mirror of https://github.com/tLDP/LDP
836 lines
36 KiB
XML
836 lines
36 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1" ?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<article id="Secure-CVS-Pserver">
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<articleinfo>
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<title>Secure CVS Pserver Mini-HOWTO</title>
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<author>
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<firstname>Morgon</firstname>
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<surname>Kanter</surname>
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<affiliation>
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<address>
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<email>morgon AT surgo DOT net</email>
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</address>
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</affiliation>
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</author>
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<copyright>
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<year>2003</year>
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<holder>Morgon Kanter</holder>
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</copyright>
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<legalnotice>
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<para>
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Permission is granted to copy, distribute, and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.2
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
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A copy of the license is included in <xref linkend="gfdl" />, entitled "GNU
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Free Documentation License".
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</para>
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</legalnotice>
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<pubdate>February 2003</pubdate>
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<revhistory id="revhistory">
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<revision>
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<revnumber>1.1</revnumber>
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<date>2003-03-21</date>
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<authorinitials>mk</authorinitials>
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<revremark>Fixed a missing link and added a section on CVSGrab</revremark>
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</revision>
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<revision>
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<revnumber>1.0</revnumber>
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<date>2003-02-01</date>
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<authorinitials>mk</authorinitials>
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<revremark>Initial Release, reviewed by LDP.</revremark>
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</revision>
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</revhistory>
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<abstract><para>
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This document will help you set up a more secure CVS
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Pserver for anonymous CVS access.
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</para></abstract>
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</articleinfo>
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<sect1 id="intro">
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<title>Introduction</title>
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<para>
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CVS Pserver is, by definition, an insecure protocol. Among
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other things, passwords are transmitted in plain text, making it
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undesirable for much use. However, CVS Pserver is very good for
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providing anonymous CVS access to a repository.
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</para>
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<para>
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In this document we will introduce you to setting up a CVS
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repository (although not intruding on the CVS HOWTO's space),
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and how to set up a chroot jail for the Pserver.
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We will also talk about using SSH for developer access to a repository.
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</para>
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</sect1>
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<sect1 id="gettools">
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<title>Getting the tools</title>
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<sect2>
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<title>What you need</title>
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<para>
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You'll need the following things in order to set up a secure Pserver:
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</para>
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<variablelist>
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<varlistentry>
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<term>CVS</term>
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<listitem><para>
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Of course, you will need to have CVS in order to be running it.
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You can get it <ulink url="http://www.cvshome.org">here</ulink>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>cvsd</term>
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<listitem><para>
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<command>cvsd</command> is a program that will run the CVS Pserver
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in a chroot jail. You can get it <ulink url="http://tiefighter.et.tudelft.nl/~arthur/cvsd/">here</ulink>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>SSHd</term>
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<listitem><para>
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If you want your developers to have secure access to the repository,
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you'll have to be running an SSH server. However, setting up that
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access is beyond the scope of this Mini-HOWTO. More information can be found at
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<ulink url="http://www.tldp.org/HOWTO/CVS-RCS-HOWTO.html">the CVS-RCS howto</ulink>.
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</para></listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2 id="compiletools">
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<title>Compiling the tools</title>
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<para>
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If you are compiling from the sources, follow these instructions.
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If you downloaded binaries, skip ahead to <xref linkend="compilecvsd" />.
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</para>
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<sect3 id="compilecvs">
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<title>Compiling CVS</title>
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<para>
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After you have downloaded the CVS sources, unpack them into a
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directory and <command>cd</command> into it. The default prefix is
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<filename class="directory">/usr/local</filename>; we've changed it
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to <filename class="directory">/usr</filename> for this example.
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You might want to change <varname>mandir</varname> to wherever
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your man pages reside (the default is
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<filename class="directory">PREFIX/man</filename>).
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</para>
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<informalexample><programlisting>
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<prompt>$</prompt> ./configure --prefix=/usr
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<prompt>$</prompt> make
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<prompt>#</prompt> make install
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</programlisting></informalexample>
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</sect3>
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<sect3 id="compilecvsd">
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<title>Compiling cvsd</title>
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<para>
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There are a few configure switches you should be aware of here.
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The default prefix is <filename class="directory">/usr/local</filename>,
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which in this document we are changing to <filename class="directory">/usr</filename>.
