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diff --git a/man/daemon.xml b/man/daemon.xml deleted file mode 100644 index a8bbfc055..000000000 --- a/man/daemon.xml +++ /dev/null @@ -1,765 +0,0 @@ -<?xml version='1.0'?> <!--*-nxml-*--> -<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//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/>. ---> - -<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> - <refentrytitle>daemon</refentrytitle> - <manvolnum>7</manvolnum> - </refmeta> - - <refnamediv> - <refname>daemon</refname> - <refpurpose>Writing and packaging system daemons</refpurpose> - </refnamediv> - - <refsect1> - <title>Description</title> - - <para>A daemon is a service process that runs in the background - and supervises the system or provides functionality to other - processes. Traditionally, daemons are implemented following a - scheme originating in SysV Unix. Modern daemons should follow a - simpler yet more powerful scheme (here called "new-style" - daemons), as implemented by - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. - This manual page covers both schemes, and in particular includes - recommendations for daemons that shall be included in the systemd - init system.</para> - - <refsect2> - <title>SysV Daemons</title> - - <para>When a traditional SysV daemon starts, it should execute - the following steps as part of the initialization. Note that - these steps are unnecessary for new-style daemons (see below), - and should only be implemented if compatibility with SysV is - essential.</para> - - <orderedlist> - <listitem><para>Close all open file descriptors except - standard input, output, and error (i.e. the first three file - descriptors 0, 1, 2). This ensures that no accidentally passed - file descriptor stays around in the daemon process. On Linux, - this is best implemented by iterating through - <filename>/proc/self/fd</filename>, with a fallback of - iterating from file descriptor 3 to the value returned by - <function>getrlimit()</function> for - <constant>RLIMIT_NOFILE</constant>. </para></listitem> - - <listitem><para>Reset all signal handlers to their default. - This is best done by iterating through the available signals - up to the limit of <constant>_NSIG</constant> and resetting - them to <constant>SIG_DFL</constant>.</para></listitem> - - <listitem><para>Reset the signal mask - using - <function>sigprocmask()</function>.</para></listitem> - - <listitem><para>Sanitize the environment block, removing or - resetting environment variables that might negatively impact - daemon runtime.</para></listitem> - - <listitem><para>Call <function>fork()</function>, to create a - background process.</para></listitem> - - <listitem><para>In the child, call - <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>Call <function>exit()</function> in the first - child, so that only the second child (the actual daemon - process) stays around. This ensures that the daemon process is - re-parented to init/PID 1, as all daemons should - be.</para></listitem> - - <listitem><para>In the daemon process, connect - <filename>/dev/null</filename> to standard input, output, and - error.</para></listitem> - - <listitem><para>In the daemon process, reset the umask to 0, - so that the file modes passed to <function>open()</function>, - <function>mkdir()</function> and suchlike directly control the - access mode of the created files and - directories.</para></listitem> - - <listitem><para>In the daemon process, change the current - directory to the root directory (/), in order to avoid that - the daemon involuntarily blocks mount points from being - unmounted.</para></listitem> - - <listitem><para>In the daemon process, write the daemon PID - (as returned by <function>getpid()</function>) to a PID file, - for example <filename>/run/foobar.pid</filename> (for a - hypothetical daemon "foobar") to ensure that the daemon cannot - be started more than once. This must be implemented in - race-free fashion so that the PID file is only updated when it - is verified at the same time that the PID previously stored in - the PID file no longer exists or belongs to a foreign - process.</para></listitem> - - <listitem><para>In the daemon process, drop privileges, if - possible and applicable.</para></listitem> - - <listitem><para>From the daemon process, notify the original - process started that initialization is complete. This can be - implemented via an unnamed pipe or similar communication - channel that is created before the first - <function>fork()</function> and hence available in both the - original and the daemon process.</para></listitem> - - <listitem><para>Call <function>exit()</function> in the - original process. The process that invoked the daemon must be - able to rely on that this <function>exit()</function> happens - after initialization is complete and all external - communication channels are established and - accessible.</para></listitem> - </orderedlist> - - <para>The BSD <function>daemon()</function> function should not - be used, as it implements only a subset of these steps.