/mandos/release

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237.2.198 by teddy at bsnet
* Makefile (DOCS): Added "plymouth.8mandos".
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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	"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY COMMANDNAME "plymouth">
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<!ENTITY TIMESTAMP "2010-09-23">
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<!ENTITY % common SYSTEM "../common.ent">
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%common;
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]>
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<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
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  <refentryinfo>
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    <title>Mandos Manual</title>
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    <!-- NWalsh’s docbook scripts use this to generate the footer: -->
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    <productname>Mandos</productname>
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    <productnumber>&version;</productnumber>
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    <date>&TIMESTAMP;</date>
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    <authorgroup>
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      <author>
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	<firstname>Björn</firstname>
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	<surname>Påhlsson</surname>
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	<address>
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	  <email>belorn@fukt.bsnet.se</email>
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	</address>
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      </author>
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      <author>
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	<firstname>Teddy</firstname>
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	<surname>Hogeborn</surname>
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	<address>
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	  <email>teddy@fukt.bsnet.se</email>
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	</address>
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      </author>
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    </authorgroup>
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    <copyright>
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      <year>2008</year>
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      <year>2009</year>
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      <holder>Teddy Hogeborn</holder>
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      <holder>Björn Påhlsson</holder>
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    </copyright>
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    <xi:include href="../legalnotice.xml"/>
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  </refentryinfo>
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  <refmeta>
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    <refentrytitle>&COMMANDNAME;</refentrytitle>
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    <manvolnum>8mandos</manvolnum>
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  </refmeta>
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  <refnamediv>
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    <refname><command>&COMMANDNAME;</command></refname>
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    <refpurpose>Mandos plugin to use plymouth to get a
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    password.</refpurpose>
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  </refnamediv>
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  <refsynopsisdiv>
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    <cmdsynopsis>
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      <command>&COMMANDNAME;</command>
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    </cmdsynopsis>
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  </refsynopsisdiv>
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  <refsect1 id="description">
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    <title>DESCRIPTION</title>
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    <para>
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      This program prompts for a password using <citerefentry>
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      <refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum>
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      </citerefentry> and outputs any given password to standard
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      output.  If no <citerefentry><refentrytitle
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      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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      process can be found, this program will immediately exit with an
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      exit code indicating failure.
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    </para>
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    <para>
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      This program is not very useful on its own.  This program is
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      really meant to run as a plugin in the <application
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      >Mandos</application> client-side system, where it is used as a
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      fallback and alternative to retrieving passwords from a
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      <application >Mandos</application> server.
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    </para>
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    <para>
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      If this program is killed (presumably by
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      <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry> because some other
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      plugin provided the password), it cannot tell <citerefentry>
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      <refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum>
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      </citerefentry> to abort requesting a password, because
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      <citerefentry><refentrytitle>plymouth</refentrytitle>
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      <manvolnum>8</manvolnum></citerefentry> does not support this.
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      Therefore, this program will then <emphasis>kill</emphasis> the
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      running <citerefentry><refentrytitle>plymouth</refentrytitle>
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      <manvolnum>8</manvolnum></citerefentry> process and start a
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      <emphasis>new</emphasis> one using the same command line
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      arguments as the old one was using.
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    </para>
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  </refsect1>
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  <refsect1 id="options">
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    <title>OPTIONS</title>
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    <para>
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      This program takes no options.
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    </para>
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  </refsect1>
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  <refsect1 id="exit_status">
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    <title>EXIT STATUS</title>
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    <para>
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      If exit status is 0, the output from the program is the password
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      as it was read.  Otherwise, if exit status is other than 0, the
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      program was interrupted or encountered an error, and any output
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      so far could be corrupt and/or truncated, and should therefore
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      be ignored.
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    </para>
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  </refsect1>
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  <refsect1 id="environment">
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    <title>ENVIRONMENT</title>
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    <variablelist>
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      <varlistentry>
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	<term><envar>cryptsource</envar></term>
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	<term><envar>crypttarget</envar></term>
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	<listitem>
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	  <para>
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	    If set, these environment variables will be assumed to
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	    contain the source device name and the target device
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	    mapper name, respectively, and will be shown as part of
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	    the prompt.
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	</para>
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	<para>
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	  These variables will normally be inherited from
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	  <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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	  <manvolnum>8mandos</manvolnum></citerefentry>, which will
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	  normally have inherited them from
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	  <filename>/scripts/local-top/cryptroot</filename> in the
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	  initial <acronym>RAM</acronym> disk environment, which will
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	  have set them from parsing kernel arguments and
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	  <filename>/conf/conf.d/cryptroot</filename> (also in the
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	  initial RAM disk environment), which in turn will have been
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	  created when the initial RAM disk image was created by
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	  <filename
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	  >/usr/share/initramfs-tools/hooks/cryptroot</filename>, by
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	  extracting the information of the root file system from
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	  <filename >/etc/crypttab</filename>.