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You should also change <varname>sysconfdir</varname> to
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<filename class="directory">/etc</filename>, where the system
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config files usually reside. You might want to change
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<varname>mandir</varname> to wherever your manual pages reside as
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well.
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</para>
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<informalexample><programlisting>
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<prompt>$</prompt> ./configure --prefix=/usr --sysconfdir=/etc
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<prompt>$</prompt> make
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<prompt>#</prompt> make install
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</programlisting></informalexample>
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<para>
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Now lets go on to setting up these wonderful tools.
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</para>
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</sect3>
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</sect2>
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</sect1>
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<sect1 id="setuptools">
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<title>Setting up the tools</title>
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<para>
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Now that CVS and cvsd are built, let's set them up.
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</para>
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<sect2 id="createrepository">
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<title>Creating the CVS Repository</title>
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<para>
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Before we begin, I strongly recommend you read the CVS manual that
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was installed with the rest of CVS. If the stand-alone info browser
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or the texinfo package is installed on your system, you can see
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this manual by typing the command <command>info cvs</command> at your shell.
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</para>
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<para>
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First, plan out where you want your repository. Debian defaults to
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<filename class="directory">/var/lib/cvs</filename>. My repository
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is under the directory <filename class="directory">/cvs/root</filename>,
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and is on its own small partition. What you do depends on your needs
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and can vary widely.
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<important>
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<para>
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Make sure that the repository is a subdirectory of an empty directory! For example, if you are installing it into <filename class="directory">/var/lib/cvs</filename>, put the repository in <filename class="directory">/var/lib/cvs/root</filename> (or whatever you want for the last directory). This is because we create a chroot jail for the Pserver!
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</para>
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</important>
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</para>
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<para>
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After you have planned where you want to put your repository,
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made the necessary partitions, if desired, and run the following command
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(we assume that it will be at <filename class="directory">/cvs/root</filename>):
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</para>
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<informalexample><programlisting>
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<prompt>$</prompt> cvs -d /cvs/root init
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</programlisting></informalexample>
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<para>
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That will initialize your repository and set up the necessary
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<envar>CVSROOT</envar> files.
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</para>
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</sect2>
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<sect2 id="setupjail">
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<title>Setting up the jail</title>
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<para>
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Now that we have the <envar>CVSROOT</envar> set up, we need to copy the
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appropriate libraries and files for cvsd, which runs the
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Pserver in the chroot jail.
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</para>
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<sect3 id="copyfiles">
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<title>Transferring the necessary files</title>
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<para>
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<note>
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<para>If you installed cvsd from a package management system like
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RPM, this may already be done for you. If that is the case,
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skip ahead to the next step.</para>
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</note>
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Change your directory to <filename class="directory">/cvs</filename> (or whatever the directory before your root is) and enter the following commands:
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</para>
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<informalexample><programlisting>
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<prompt>$</prompt> cvsd-buildroot /cvs
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<prompt>$</prompt> mkdir -p var/lock
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<prompt>$</prompt> adduser cvsd
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<prompt>$</prompt> addgroup cvsd
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</programlisting></informalexample>
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<para>
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Thankfully, cvsd comes with the script <command>cvsd-buildroot</command>, so we don't have to do all the necessary copying by hand. However, you should edit the <filename>/cvs/etc/passwd</filename> file, and remove the entry for <quote>root,</quote> as it's unneeded.