</para> - - <para>A daemon that needs to provide compatibility with SysV - systems should implement the scheme pointed out above. However, - it is recommended to make this behavior optional and - configurable via a command line argument to ease debugging as - well as to simplify integration into systems using - systemd.</para> - </refsect2> - - <refsect2> - <title>New-Style Daemons</title> - - <para>Modern services for Linux should be implemented as - new-style daemons. This makes it easier to supervise and control - them at runtime and simplifies their implementation.</para> - - <para>For developing a new-style daemon, none of the - initialization steps recommended for SysV daemons need to be - implemented. New-style init systems such as systemd make all of - them redundant. Moreover, since some of these steps interfere - with process monitoring, file descriptor passing and other - 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> - - <para>It is recommended for new-style daemons to implement the - following:</para> - - <orderedlist> - <listitem><para>If <constant>SIGTERM</constant> is received, - shut down the daemon and exit cleanly.</para></listitem> - - <listitem><para>If <constant>SIGHUP</constant> is received, - reload the configuration files, if this - applies.</para></listitem> - - <listitem><para>Provide a correct exit code from the main - daemon process, as this is used by the init system to detect - service errors and problems. It is recommended to follow the - exit code scheme as defined in the <ulink - url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB - recommendations for SysV init - scripts</ulink>.</para></listitem> - - <listitem><para>If possible and applicable, expose the - daemon's control interface via the D-Bus IPC system and grab a - bus name as last step of initialization.</para></listitem> - - <listitem><para>For integration in systemd, provide a - <filename>.service</filename> unit file that carries - information about starting, stopping and otherwise maintaining - the daemon. See - <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details.</para></listitem> - - <listitem><para>As much as possible, rely on the init system's - functionality to limit the access of the daemon to files, - services and other resources, i.e. in the case of systemd, - rely on systemd's resource limit control instead of - implementing your own, rely on systemd's privilege dropping - code instead of implementing it in the daemon, and similar. - See - <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for the available controls.</para></listitem> - - <listitem><para>If D-Bus is used, make your daemon - 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 - 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 - details.</para></listitem> - - <listitem><para>If your daemon provides services to other - local processes or remote clients via a socket, it should be - made socket-activatable following the scheme pointed out - below. Like D-Bus activation, this enables on-demand starting - of services as well as it allows improved parallelization of - service start-up. Also, for state-less protocols (such as - syslog, DNS), a daemon implementing socket-based activation - can be restarted without losing a single request. See below - for details.</para></listitem> - - <listitem><para>If applicable, a daemon should notify the init - system about startup completion or status updates via the - <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> - interface.</para></listitem> - - <listitem><para>Instead of using the - <function>syslog()</function> call to log directly to the - system syslog service, a new-style daemon may choose to simply - log to standard error via <function>fprintf()</function>, - which is then forwarded to syslog by the init system. If log - levels are necessary, these can be encoded by prefixing - individual log lines with strings like - <literal><4></literal> (for log level 4 "WARNING" in the - syslog priority scheme), following a similar style as the - Linux kernel's <function>printk()</function> level system. For - details, see - <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry> - and - <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> - - </orderedlist> - - <para>These recommendations are similar but not identical to the - <ulink - url="https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html">Apple - MacOS X Daemon Requirements</ulink>.</para> - </refsect2> - - </refsect1> - <refsect1> - <title>Activation</title> - - <para>New-style init systems provide multiple additional - mechanisms to activate services, as detailed below. It is common - that services are configured to be activated via more than one - mechanism at the same time. An example for systemd: - <filename>bluetoothd.service</filename> might get activated either - when Bluetooth hardware is plugged in, or when an application - accesses its programming interfaces via D-Bus. Or, a print server - daemon might get activated when traffic arrives at an IPP port, or - when a printer is plugged in, or when a file is queued in the - printer spool directory. Even for services that are intended to be - started on system bootup unconditionally, it is a good idea to - implement some of the various activation schemes outlined below, - in order to maximize parallelization. If a daemon implements a - D-Bus service or listening socket, implementing the full bus and - socket activation scheme allows starting of the daemon with its - clients in parallel (which speeds up boot-up), since all its - communication channels are established already, and no request is - lost because client requests will be queued by the bus system (in - case of D-Bus) or the kernel (in case of sockets) until the - activation is completed.