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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
<!ENTITY daemon "stafd">
<!ENTITY deamondesc "STorage Appliance Finder">
<!ENTITY control "stafctl">
]>
<!--
SPDX-License-Identifier: Apache-2.0
Copyright (c) 2021, Dell Inc. or its subsidiaries. All rights reserved.
-->
<refentry id="&daemon;" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>&daemon;</title>
<productname>nvme-stas</productname>
<author>
<personname>
<honorific>Mr</honorific>
<firstname>Martin</firstname>
<surname>Belanger</surname>
</personname>
<affiliation>
<orgname>Dell, Inc.</orgname>
</affiliation>
</author>
</refentryinfo>
<refmeta>
<refentrytitle>&daemon;</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>&daemon;</refname>
<refpurpose>&deamondesc;</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>&daemon;</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>&daemon;</command>
is a system daemon that can be used to automatically locate and
connect to NVMe-oF Discovery Controllers using mDNS service discovery.
It can also be manually configured with
<citerefentry>
<refentrytitle>&daemon;.conf</refentrytitle>
<manvolnum>5</manvolnum>
</citerefentry>
to connect to Discovery Controllers that cannot be located using
mDNS.
</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<xi:include href="standard-options.xml" xpointer="help"/>
<xi:include href="standard-options.xml" xpointer="version"/>
</variablelist>
<varlistentry>
<term><option>-fFILE</option></term>
<term><option>--conf-file=FILE</option></term>
<listitem>
<para>
Specify a different configuration file than
<citerefentry>
<refentrytitle>&daemon;.conf</refentrytitle>
<manvolnum>5</manvolnum>
</citerefentry>
(default: <filename>/etc/stas/&daemon;.conf</filename>).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s</option></term>
<term><option>--syslog</option></term>
<listitem>
<para>
Send messages to syslog instead of stdout. Use this when
running &daemon; as a daemon. (default: <literal>false</literal>).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--tron</option></term>
<listitem>
<para>Trace ON. (default: <literal>false</literal>)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--idl=FILE</option></term>
<listitem>
<para>Print D-Bus IDL to FILE and exit.</para>
</listitem>
</varlistentry>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>
On success, 0 is returned, a non-zero failure code otherwise.
</para>
</refsect1>
<refsect1>
<title>Daemonization</title>
<para>
&daemon; is managed by <code>systemd</code>. The following
operations are supported:
</para>
<table frame='all'>
<tgroup cols="2" align='left' colsep='1' rowsep='1'>
<thead>
<row>
<entry>Command</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><programlisting>$ systemctl start &daemon; </programlisting></entry>
<entry>Start daemon.</entry>
</row>
<row>
<entry><programlisting>$ systemctl stop &daemon; </programlisting></entry>
<entry>Stop daemon. The <code>SIGTERM</code> signal is used to tell the daemon to stop.</entry>
</row>
<row>
<entry><programlisting>$ systemctl restart &daemon; </programlisting></entry>
<entry>Effectively a <code>stop</code> + <code>start</code>.</entry>
</row>
<row>
<entry><programlisting>$ systemctl reload &daemon; </programlisting></entry>
<entry>Reload configuration. This is done in real time without restarting the daemon. The <code>SIGHUP</code> signal is used to tell the daemon to reload its configuration file. Note that configuration parameters that affect connections (e.g. <code>kato</code>), will not apply to existing connections. Only connections established after the configuration was changed will utilize the new configuration parameters.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
<title>Design</title>
<para>
<command>&daemon;</command> use the <code>GLib</code> main loop.
The <code>GLib</code> Python module provides several low-level
building blocks that <command>&daemon;</command> requires. In
addition, many Python modules "play nice" with <code>GLib</code>
such as <code>dasbus</code> (D-Bus package) and <code>pyudev</code>
(UDev package). <code>GLib</code> also provides additional components
such as timers, signal handlers, and much more.
</para>
<para>
<command>&daemon;</command> connects to the <code>avahi-daemon</code>
using D-Bus. The <code>avahi-daemon</code>, or simply
<emphasis>Avahi</emphasis>, is an mDNS discovery service used for
zero-configuration networking (zeroconf). <command>&daemon;</command>
registers with Avahi to automatically locate Central Discovery
Controllers (CDC) and Direct Discovery Controllers (DDC). When Avahi
finds Discovery Controllers (DC), it notifies <command>&daemon;</command>
which connects to the DC with the help of the <code>libnvme</code> library.
Once a connection to a DC is established, <command>&daemon;</command>
can retrieve the <emphasis>discovery log pages</emphasis> from
that DC and cache them in memory.
</para>
</refsect1>
<refsect1>
<title>Configuration</title>
<para>
<command>&daemon;</command> can automatically locate discovery
controllers (DC) with the help of Avahi and connect to them. However,
<command>&daemon;</command> can also operate in a non-automatic
mode based on manually entered configuration. In other words,
DCs can be entered in a configuration named
<filename>/etc/stas/&daemon;.conf</filename>.
This configuration file also provides additional parameters, such
as log-level attributes used for debugging purposes.
</para>
</refsect1>
<refsect1>
<title>D-Bus API</title>
<para>
The interface to <command>&daemon;</command> is D-Bus.
This allows other programs, such as <command>&control;</command>,
to communicate with <command>&daemon;</command>. The D-Bus address
is <code>org.nvmexpress.staf</code>.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry>
<refentrytitle>&daemon;.conf</refentrytitle>
<manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>&daemon;.service</refentrytitle>
<manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>stafctl</refentrytitle>
<manvolnum>1</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>org.nvmexpress.staf</refentrytitle>
<manvolnum>5</manvolnum>
</citerefentry>.
</para>
</refsect1>
</refentry>