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</para>
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</sect3>
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<sect3 id="configcvsd">
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<title>Configuring cvsd</title>
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<para>
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The defaults in <filename>/etc/cvsd/cvsd.conf</filename> are okay, but can be less than desirable. Make sure that <envar>RootJail</envar> is set to wherever the chroot jail you built is, and the repository is the directory where the repository is <emphasis role="bold">relative to the chroot jail</emphasis>. Set <varname>maxconnections</varname> to whatever you desire, and make sure that Uid and Gid are set to cvsd. If you are lacking an already-built <filename>cvsd.conf</filename> file, here is mine:
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</para>
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<example>
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<title>My <filename>cvsd.conf</filename></title>
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<programlisting>
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Uid cvsd
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Gid cvsd
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PidFile /var/run/cvsd.pid
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RootJail /cvs
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MaxConnections 10
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Nice 1
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Listen * 2401
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Repos /root
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Limit coredumpsize 0
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</programlisting>
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</example>
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</sect3>
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</sect2>
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<sect2 id="addanonaccess">
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<title>Adding anonymous access</title>
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<para>
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It's back to configuring CVS, but don't worry, we are almost
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there! We have to edit a couple of necessary files to allow for
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anonymous access. First, making sure you aren't in the CVS directory,
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check out the CVSROOT module:
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</para>
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<informalexample><programlisting>
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<prompt>#</prompt> cvs -d /cvs/root checkout CVSROOT
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<prompt>#</prompt> cd CVSROOT
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</programlisting></informalexample>
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<para>
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Now edit the file <filename>READERS</filename>. Create it if it isn't there, and add a line that reads <quote>anonymous</quote>.
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<important>
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<para>You NEED to have an extra line at the end of the file!</para>
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</important>
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The file <filename>READERS</filename> is a list of users who have
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read-only access to the CVS repository. People with write access
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are listed in the file <filename>WRITERS</filename>. Read the cvs
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manual <footnote id="ftn-try-info-cvs"><para>info cvs, if you have the stand-alone
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<command>info</command> viewer installed on your system</para></footnote>
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for more information on these files.
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</para>
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<para>
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Now commit the repository with the command below. We assume
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that your current working directory is <envar>CVSROOT</envar>. If it
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isn't, forget the <command>cd</command> step.
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</para>
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<informalexample><programlisting>
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<prompt>#</prompt> cd ../
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<prompt>#</prompt> cvs -d /cvs/root commit
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</programlisting></informalexample>
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<para>
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You should now get a message that says something like <computeroutput>Re-building administrative files</computeroutput>, which means that it was successful.
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</para>
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<para>
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One last step and we're all done! Run the following command,
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and when prompted for a password, just press <keycap>ENTER</keycap>:
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</para>
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<informalexample><programlisting>
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<prompt>#</prompt> cvsd-passwd /cvs/root anonymous
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</programlisting></informalexample>
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<para>
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Congratulations! You now have secure, anonymous CVS Pserver access
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to the repository!
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</para>
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</sect2>
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<sect2 id="lockfilelocation">
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<title>Not quite done yet! Changing lock file locations</title>
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<para>
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There is one small feature here that is really beyond the scope
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of this Mini-HOWTO but is worth noting nonetheless. It is the
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ability to change the directory where the Pserver will place lock files.
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</para>
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<para>
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Normally the Pserver will place lock files in the same directory
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as the files that you are trying to check out, but this can cause
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permissions mayhem. Step back to when we built the chroot
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jail for cvsd; we also created the directory <filename class="directory">var/lock</filename>. This is where we will place the lockfiles instead.
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</para>
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<para>
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So use the following example, replacing <filename class="directory">/cvs</filename> with wherever your <envar>chroot</envar> environment is, and <filename class="directory">var</filename> with wherever the locks are going to be placed. Mine are placed in <filename class="directory">var/lock</filename>, and there is nothing else under <filename class="directory">var</filename>, so a <command>chown -R</command> is safe. Also, replace the cvsd user and group ids with the user and group ids that cvsd runs as.
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</para>
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<informalexample><programlisting>
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<prompt>#</prompt> cd /cvs
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<prompt>#</prompt> chown -R cvsd:cvsd var
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<prompt>#</prompt> chmod -R 775 var
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<prompt>#</prompt> cd
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<prompt>#</prompt> cvs -d /cvs/root checkout CVSROOT
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<prompt>#</prompt> cd CVSROOT
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</programlisting></informalexample>
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<para>
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Now we want to edit the file <filename>config</filename>. Change
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lock dir to the directory you want the locks to be placed, in our
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case <filename class="directory">/var/lock</filename>.
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<important>
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<para>Note that this applies to the Pserver <emphasis role="bold">
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AS WELL AS THE NON-CHROOT SSH LOGIN METHOD!</emphasis>
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Ensure that this directory is not only in existence, but that you can
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write to it as well, relative to your root directory. This is why I have
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chosen <filename class="directory">/var/lock</filename>, because it satisfies those conditions.</para>
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</important>
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Now commit the changes:
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</para>
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<informalexample><programlisting>
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<prompt>#</prompt> cd ../
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<prompt>#</prompt> cvs -d /cvs/root commit
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</programlisting></informalexample>
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<para>
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And that's it!