</para> - - <refsect2> - <title>Activation on Boot</title> - - <para>Old-style daemons are usually activated exclusively on - boot (and manually by the administrator) via SysV init scripts, - as detailed in the <ulink - url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB - Linux Standard Base Core Specification</ulink>. This method of - activation is supported ubiquitously on Linux init systems, both - old-style and new-style systems. Among other issues, SysV init - scripts have the disadvantage of involving shell scripts in the - boot process. New-style init systems generally employ updated - versions of activation, both during boot-up and during runtime - and using more minimal service description files.</para> - - <para>In systemd, if the developer or administrator wants to - make sure that a service or other unit is activated - automatically on boot, it is recommended to place a symlink to - the unit file in the <filename>.wants/</filename> directory of - either <filename>multi-user.target</filename> or - <filename>graphical.target</filename>, which are normally used - as boot targets at system startup. See - <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details about the <filename>.wants/</filename> directories, - and - <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> - for details about the two boot targets.</para> - - </refsect2> - - <refsect2> - <title>Socket-Based Activation</title> - - <para>In order to maximize the possible parallelization and - robustness and simplify configuration and development, it is - recommended for all new-style daemons that communicate via - listening sockets to employ socket-based activation. In a - socket-based activation scheme, the creation and binding of the - listening socket as primary communication channel of daemons to - local (and sometimes remote) clients is moved out of the daemon - code and into the init system. Based on per-daemon - configuration, the init system installs the sockets and then - hands them off to the spawned process as soon as the respective - daemon is to be started. Optionally, activation of the service - can be delayed until the first inbound traffic arrives at the - socket to implement on-demand activation of daemons. However, - the primary advantage of this scheme is that all providers and - all consumers of the sockets can be started in parallel as soon - as all sockets are established. In addition to that, daemons can - be restarted with losing only a minimal number of client - transactions, or even any client request at all (the latter is - particularly true for state-less protocols, such as DNS or - syslog), because the socket stays bound and accessible during - the restart, and all requests are queued while the daemon cannot - process them.</para> - - <para>New-style daemons which support socket activation must be - able to receive their sockets from the init system instead of - creating and binding them themselves. For details about the - programming interfaces for this scheme provided by systemd, see - <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry> - and - <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>. - For details about porting existing daemons to socket-based - activation, see below. With minimal effort, it is possible to - implement socket-based activation in addition to traditional - internal socket creation in the same codebase in order to - support both new-style and old-style init systems from the same - daemon binary.</para> - - <para>systemd implements socket-based activation via - <filename>.socket</filename> units, which are described in - <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>. - When configuring socket units for socket-based activation, it is - essential that all listening sockets are pulled in by the - special target unit <filename>sockets.target</filename>. It is - recommended to place a - <varname>WantedBy=sockets.target</varname> directive in the - <literal>[Install]</literal> section to automatically add such a - dependency on installation of a socket unit. Unless - <varname>DefaultDependencies=no</varname> is set, the necessary - ordering dependencies are implicitly created for all socket - units. For more information about - <filename>sockets.target</filename>, see - <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>. - It is not necessary or recommended to place any additional - dependencies on socket units (for example from - <filename>multi-user.target</filename> or suchlike) when one is - installed in <filename>sockets.target</filename>.