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diff --git a/man/daemon.html b/man/daemon.html deleted file mode 100644 index 1a65435e63..0000000000 --- a/man/daemon.html +++ /dev/null @@ -1,498 +0,0 @@ -<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>daemon</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style> - a.headerlink { - color: #c60f0f; - font-size: 0.8em; - padding: 0 4px 0 4px; - text-decoration: none; - visibility: hidden; - } - - a.headerlink:hover { - background-color: #c60f0f; - color: white; - } - - h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink { - visibility: visible; - } - </style><a href="index.html">Index </a>· - <a href="systemd.directives.html">Directives </a>· - <a href="../python-systemd/index.html">Python </a>· - - <span style="float:right">systemd 221</span><hr><div class="refentry"><a name="daemon"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>daemon — Writing and packaging system daemons</p></div><div class="refsect1"><a name="idm47144714447520"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>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 - <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>. - This manual page covers both schemes, and in particular includes - recommendations for daemons that shall be included in the systemd - init system.</p><div class="refsect2"><a name="idm47144714445072"></a><h3 id="SysV Daemons">SysV Daemons<a class="headerlink" title="Permalink to this headline" href="#SysV%20Daemons">¶</a></h3><p>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.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>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 - <code class="filename">/proc/self/fd</code>, with a fallback of - iterating from file descriptor 3 to the value returned by - <code class="function">getrlimit()</code> for - <code class="constant">RLIMIT_NOFILE</code>. </p></li><li class="listitem"><p>Reset all signal handlers to their default. - This is best done by iterating through the available signals - up to the limit of <code class="constant">_NSIG</code> and resetting - them to <code class="constant">SIG_DFL</code>.</p></li><li class="listitem"><p>Reset the signal mask - using - <code class="function">sigprocmask()</code>.</p></li><li class="listitem"><p>Sanitize the environment block, removing or - resetting environment variables that might negatively impact - daemon runtime.</p></li><li class="listitem"><p>Call <code class="function">fork()</code>, to create a - background process.</p></li><li class="listitem"><p>In the child, call - <code class="function">setsid()</code> to detach from any terminal and - create an independent session.</p></li><li class="listitem"><p>In the child, call <code class="function">fork()</code> - again, to ensure that the daemon can never re-acquire a - terminal again.</p></li><li class="listitem"><p>Call <code class="function">exit()</code> 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.</p></li><li class="listitem"><p>In the daemon process, connect - <code class="filename">/dev/null</code> to standard input, output, and - error.</p></li><li class="listitem"><p>In the daemon process, reset the umask to 0, - so that the file modes passed to <code class="function">open()</code>, - <code class="function">mkdir()</code> and suchlike directly control the - access mode of the created files and - directories.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>In the daemon process, write the daemon PID - (as returned by <code class="function">getpid()</code>) to a PID file, - for example <code class="filename">/run/foobar.pid</code> (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.</p></li><li class="listitem"><p>In the daemon process, drop privileges, if - possible and applicable.</p></li><li class="listitem"><p>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 - <code class="function">fork()</code> and hence available in both the - original and the daemon process.</p></li><li class="listitem"><p>Call <code class="function">exit()</code> in the - original process. The process that invoked the daemon must be - able to rely on that this <code class="function">exit()</code> happens - after initialization is complete and all external - communication channels are established and - accessible.</p></li></ol></div><p>The BSD <code class="function">daemon()</code> function should not - be used, as it implements only a subset of these steps.</p><p>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.</p></div><div class="refsect2"><a name="idm47144709519616"></a><h3 id="New-Style Daemons">New-Style Daemons<a class="headerlink" title="Permalink to this headline" href="#New-Style%20Daemons">¶</a></h3><p>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.</p><p>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.</p><p>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 - <code class="filename">/dev/null</code> unless otherwise configured. The - umask is reset. - </p><p>It is recommended for new-style daemons to implement the - following:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>If <code class="constant">SIGTERM</code> is received, - shut down the daemon and exit cleanly.