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</para>
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</sect2>
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</sect1>
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<sect1 id="pserveralternatives">
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<title>Alternatives to the Pserver</title>
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<sect2 id="developeraccess">
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<title>Access for developers</title>
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<para>
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Pserver is not a very good method to implement for your fellow developers
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to access the repository. You can use CVS's SSH and ext method.
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Simply add the user to the server's list of users, add the user
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to the file WRITERS, and then they can do the following:
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</para>
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<informalexample><programlisting>
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<prompt>$</prompt> export CVS_RSH='/usr/bin/ssh'
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<prompt>$</prompt> cvs -d :ext:username@server.hostname:/cvs/root login
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</programlisting></informalexample>
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<para>
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This is a much more secure way for developers to access the
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repository.
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</para>
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</sect2>
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<sect2 id="anonhttpaccess">
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<title>Anonymous CVS access by http</title>
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<para>
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There is another way to allow anonymous access to CVS. If there
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is an http server and Python installed on the server, you can use
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a set of Python CGI scripts called <ulink url="http://viewcvs.sourceforge.net">
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viewcvs</ulink>, which allow people to view the CVS repository over
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the web, and can generate tarballs for users to download.
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</para>
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<para>
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There is also a set of Perl CGI scripts that do the same thing
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called <ulink url="http://stud.fh-heilbronn.de/~zeller/cgi/cvsweb.cgi/">
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cvsweb</ulink>, but Viewcvs is more mature and is preferred (at
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least by me).
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</para>
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</sect2>
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<sect2 id="cvsgrab">
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<title>CVSGrab</title>
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<para>
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<ulink url="http://cvsgrab.sourceforge.net">CVSGrab</ulink> is an
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end-user tool for downloading the CVS repository by a ViewCVS
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interface. It is very useful when you are behind a corporate
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firewall that blocks the Pserver, as you can just grab the repository
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over standard HTTP. The only problem is if it doesn't have a
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ViewCVS interface, but most free software
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repositories are now on the web, and the few that still use
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cvsweb seem to be switching over to ViewCVS.
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</para><para>
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CVSGrab is written in Java, which may at first be a turn-off to
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some people (it is to me), but it seems completely compilable
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using <application>GCJ</application>, the Java front-end to GCC.
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</para><para>
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CVSGrab is a tool that goes hand-in-hand with
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ViewCVS. It is an end-user tool, not one that you as a system
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administrator or repository administrator would set up and configure.
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</para>
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</sect2>
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</sect1>
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|
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<sect1 id="acknowledgements">
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|
<title>Acknowledgements</title>
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|
<para>
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|
This Mini-HOWTO was written by Morgon Kanter, who is reachable
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at <email>morgon AT surgo DOT net</email>, public key available from
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<ulink url="http://www.surgo.net/pubkey.asc">http://www.surgo.net/pubkey.asc</ulink>.
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|
Email all problems with this document to him, and they will be fixed
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|
ASAP.
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|
</para><para>
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|
My thanks goes out to all the people who contributed to CVS over the
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|
years, as well as the creators of Viewcvs, and in turn the creators
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of cvsweb who inspired it.
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</para><para>
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I would also like to thank Tabatha Persad for reviewing and helping me edit
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this monster, as well as putting up with me. Thanks!
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</para><para>
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|
Also thanks to the various email contributors who pointed out missing
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stuff. Thank you Y Giridhar Appaji Nag and Pasi Hirvonen!
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</para>
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|
</sect1>
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|
|
<sect1 id="gfdl">
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|
<title>GNU Free Documentation License</title>
|
|
<screen>
|
|
GNU Free Documentation License
|
|
Version 1.2, November 2002
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|
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Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
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59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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Everyone is permitted to copy and distribute verbatim copies
|
|
of this license document, but changing it is not allowed.