</para> - </refsect2> - - <refsect2> - <title>Bus-Based Activation</title> - - <para>When the D-Bus IPC system is used for communication with - clients, new-style daemons should employ bus activation so that - they are automatically activated when a client application - accesses their IPC interfaces. This is configured in D-Bus - service files (not to be confused with systemd service unit - files!). To ensure that D-Bus uses systemd to start-up and - maintain the daemon, use the <varname>SystemdService=</varname> - directive in these service files to configure the matching - systemd service for a D-Bus service. e.g.: For a D-Bus service - whose D-Bus activation file is named - <filename>org.freedesktop.RealtimeKit.service</filename>, make - sure to set - <varname>SystemdService=rtkit-daemon.service</varname> in that - file to bind it to the systemd service - <filename>rtkit-daemon.service</filename>. This is needed to - make sure that the daemon is started in a race-free fashion when - activated via multiple mechanisms simultaneously.</para> - </refsect2> - - <refsect2> - <title>Device-Based Activation</title> - - <para>Often, daemons that manage a particular type of hardware - should be activated only when the hardware of the respective - kind is plugged in or otherwise becomes available. In a - new-style init system, it is possible to bind activation to - hardware plug/unplug events. In systemd, kernel devices - appearing in the sysfs/udev device tree can be exposed as units - if they are tagged with the string <literal>systemd</literal>. - Like any other kind of unit, they may then pull in other units - when activated (i.e. plugged in) and thus implement device-based - activation. systemd dependencies may be encoded in the udev - database via the <varname>SYSTEMD_WANTS=</varname> property. See - <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details. Often, it is nicer to pull in services from devices - only indirectly via dedicated targets. Example: Instead of - pulling in <filename>bluetoothd.service</filename> from all the - various bluetooth dongles and other hardware available, pull in - bluetooth.target from them and - <filename>bluetoothd.service</filename> from that target. This - provides for nicer abstraction and gives administrators the - option to enable <filename>bluetoothd.service</filename> via - controlling a <filename>bluetooth.target.wants/</filename> - symlink uniformly with a command like <command>enable</command> - of - <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> - instead of manipulating the udev ruleset.</para> - </refsect2> - - <refsect2> - <title>Path-Based Activation</title> - - <para>Often, runtime of daemons processing spool files or - directories (such as a printing system) can be delayed until - these file system objects change state, or become non-empty. - New-style init systems provide a way to bind service activation - to file system changes. systemd implements this scheme via - path-based activation configured in <filename>.path</filename> - units, as outlined in - <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> - </refsect2> - - <refsect2> - <title>Timer-Based Activation</title> - - <para>Some daemons that implement clean-up jobs that are - intended to be executed in regular intervals benefit from - timer-based activation. In systemd, this is implemented via - <filename>.timer</filename> units, as described in - <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> - </refsect2> - - <refsect2> - <title>Other Forms of Activation</title> - - <para>Other forms of activation have been suggested and - implemented in some systems. However, there are often simpler or - better alternatives, or they can be put together of combinations - of the schemes above. Example: Sometimes, it appears useful to - start daemons or <filename>.socket</filename> units when a - specific IP address is configured on a network interface, - because network sockets shall be bound to the address. However, - an alternative to implement this is by utilizing the Linux - <constant>IP_FREEBIND</constant> socket option, as accessible - via <varname>FreeBind=yes</varname> in systemd socket files (see - <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details). This option, when enabled, allows sockets to be - bound to a non-local, not configured IP address, and hence - allows bindings to a particular IP address before it actually - becomes available, making such an explicit dependency to the - configured address redundant. Another often suggested trigger - for service activation is low system load. However, here too, a - more convincing approach might be to make proper use of features - of the operating system, in particular, the CPU or IO scheduler - of Linux. Instead of scheduling jobs from userspace based on - monitoring the OS scheduler, it is advisable to leave the - scheduling of processes to the OS scheduler itself. systemd - provides fine-grained access to the CPU and IO schedulers. If a - process executed by the init system shall not negatively impact - the amount of CPU or IO bandwidth available to other processes, - it should be configured with - <varname>CPUSchedulingPolicy=idle</varname> and/or - <varname>IOSchedulingClass=idle</varname>. Optionally, this may - be combined with timer-based activation to schedule background - jobs during runtime and with minimal impact on the system, and - remove it from the boot phase itself.