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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+<!ENTITY mdash "—" >
+]>
+
+ <chapter id="kea-lfc">
+ <title>The LFC process</title>
+
+ <section id="kea-lfc-overview">
+ <title>Overview</title>
+ <para><command>kea-lfc</command> is a service process that removes
+ redundant infomation from the files used to provide persistent storage
+ for the memfile data base backend. This service is written to run as a
+ stand alone process.
+ </para>
+ <para>While <command>kea-lfc</command> can be started externally it should
+ be started by the Kea DHCP servers.
+ </para>
+ <para>The process operates on a set of files, using them for input and output
+ of the lease entries and to indicate where it is in the process in case of an
+ interruption. Currently the caller must supply names for all of the files, in
+ the future this requirement may be relaxed with the process getting the names
+ from either the config file or from defaults.
+ </para>
+ </section>
+
+ <section id="kea-lfc-usage">
+ <title>Command Line Options</title>
+ <para><command>kea-lfc</command> is run as follows:
+<screen>
+kea-lfc [-4 | -6] -c config-file -p pid-file -x previous-file -i copy-file -o output-file -f finish-file
+</screen>
+ </para>
+
+ <para>The argument <command>-4</command> or <command>-6</command> selects the protocol
+ version of the lease files.
+ </para>
+
+ <para>The <command>-c</command> argument specifies the configuration file. This is
+ required, but not currently used by the process.
+ </para>
+
+ <para>The <command>-p</command> argument specifies the PID file. When the
+ <command>kea-lfc</command> process starts it attempts to determine if another
+ instance of the process is already running by examining the pid file. If one
+ is running it aborts the new process. If one isn't running it writes its
+ pid into the pid file.
+ </para>
+
+ <para>The other filenames specify where the <command>kea-lfc</command> process
+ should look for input, write its output and use for bookkeeping.
+
+ <itemizedlist>
+ <listitem><simpara>
+ <command>previous</command> —
+ When <command>kea-lfc</command> starts this
+ is the result of any previous run of <command>kea-lfc</command>.
+ When <command>kea-lfc</command> finishes it is the result of this run.
+ If <command>kea-lfc</command> is interrupted before compelting
+ this file may not exist.
+ </simpara></listitem>
+
+ <listitem><simpara>
+ <command>input</command> —
+ Before the DHCP server invokes <command>kea-lfc</command> it will
+ copy the current lease file here and then call <command>kea-lfc</command>
+ with this file.
+ </simpara></listitem>
+
+ <listitem><simpara>
+ <command>output</command> —
+ The temporary file <command>kea-lfc</command> should use to write the leases.
+ Upon completion of writing this this file it will be moved to the finish file
+ (see below).
+ </simpara></listitem>
+
+ <listitem><simpara>
+ <command>finish</command> —
+ Another temporary file <command>kea-lfc</command> uses for bookkeeping. When
+ <command>kea-lfc</command> completes writing the outputfile it moves it to this
+ file name. After <command>kea-lfc</command> finishes deleting the other files
+ (previous and input) it moves this file to previous lease file. By moving the
+ files in this fashion the <command>kea-lfc</command> and the DHCP server
+ processes can determine the correct file to use even if one of the
+ processes was interrupted before completing its task.
+ </simpara></listitem>
+
+ </itemizedlist>
+ </para>
+
+ <para>There are several additional arguments mostly for debugging purposes.
+ <command>-d</command> Sets the logging level to debug. <command>-v</command> and
+ <command>-V</command> print out version stamps with <command>-V</command> providing
+ a longer form. <command>-h</command> prints out the usage string.
+ </para>
+
+ </section>
+ </chapter>
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