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0. PREAMBLE
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|
|
The purpose of this License is to make a manual, textbook, or other
|
|
functional and useful document "free" in the sense of freedom: to
|
|
assure everyone the effective freedom to copy and redistribute it,
|
|
with or without modifying it, either commercially or noncommercially.
|
|
Secondarily, this License preserves for the author and publisher a way
|
|
to get credit for their work, while not being considered responsible
|
|
for modifications made by others.
|
|
|
|
This License is a kind of "copyleft", which means that derivative
|
|
works of the document must themselves be free in the same sense. It
|
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complements the GNU General Public License, which is a copyleft
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license designed for free software.
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We have designed this License in order to use it for manuals for free
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software, because free software needs free documentation: a free
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program should come with manuals providing the same freedoms that the
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software does. But this License is not limited to software manuals;
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it can be used for any textual work, regardless of subject matter or
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whether it is published as a printed book. We recommend this License
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principally for works whose purpose is instruction or reference.
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1. APPLICABILITY AND DEFINITIONS
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This License applies to any manual or other work, in any medium, that
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contains a notice placed by the copyright holder saying it can be
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distributed under the terms of this License. Such a notice grants a
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world-wide, royalty-free license, unlimited in duration, to use that
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work under the conditions stated herein. The "Document", below,
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refers to any such manual or work. Any member of the public is a
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licensee, and is addressed as "you". You accept the license if you
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copy, modify or distribute the work in a way requiring permission
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under copyright law.
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A "Modified Version" of the Document means any work containing the
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Document or a portion of it, either copied verbatim, or with
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modifications and/or translated into another language.
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A "Secondary Section" is a named appendix or a front-matter section of
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the Document that deals exclusively with the relationship of the
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publishers or authors of the Document to the Document's overall subject
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(or to related matters) and contains nothing that could fall directly
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within that overall subject. (Thus, if the Document is in part a
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textbook of mathematics, a Secondary Section may not explain any
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mathematics.) The relationship could be a matter of historical
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connection with the subject or with related matters, or of legal,
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commercial, philosophical, ethical or political position regarding
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them.
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The "Invariant Sections" are certain Secondary Sections whose titles
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are designated, as being those of Invariant Sections, in the notice
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that says that the Document is released under this License. If a
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section does not fit the above definition of Secondary then it is not
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allowed to be designated as Invariant. The Document may contain zero
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Invariant Sections. If the Document does not identify any Invariant
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Sections then there are none.
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The "Cover Texts" are certain short passages of text that are listed,
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as Front-Cover Texts or Back-Cover Texts, in the notice that says that
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the Document is released under this License. A Front-Cover Text may
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be at most 5 words, and a Back-Cover Text may be at most 25 words.
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A "Transparent" copy of the Document means a machine-readable copy,
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represented in a format whose specification is available to the
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general public, that is suitable for revising the document
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straightforwardly with generic text editors or (for images composed of
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pixels) generic paint programs or (for drawings) some widely available
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drawing editor, and that is suitable for input to text formatters or
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for automatic translation to a variety of formats suitable for input
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to text formatters. A copy made in an otherwise Transparent file
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format whose markup, or absence of markup, has been arranged to thwart
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or discourage subsequent modification by readers is not Transparent.
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An image format is not Transparent if used for any substantial amount
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of text. A copy that is not "Transparent" is called "Opaque".
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Examples of suitable formats for Transparent copies include plain
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ASCII without markup, Texinfo input format, LaTeX input format, SGML
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or XML using a publicly available DTD, and standard-conforming simple
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HTML, PostScript or PDF designed for human modification. Examples of
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transparent image formats include PNG, XCF and JPG. Opaque formats
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include proprietary formats that can be read and edited only by
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proprietary word processors, SGML or XML for which the DTD and/or
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processing tools are not generally available, and the
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machine-generated HTML, PostScript or PDF produced by some word
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processors for output purposes only.
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The "Title Page" means, for a printed book, the title page itself,
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plus such following pages as are needed to hold, legibly, the material
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this License requires to appear in the title page. For works in
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formats which do not have any title page as such, "Title Page" means
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the text near the most prominent appearance of the work's title,
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preceding the beginning of the body of the text.
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A section "Entitled XYZ" means a named subunit of the Document whose
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title either is precisely XYZ or contains XYZ in parentheses following
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text that translates XYZ in another language. (Here XYZ stands for a
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specific section name mentioned below, such as "Acknowledgements",
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"Dedications", "Endorsements", or "History".) To "Preserve the Title"
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of such a section when you modify the Document means that it remains a
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section "Entitled XYZ" according to this definition.