</para> - </refsect2> - - </refsect1> - <refsect1> - <title>Integration with Systemd</title> - - <refsect2> - <title>Writing Systemd Unit Files</title> - - <para>When writing systemd unit files, it is recommended to - consider the following suggestions:</para> - - <orderedlist> - <listitem><para>If possible, do not use the - <varname>Type=forking</varname> setting in service files. But - if you do, make sure to set the PID file path using - <varname>PIDFile=</varname>. See - <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details.</para></listitem> - - <listitem><para>If your daemon registers a D-Bus name on the - bus, make sure to use <varname>Type=dbus</varname> in the - service file if possible.</para></listitem> - - <listitem><para>Make sure to set a good human-readable - description string with - <varname>Description=</varname>.</para></listitem> - - <listitem><para>Do not disable - <varname>DefaultDependencies=</varname>, unless you really - know what you do and your unit is involved in early boot or - late system shutdown.</para></listitem> - - <listitem><para>Normally, little if any dependencies should - need to be defined explicitly. However, if you do configure - explicit dependencies, only refer to unit names listed on - <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> - or names introduced by your own package to keep the unit file - operating system-independent.</para></listitem> - - <listitem><para>Make sure to include an - <literal>[Install]</literal> section including installation - information for the unit file. See - <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for details. To activate your service on boot, make sure to - add a <varname>WantedBy=multi-user.target</varname> or - <varname>WantedBy=graphical.target</varname> directive. To - activate your socket on boot, make sure to add - <varname>WantedBy=sockets.target</varname>. Usually, you also - want to make sure that when your service is installed, your - socket is installed too, hence add - <varname>Also=foo.socket</varname> in your service file - <filename>foo.service</filename>, for a hypothetical program - <filename>foo</filename>.</para></listitem> - - </orderedlist> - </refsect2> - - <refsect2> - <title>Installing Systemd Service Files</title> - - <para>At the build installation time (e.g. <command>make - install</command> during package build), packages are - recommended to install their systemd unit files in the directory - returned by <command>pkg-config systemd - --variable=systemdsystemunitdir</command> (for system services) - or <command>pkg-config systemd - --variable=systemduserunitdir</command> (for user services). - This will make the services available in the system on explicit - request but not activate them automatically during boot. - Optionally, during package installation (e.g. <command>rpm - -i</command> by the administrator), symlinks should be created - in the systemd configuration directories via the - <command>enable</command> command of the - <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> - tool to activate them automatically on boot.</para> - - <para>Packages using - <citerefentry project='die-net'><refentrytitle>autoconf</refentrytitle><manvolnum>1</manvolnum></citerefentry> - are recommended to use a configure script - excerpt like the following to determine the - unit installation path during source - configuration:</para> - - <programlisting>PKG_PROG_PKG_CONFIG -AC_ARG_WITH([systemdsystemunitdir], - [AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files])],, - [with_systemdsystemunitdir=auto]) -AS_IF([test "x$with_systemdsystemunitdir" = "xyes" -o "x$with_systemdsystemunitdir" = "xauto"], [ - def_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd) - - AS_IF([test "x$def_systemdsystemunitdir" = "x"], - [AS_IF([test "x$with_systemdsystemunitdir" = "xyes"], - [AC_MSG_ERROR([systemd support requested but pkg-config unable to query systemd package])]) - with_systemdsystemunitdir=no], - [with_systemdsystemunitdir="$def_systemdsystemunitdir"])]) -AS_IF([test "x$with_systemdsystemunitdir" != "xno"], - [AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])]) -AM_CONDITIONAL([HAVE_SYSTEMD], [test "x$with_systemdsystemunitdir" != "xno"])</programlisting> - - <para>This snippet allows automatic - installation of the unit files on systemd - machines, and optionally allows their - installation even on machines lacking - systemd. (Modification of this snippet for the - user unit directory is left as an exercise for the - reader.)</para> - - <para>Additionally, to ensure that - <command>make distcheck</command> continues to - work, it is recommended to add the following - to the top-level <filename>Makefile.am</filename> - file in - <citerefentry project='die-net'><refentrytitle>automake</refentrytitle><manvolnum>1</manvolnum></citerefentry>-based - projects:</para> - - <programlisting>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> - - <programlisting>if HAVE_SYSTEMD -systemdsystemunit_DATA = \ - foobar.socket \ - foobar.service -endif</programlisting> - - <para>In the - <citerefentry project='die-net'><refentrytitle>rpm</refentrytitle><manvolnum>8</manvolnum></citerefentry> - <filename>.spec</filename> file, use snippets like the following - to enable/disable the service during - installation/deinstallation. This makes use of the RPM macros - shipped along systemd. Consult the packaging guidelines of your - distribution for details and the equivalent for other package - managers.