83 lines
3.7 KiB
HTML
83 lines
3.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>Layout of UUCP Transfers and Remote Execution</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node151.html">The Inner Workings of </A>
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<B>Up:</B> <A HREF="node149.html">Introduction</A>
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<B> Previous:</B> <A HREF="node149.html">Introduction</A>
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<BR> <P>
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<H2><A NAME="SECTION0014210000">Layout of UUCP Transfers and Remote Execution</A></H2>
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<P>
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<A NAME="uucpintrogrades"></A>
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<P>
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<A NAME="5642"></A>
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Vital to the understanding of UUCP is the concept of <em>jobs</em>.
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Every transfer a user initiates with uucp or uux is
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called a job. It is made up of a <em>command</em> to be executed on
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a remote system, and a collection of <em>files</em> to be transferred
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between sites. One of these parts may be missing.
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<P>
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As an example, assume you issued the following command on your host, which
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makes UUCP copy the file netguide.ps to host pablo, and
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makes it execute the lpr command to print the file.
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<P>
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<P><P>
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<P>
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<A NAME="5653"></A>
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UUCP does not generally call the remote system immediately to execute
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a job (else you could make do with kermit). Instead, it
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temporarily stores the job description away. This is called
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<em>spooling</em>. The directory tree under which jobs are stored is
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therefore called the <em>spool directory</em> and is generally located
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in /var/spool/uucp. In our example, the job description would contain
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information about the remote command to be executed (lpr), the
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user who requested the execution, and a couple of other items. In
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addition to the job description, UUCP has to store the input file,
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netguide.ps.
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<P>
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The exact location and naming of spool files may vary, depending on
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some compile-time options. HDB-compatible UUCP's generally store spool
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files in a directory named /var/spool/uucp/site, where
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site is the name of the remote site. When compiled for Taylor
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configuration, UUCP will create subdirectories below the site-specific
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spool directory for different types of spool files.
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<P>
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At regular intervals, UUCP dials up the remote system. When a
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connection to the remote machine is established, UUCP transfers the
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files describing the job, plus any input files. The incoming jobs
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will not be executed immediately, but only after the connection
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terminates. This is done by uuxqt, which also takes care of
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forwarding any jobs if they are designated for another site.
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<P>
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<A NAME="5662"></A>
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<A NAME="5663"></A>
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<A NAME="5664"></A>
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To distinguish between important and less important jobs, UUCP
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associates a <em>grade</em> with each job. This is a single letter,
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ranging from 0 through 9, A though Z, and a through z, in decreasing
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precedence. Mail is customarily spooled with grade B or C, while news
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is spooled with grade N. Jobs with higher grade are transferred
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earlier. Grades may be assigned using the -g flag when
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invoking uucp or uux.
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<P>
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You can also disallow the transfer of jobs below a given grade at
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certain times. This is also called the <em>maximum spool grade</em>
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allowed during a conversation and defaults to-z. Note the
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terminological ambiguity here: a file is transferred only if it is
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<em>equal or above</em> the maximum spool grade.
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<P>
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node151.html">The Inner Workings of </A>
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<B>Up:</B> <A HREF="node149.html">Introduction</A>
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<B> Previous:</B> <A HREF="node149.html">Introduction</A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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