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The Document may include Warranty Disclaimers next to the notice which
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states that this License applies to the Document. These Warranty
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Disclaimers are considered to be included by reference in this
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License, but only as regards disclaiming warranties: any other
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implication that these Warranty Disclaimers may have is void and has
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no effect on the meaning of this License.
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2. VERBATIM COPYING
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You may copy and distribute the Document in any medium, either
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commercially or noncommercially, provided that this License, the
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copyright notices, and the license notice saying this License applies
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to the Document are reproduced in all copies, and that you add no other
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conditions whatsoever to those of this License. You may not use
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technical measures to obstruct or control the reading or further
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copying of the copies you make or distribute. However, you may accept
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compensation in exchange for copies. If you distribute a large enough
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number of copies you must also follow the conditions in section 3.
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You may also lend copies, under the same conditions stated above, and
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you may publicly display copies.
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3. COPYING IN QUANTITY
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If you publish printed copies (or copies in media that commonly have
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printed covers) of the Document, numbering more than 100, and the
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Document's license notice requires Cover Texts, you must enclose the
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copies in covers that carry, clearly and legibly, all these Cover
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Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
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the back cover. Both covers must also clearly and legibly identify
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you as the publisher of these copies. The front cover must present
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the full title with all words of the title equally prominent and
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visible. You may add other material on the covers in addition.
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Copying with changes limited to the covers, as long as they preserve
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the title of the Document and satisfy these conditions, can be treated
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as verbatim copying in other respects.
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If the required texts for either cover are too voluminous to fit
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legibly, you should put the first ones listed (as many as fit
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reasonably) on the actual cover, and continue the rest onto adjacent
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pages.
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If you publish or distribute Opaque copies of the Document numbering
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more than 100, you must either include a machine-readable Transparent
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copy along with each Opaque copy, or state in or with each Opaque copy
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a computer-network location from which the general network-using
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public has access to download using public-standard network protocols
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a complete Transparent copy of the Document, free of added material.
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If you use the latter option, you must take reasonably prudent steps,
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when you begin distribution of Opaque copies in quantity, to ensure
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that this Transparent copy will remain thus accessible at the stated
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location until at least one year after the last time you distribute an
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Opaque copy (directly or through your agents or retailers) of that
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edition to the public.
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It is requested, but not required, that you contact the authors of the
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Document well before redistributing any large number of copies, to give
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them a chance to provide you with an updated version of the Document.
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4. MODIFICATIONS
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You may copy and distribute a Modified Version of the Document under
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the conditions of sections 2 and 3 above, provided that you release
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the Modified Version under precisely this License, with the Modified
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Version filling the role of the Document, thus licensing distribution
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and modification of the Modified Version to whoever possesses a copy
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of it. In addition, you must do these things in the Modified Version:
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A. Use in the Title Page (and on the covers, if any) a title distinct
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from that of the Document, and from those of previous versions
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(which should, if there were any, be listed in the History section
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|
of the Document). You may use the same title as a previous version
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if the original publisher of that version gives permission.
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|
B. List on the Title Page, as authors, one or more persons or entities
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responsible for authorship of the modifications in the Modified
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Version, together with at least five of the principal authors of the
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Document (all of its principal authors, if it has fewer than five),
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unless they release you from this requirement.
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C. State on the Title page the name of the publisher of the
|
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Modified Version, as the publisher.
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D. Preserve all the copyright notices of the Document.
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E. Add an appropriate copyright notice for your modifications
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|
adjacent to the other copyright notices.
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F. Include, immediately after the copyright notices, a license notice
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giving the public permission to use the Modified Version under the
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terms of this License, in the form shown in the Addendum below.
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G. Preserve in that license notice the full lists of Invariant Sections
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and required Cover Texts given in the Document's license notice.
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H. Include an unaltered copy of this License.
|
|
I. Preserve the section Entitled "History", Preserve its Title, and add
|
|
to it an item stating at least the title, year, new authors, and
|
|
publisher of the Modified Version as given on the Title Page. If
|
|
there is no section Entitled "History" in the Document, create one
|
|
stating the title, year, authors, and publisher of the Document as
|
|
given on its Title Page, then add an item describing the Modified
|
|
Version as stated in the previous sentence.