</para> - - <para>At the top of the file:</para> - - <programlisting>BuildRequires: systemd -%{?systemd_requires}</programlisting> - - <para>And as scriptlets, further down:</para> - - <programlisting>%post -%systemd_post foobar.service foobar.socket - -%preun -%systemd_preun foobar.service foobar.socket - -%postun -%systemd_postun</programlisting> - - <para>If the service shall be restarted during upgrades, replace - the <literal>%postun</literal> scriptlet above with the - following:</para> - - <programlisting>%postun -%systemd_postun_with_restart foobar.service</programlisting> - - <para>Note that <literal>%systemd_post</literal> and - <literal>%systemd_preun</literal> expect the names of all units - that are installed/removed as arguments, separated by spaces. - <literal>%systemd_postun</literal> expects no arguments. - <literal>%systemd_postun_with_restart</literal> expects the - units to restart as arguments.</para> - - <para>To facilitate upgrades from a package version that shipped - only SysV init scripts to a package version that ships both a - SysV init script and a native systemd service file, use a - fragment like the following:</para> - - <programlisting>%triggerun -- foobar < 0.47.11-1 -if /sbin/chkconfig --level 5 foobar ; then - /bin/systemctl --no-reload enable foobar.service foobar.socket >/dev/null 2>&1 || : -fi</programlisting> - - <para>Where 0.47.11-1 is the first package version that includes - the native unit file. This fragment will ensure that the first - time the unit file is installed, it will be enabled if and only - if the SysV init script is enabled, thus making sure that the - enable status is not changed. Note that - <command>chkconfig</command> is a command specific to Fedora - which can be used to check whether a SysV init script is - enabled. Other operating systems will have to use different - commands here.</para> - </refsect2> - </refsect1> - - <refsect1> - <title>Porting Existing Daemons</title> - - <para>Since new-style init systems such as systemd are compatible - with traditional SysV init systems, it is not strictly necessary - to port existing daemons to the new style. However, doing so - offers additional functionality to the daemons as well as - simplifying integration into new-style init systems.</para> - - <para>To port an existing SysV compatible daemon, the following - steps are recommended:</para> - - <orderedlist> - <listitem><para>If not already implemented, add an optional - command line switch to the daemon to disable daemonization. This - is useful not only for using the daemon in new-style init - systems, but also to ease debugging.</para></listitem> - - <listitem><para>If the daemon offers interfaces to other - software running on the local system via local - <constant>AF_UNIX</constant> sockets, consider implementing - socket-based activation (see above). Usually, a minimal patch is - sufficient to implement this: Extend the socket creation in the - daemon code so that - <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry> - is checked for already passed sockets first. If sockets are - passed (i.e. when <function>sd_listen_fds()</function> returns a - positive value), skip the socket creation step and use the - passed sockets. Secondly, ensure that the file system socket - nodes for local <constant>AF_UNIX</constant> sockets used in the - socket-based activation are not removed when the daemon shuts - down, if sockets have been passed. Third, if the daemon normally - closes all remaining open file descriptors as part of its - initialization, the sockets passed from the init system must be - spared. Since new-style init systems guarantee that no left-over - file descriptors are passed to executed processes, it might be a - good choice to simply skip the closing of all remaining open - file descriptors if sockets are passed.</para></listitem> - - <listitem><para>Write and install a systemd unit file for the - service (and the sockets if socket-based activation is used, as - well as a path unit file, if the daemon processes a spool - directory), see above for details.</para></listitem> - - <listitem><para>If the daemon exposes interfaces via D-Bus, - write and install a D-Bus activation file for the service, see - above for details.</para></listitem> - </orderedlist> - </refsect1> - - <refsect1> - <title>Placing Daemon Data</title> - - <para>It is recommended to follow the general guidelines for - placing package files, as discussed in - <citerefentry><refentrytitle>file-hierarchy</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> - </refsect1> - - <refsect1> - <title>See Also</title> - <para> - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, - <citerefentry><refentrytitle>file-hierarchy</refentrytitle><manvolnum>7</manvolnum></citerefentry> - </para> - </refsect1> - -</refentry> |