</p></li><li class="listitem"><p>If <code class="constant">SIGHUP</code> is received, - reload the configuration files, if this - applies.</p></li><li class="listitem"><p>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 <a class="ulink" href="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html" target="_top">LSB - recommendations for SysV init - scripts</a>.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>For integration in systemd, provide a - <code class="filename">.service</code> unit file that carries - information about starting, stopping and otherwise maintaining - the daemon. See - <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a> - for details.</p></li><li class="listitem"><p>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 - <a href="systemd.exec.html"><span class="citerefentry"><span class="refentrytitle">systemd.exec</span>(5)</span></a> - for the available controls.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>If applicable, a daemon should notify the init - system about startup completion or status updates via the - <a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a> - interface.</p></li><li class="listitem"><p>Instead of using the - <code class="function">syslog()</code> call to log directly to the - system syslog service, a new-style daemon may choose to simply - log to standard error via <code class="function">fprintf()</code>, - 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 - "<code class="literal"><4></code>" (for log level 4 "WARNING" in the - syslog priority scheme), following a similar style as the - Linux kernel's <code class="function">printk()</code> level system. For - details, see - <a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a> - and - <a href="systemd.exec.html"><span class="citerefentry"><span class="refentrytitle">systemd.exec</span>(5)</span></a>.</p></li></ol></div><p>These recommendations are similar but not identical to the - <a class="ulink" href="https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html" target="_top">Apple - MacOS X Daemon Requirements</a>.</p></div></div><div class="refsect1"><a name="idm47144709496560"></a><h2 id="Activation">Activation<a class="headerlink" title="Permalink to this headline" href="#Activation">¶</a></h2><p>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: - <code class="filename">bluetoothd.service</code> 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.</p><div class="refsect2"><a name="idm47144709493632"></a><h3 id="Activation on Boot">Activation on Boot<a class="headerlink" title="Permalink to this headline" href="#Activation%20on%20Boot">¶</a></h3><p>Old-style daemons are usually activated exclusively on - boot (and manually by the administrator) via SysV init scripts, - as detailed in the <a class="ulink" href="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html" target="_top">LSB - Linux Standard Base Core Specification</a>. 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.</p><p>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 <code class="filename">.wants/</code> directory of - either <code class="filename">multi-user.target</code> or - <code class="filename">graphical.target</code>, which are normally used - as boot targets at system startup. See - <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a> - for details about the <code class="filename">.wants/</code> directories, - and - <a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a> - for details about the two boot targets.</p></div><div class="refsect2"><a name="idm47144709486416"></a><h3 id="Socket-Based Activation">Socket-Based Activation<a class="headerlink" title="Permalink to this headline" href="#Socket-Based%20Activation">¶</a></h3><p>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.</p><p>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 - <a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a> - and - <a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>. - 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.</p><p>systemd implements socket-based activation via - <code class="filename">.socket</code> units, which are described in - <a href="systemd.socket.html"><span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span></a>. - When configuring socket units for socket-based activation, it is - essential that all listening sockets are pulled in by the - special target unit <code class="filename">sockets.target</code>. It is - recommended to place a - <code class="varname">WantedBy=sockets.target</code> directive in the - "<code class="literal">[Install]</code>" section to automatically add such a - dependency on installation of a socket unit. Unless - <code class="varname">DefaultDependencies=no</code> is set, the necessary - ordering dependencies are implicitly created for all socket - units. For more information about - <code class="filename">sockets.target</code>, see - <a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a>. - It is not necessary or recommended to place any additional - dependencies on socket units (for example from - <code class="filename">multi-user.target</code> or suchlike) when one is - installed in <code class="filename">sockets.target</code>.