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|
J. Preserve the network location, if any, given in the Document for
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|
public access to a Transparent copy of the Document, and likewise
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the network locations given in the Document for previous versions
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|
it was based on. These may be placed in the "History" section.
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|
You may omit a network location for a work that was published at
|
|
least four years before the Document itself, or if the original
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|
publisher of the version it refers to gives permission.
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K. For any section Entitled "Acknowledgements" or "Dedications",
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Preserve the Title of the section, and preserve in the section all
|
|
the substance and tone of each of the contributor acknowledgements
|
|
and/or dedications given therein.
|
|
L. Preserve all the Invariant Sections of the Document,
|
|
unaltered in their text and in their titles. Section numbers
|
|
or the equivalent are not considered part of the section titles.
|
|
M. Delete any section Entitled "Endorsements". Such a section
|
|
may not be included in the Modified Version.
|
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N. Do not retitle any existing section to be Entitled "Endorsements"
|
|
or to conflict in title with any Invariant Section.
|
|
O. Preserve any Warranty Disclaimers.
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|
|
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If the Modified Version includes new front-matter sections or
|
|
appendices that qualify as Secondary Sections and contain no material
|
|
copied from the Document, you may at your option designate some or all
|
|
of these sections as invariant. To do this, add their titles to the
|
|
list of Invariant Sections in the Modified Version's license notice.
|
|
These titles must be distinct from any other section titles.
|
|
|
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You may add a section Entitled "Endorsements", provided it contains
|
|
nothing but endorsements of your Modified Version by various
|
|
parties--for example, statements of peer review or that the text has
|
|
been approved by an organization as the authoritative definition of a
|
|
standard.
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|
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You may add a passage of up to five words as a Front-Cover Text, and a
|
|
passage of up to 25 words as a Back-Cover Text, to the end of the list
|
|
of Cover Texts in the Modified Version. Only one passage of
|
|
Front-Cover Text and one of Back-Cover Text may be added by (or
|
|
through arrangements made by) any one entity. If the Document already
|
|
includes a cover text for the same cover, previously added by you or
|
|
by arrangement made by the same entity you are acting on behalf of,
|
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you may not add another; but you may replace the old one, on explicit
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permission from the previous publisher that added the old one.
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The author(s) and publisher(s) of the Document do not by this License
|
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give permission to use their names for publicity for or to assert or
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|
imply endorsement of any Modified Version.
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5. COMBINING DOCUMENTS
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|
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You may combine the Document with other documents released under this
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License, under the terms defined in section 4 above for modified
|
|
versions, provided that you include in the combination all of the
|
|
Invariant Sections of all of the original documents, unmodified, and
|
|
list them all as Invariant Sections of your combined work in its
|
|
license notice, and that you preserve all their Warranty Disclaimers.
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The combined work need only contain one copy of this License, and
|
|
multiple identical Invariant Sections may be replaced with a single
|
|
copy. If there are multiple Invariant Sections with the same name but
|
|
different contents, make the title of each such section unique by
|
|
adding at the end of it, in parentheses, the name of the original
|
|
author or publisher of that section if known, or else a unique number.
|
|
Make the same adjustment to the section titles in the list of
|
|
Invariant Sections in the license notice of the combined work.
|
|
|
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In the combination, you must combine any sections Entitled "History"
|
|
in the various original documents, forming one section Entitled
|
|
"History"; likewise combine any sections Entitled "Acknowledgements",
|
|
and any sections Entitled "Dedications". You must delete all sections
|
|
Entitled "Endorsements".
|
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|
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6. COLLECTIONS OF DOCUMENTS
|
|
|
|
You may make a collection consisting of the Document and other documents
|
|
released under this License, and replace the individual copies of this
|
|
License in the various documents with a single copy that is included in
|
|
the collection, provided that you follow the rules of this License for
|
|
verbatim copying of each of the documents in all other respects.
|
|
|
|
You may extract a single document from such a collection, and distribute
|
|
it individually under this License, provided you insert a copy of this
|
|
License into the extracted document, and follow this License in all
|
|
other respects regarding verbatim copying of that document.
