<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="daemon">
<refentryinfo>
<title>daemon</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<function>setsid()</function> to detach from any terminal and
create an independent session.</para></listitem>
- <listitem><para>In the child, call <function>fork()</function>
- again, to ensure that the daemon can never re-acquire a
- terminal again.</para></listitem>
+ <listitem><para>In the child, call <function>fork()</function> again, to ensure that the daemon can
+ never re-acquire a terminal again. (This relevant if the program — and all its dependencies — does
+ not carefully specify `O_NOCTTY` on each and every single `open()` call that might potentially open a
+ TTY device node.)</para></listitem>
<listitem><para>Call <function>exit()</function> in the first
child, so that only the second child (the actual daemon
functionality of the init system, it is recommended not to
execute them when run as new-style service.</para>
- <para>Note that new-style init systems guarantee execution of
- daemon processes in a clean process context: it is guaranteed
- that the environment block is sanitized, that the signal
- handlers and mask is reset and that no left-over file
- descriptors are passed. Daemons will be executed in their own
- session, with standard input/output/error connected to
- <filename>/dev/null</filename> unless otherwise configured. The
- umask is reset.
+ <para>Note that new-style init systems guarantee execution of daemon processes in a clean process context: it is
+ guaranteed that the environment block is sanitized, that the signal handlers and mask is reset and that no
+ left-over file descriptors are passed. Daemons will be executed in their own session, with standard input
+ connected to <filename>/dev/null</filename> and standard output/error connected to the
+ <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ logging service, unless otherwise configured. The umask is reset.
</para>
<para>It is recommended for new-style daemons to implement the
bus-activatable by supplying a D-Bus service activation
configuration file. This has multiple advantages: your daemon
may be started lazily on-demand; it may be started in parallel
- to other daemons requiring it -- which maximizes
+ to other daemons requiring it — which maximizes
parallelization and boot-up speed; your daemon can be
restarted on failure without losing any bus requests, as the
bus queues requests for activatable services. See below for
and
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+ <listitem><para>As new-style daemons are invoked without a controlling TTY (but as their own session
+ leaders) care should be taken to always specify `O_NOCTTY` on `open()` calls that possibly reference
+ a TTY device node, so that no controlling TTY is accidentally acquired.</para></listitem>
+
</orderedlist>
<para>These recommendations are similar but not identical to the
</refsect1>
<refsect1>
- <title>Integration with Systemd</title>
+ <title>Integration with systemd</title>
<refsect2>
- <title>Writing Systemd Unit Files</title>
+ <title>Writing systemd Unit Files</title>
<para>When writing systemd unit files, it is recommended to
consider the following suggestions:</para>
</refsect2>
<refsect2>
- <title>Installing Systemd Service Files</title>
+ <title>Installing systemd Service Files</title>
<para>At the build installation time (e.g. <command>make
install</command> during package build), packages are
<citerefentry project='die-net'><refentrytitle>automake</refentrytitle><manvolnum>1</manvolnum></citerefentry>-based
projects:</para>
- <programlisting>DISTCHECK_CONFIGURE_FLAGS = \
+ <programlisting>AM_DISTCHECK_CONFIGURE_FLAGS = \
--with-systemdsystemunitdir=$$dc_install_base/$(systemdsystemunitdir)</programlisting>
<para>Finally, unit files should be installed in the system with an automake excerpt like the following:</para>
projects / thirdparty / systemd.git / blobdiff