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	</para>
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	<para>
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	  This behavior is meant to exactly mirror the behavior of
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	  <command>askpass</command>, the default password prompter.
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	</para>
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	</listitem>
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      </varlistentry>
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    </variablelist>
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  </refsect1>
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  <refsect1 id="files">
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    <title>FILES</title>
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    <variablelist>
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      <varlistentry>
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	<term><filename>/bin/plymouth</filename></term>
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	<listitem>
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	  <para>
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	    This is the command run to retrieve a password from
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	    <citerefentry><refentrytitle>plymouth</refentrytitle>
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	    <manvolnum>8</manvolnum></citerefentry>.
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	  </para>
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	</listitem>
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      </varlistentry>
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      <varlistentry>
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	<term><filename>/proc</filename></term>
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	<listitem>
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	  <para>
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	    To find the running <citerefentry><refentrytitle
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	    >plymouth</refentrytitle><manvolnum>8</manvolnum>
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	    </citerefentry>, this directory will be searched for
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	    numeric entries which will be assumed to be directories.
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	    In all those directories, the <filename>exe</filename> and
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	    <filename>cmdline</filename> entries will be used to
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	    determine the name of the running binary, effective user
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	    and group <abbrev>ID</abbrev>, and the command line
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	    arguments.  See <citerefentry><refentrytitle
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	    >proc</refentrytitle><manvolnum>5</manvolnum>
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	    </citerefentry>.
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	  </para>
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	</listitem>
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      </varlistentry>
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      <varlistentry>
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	<term><filename>/sbin/plymouthd</filename></term>
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	<listitem>
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	  <para>
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	    This is the name of the binary which will be searched for
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	    in the process list.  See <citerefentry><refentrytitle
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	    >plymouth</refentrytitle><manvolnum>8</manvolnum>
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	    </citerefentry>.
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	  </para>
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	</listitem>
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      </varlistentry>
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    </variablelist>
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  </refsect1>
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  <refsect1 id="bugs">
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    <title>BUGS</title>
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    <para>
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      Killing the <citerefentry><refentrytitle
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      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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      daemon and starting a new one is ugly, but necessary as long as
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      it does not support aborting a password request.
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    </para>
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  </refsect1>
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  <refsect1 id="example">
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    <title>EXAMPLE</title>
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    <para>
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      Note that normally, this program will not be invoked directly,
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      but instead started by the Mandos <citerefentry><refentrytitle
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      >plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
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      </citerefentry>.
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    </para>
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    <informalexample>
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      <para>
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	This program takes no options.
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      </para>
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      <para>
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	<userinput>&COMMANDNAME;</userinput>
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      </para>
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    </informalexample>
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  </refsect1>
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  <refsect1 id="security">
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    <title>SECURITY</title>
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    <para>
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      If this program is killed by a signal, it will kill the process
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      <abbrev>ID</abbrev> which at the start of this program was
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      determined to run <citerefentry><refentrytitle
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      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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      as root (see also <xref linkend="files"/>).  There is a very
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      slight risk that, in the time between those events, that process
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      <abbrev>ID</abbrev> was freed and then taken up by another
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      process; the wrong process would then be killed.  Now, this
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      program can only be killed by the user who started it; see
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      <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>.  This program
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      should therefore be started by a completely separate
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      non-privileged user, and no other programs should be allowed to
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      run as that special user.  This means that it is not recommended
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      to use the user "nobody" to start this program, as other
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      possibly less trusted programs could be running as "nobody", and
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      they would then be able to kill this program, triggering the
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      killing of the process <abbrev>ID</abbrev> which may or may not
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      be <citerefentry><refentrytitle>plymouth</refentrytitle>
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      <manvolnum>8</manvolnum></citerefentry>.
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    </para>
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    <para>
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      The only other thing that could be considered worthy of note is
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      this:  This program is meant to be run by <citerefentry>
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      <refentrytitle>plugin-runner</refentrytitle><manvolnum
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      >8mandos</manvolnum></citerefentry>, and will, when run
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      standalone, outside, in a normal environment, immediately output
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      on its standard output any presumably secret password it just
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      received.  Therefore, when running this program standalone
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      (which should never normally be done), take care not to type in
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      any real secret password by force of habit, since it would then
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      immediately be shown as output.
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    </para>
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  </refsect1>
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  <refsect1 id="see_also">
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    <title>SEE ALSO</title>
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    <para>
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      <citerefentry><refentrytitle>crypttab</refentrytitle>
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      <manvolnum>5</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>proc</refentrytitle>
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      <manvolnum>5</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>plymouth</refentrytitle>
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      <manvolnum>8</manvolnum></citerefentry>
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    </para>
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  </refsect1>
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</refentry>
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