|
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|
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7. AGGREGATION WITH INDEPENDENT WORKS
|
|
|
|
A compilation of the Document or its derivatives with other separate
|
|
and independent documents or works, in or on a volume of a storage or
|
|
distribution medium, is called an "aggregate" if the copyright
|
|
resulting from the compilation is not used to limit the legal rights
|
|
of the compilation's users beyond what the individual works permit.
|
|
When the Document is included an aggregate, this License does not
|
|
apply to the other works in the aggregate which are not themselves
|
|
derivative works of the Document.
|
|
|
|
If the Cover Text requirement of section 3 is applicable to these
|
|
copies of the Document, then if the Document is less than one half of
|
|
the entire aggregate, the Document's Cover Texts may be placed on
|
|
covers that bracket the Document within the aggregate, or the
|
|
electronic equivalent of covers if the Document is in electronic form.
|
|
Otherwise they must appear on printed covers that bracket the whole
|
|
aggregate.
|
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8. TRANSLATION
|
|
|
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Translation is considered a kind of modification, so you may
|
|
distribute translations of the Document under the terms of section 4.
|
|
Replacing Invariant Sections with translations requires special
|
|
permission from their copyright holders, but you may include
|
|
translations of some or all Invariant Sections in addition to the
|
|
original versions of these Invariant Sections. You may include a
|
|
translation of this License, and all the license notices in the
|
|
Document, and any Warrany Disclaimers, provided that you also include
|
|
the original English version of this License and the original versions
|
|
of those notices and disclaimers. In case of a disagreement between
|
|
the translation and the original version of this License or a notice
|
|
or disclaimer, the original version will prevail.
|
|
|
|
If a section in the Document is Entitled "Acknowledgements",
|
|
"Dedications", or "History", the requirement (section 4) to Preserve
|
|
its Title (section 1) will typically require changing the actual
|
|
title.
|
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9. TERMINATION
|
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|
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You may not copy, modify, sublicense, or distribute the Document except
|
|
as expressly provided for under this License. Any other attempt to
|
|
copy, modify, sublicense or distribute the Document is void, and will
|
|
automatically terminate your rights under this License. However,
|
|
parties who have received copies, or rights, from you under this
|
|
License will not have their licenses terminated so long as such
|
|
parties remain in full compliance.
|
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|
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10. FUTURE REVISIONS OF THIS LICENSE
|
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|
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The Free Software Foundation may publish new, revised versions
|
|
of the GNU Free Documentation License from time to time. Such new
|
|
versions will be similar in spirit to the present version, but may
|
|
differ in detail to address new problems or concerns. See
|
|
http://www.gnu.org/copyleft/.
|
|
|
|
Each version of the License is given a distinguishing version number.
|
|
If the Document specifies that a particular numbered version of this
|
|
License "or any later version" applies to it, you have the option of
|
|
following the terms and conditions either of that specified version or
|
|
of any later version that has been published (not as a draft) by the
|
|
Free Software Foundation. If the Document does not specify a version
|
|
number of this License, you may choose any version ever published (not
|
|
as a draft) by the Free Software Foundation.
|
|
|
|
|
|
ADDENDUM: How to use this License for your documents
|
|
|
|
To use this License in a document you have written, include a copy of
|
|
the License in the document and put the following copyright and
|
|
license notices just after the title page:
|
|
|
|
Copyright (c) YEAR YOUR NAME.
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the GNU Free Documentation License, Version 1.2
|
|
or any later version published by the Free Software Foundation;
|
|
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
|
|
A copy of the license is included in the section entitled "GNU
|
|
Free Documentation License".
|
|
|
|
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
|
|
replace the "with...Texts." line with this:
|
|
|
|
with the Invariant Sections being LIST THEIR TITLES, with the
|
|
Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
|
|
|
|
If you have Invariant Sections without Cover Texts, or some other
|
|
combination of the three, merge those two alternatives to suit the
|
|
situation.
|
|
|
|
If your document contains nontrivial examples of program code, we
|
|
recommend releasing these examples in parallel under your choice of
|
|
free software license, such as the GNU General Public License,
|
|
to permit their use in free software.
|
|
</screen>
|
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</sect1>
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|
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</article>
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