a more detailed account
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in the info pages. Type <tt>"man stty"</tt> or <tt>"info stty"</tt>.
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Whereas <tt/setserial/ only deals with actual serial ports, stty is
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used both for serial ports and for virtual terminals such as the standard
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Linux text interface at a PC monitor. For the PC monitor, many of the
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