</p></div><div class="refsect2"><a name="idm47144709474240"></a><h3 id="Bus-Based Activation">Bus-Based Activation<a class="headerlink" title="Permalink to this headline" href="#Bus-Based%20Activation">¶</a></h3><p>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 <code class="varname">SystemdService=</code> - 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 - <code class="filename">org.freedesktop.RealtimeKit.service</code>, make - sure to set - <code class="varname">SystemdService=rtkit-daemon.service</code> in that - file to bind it to the systemd service - <code class="filename">rtkit-daemon.service</code>. This is needed to - make sure that the daemon is started in a race-free fashion when - activated via multiple mechanisms simultaneously.</p></div><div class="refsect2"><a name="idm47144714511600"></a><h3 id="Device-Based Activation">Device-Based Activation<a class="headerlink" title="Permalink to this headline" href="#Device-Based%20Activation">¶</a></h3><p>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 "<code class="literal">systemd</code>". - 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 <code class="varname">SYSTEMD_WANTS=</code> property. See - <a href="systemd.device.html"><span class="citerefentry"><span class="refentrytitle">systemd.device</span>(5)</span></a> - for details. Often, it is nicer to pull in services from devices - only indirectly via dedicated targets. Example: Instead of - pulling in <code class="filename">bluetoothd.service</code> from all the - various bluetooth dongles and other hardware available, pull in - bluetooth.target from them and - <code class="filename">bluetoothd.service</code> from that target. This - provides for nicer abstraction and gives administrators the - option to enable <code class="filename">bluetoothd.service</code> via - controlling a <code class="filename">bluetooth.target.wants/</code> - symlink uniformly with a command like <span class="command"><strong>enable</strong></span> - of - <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a> - instead of manipulating the udev ruleset.</p></div><div class="refsect2"><a name="idm47144709453360"></a><h3 id="Path-Based Activation">Path-Based Activation<a class="headerlink" title="Permalink to this headline" href="#Path-Based%20Activation">¶</a></h3><p>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 <code class="filename">.path</code> - units, as outlined in - <a href="systemd.path.html"><span class="citerefentry"><span class="refentrytitle">systemd.path</span>(5)</span></a>.</p></div><div class="refsect2"><a name="idm47144709450432"></a><h3 id="Timer-Based Activation">Timer-Based Activation<a class="headerlink" title="Permalink to this headline" href="#Timer-Based%20Activation">¶</a></h3><p>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 - <code class="filename">.timer</code> units, as described in - <a href="systemd.timer.html"><span class="citerefentry"><span class="refentrytitle">systemd.timer</span>(5)</span></a>.</p></div><div class="refsect2"><a name="idm47144709447680"></a><h3 id="Other Forms of Activation">Other Forms of Activation<a class="headerlink" title="Permalink to this headline" href="#Other%20Forms%20of%20Activation">¶</a></h3><p>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 <code class="filename">.socket</code> 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 - <code class="constant">IP_FREEBIND</code> socket option, as accessible - via <code class="varname">FreeBind=yes</code> in systemd socket files (see - <a href="systemd.socket.html"><span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span></a> - 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 - <code class="varname">CPUSchedulingPolicy=idle</code> and/or - <code class="varname">IOSchedulingClass=idle</code>. 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.</p></div></div><div class="refsect1"><a name="idm47144709441696"></a><h2 id="Integration with Systemd">Integration with Systemd<a class="headerlink" title="Permalink to this headline" href="#Integration%20with%20Systemd">¶</a></h2><div class="refsect2"><a name="idm47144709441056"></a><h3 id="Writing Systemd Unit Files">Writing Systemd Unit Files<a class="headerlink" title="Permalink to this headline" href="#Writing%20Systemd%20Unit%20Files">¶</a></h3><p>When writing systemd unit files, it is recommended to - consider the following suggestions:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>If possible, do not use the - <code class="varname">Type=forking</code> setting in service files. But - if you do, make sure to set the PID file path using - <code class="varname">PIDFile=</code>. See - <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a> - for details.</p></li><li class="listitem"><p>If your daemon registers a D-Bus name on the - bus, make sure to use <code class="varname">Type=dbus</code> in the - service file if possible.</p></li><li class="listitem"><p>Make sure to set a good human-readable - description string with - <code class="varname">Description=</code>.</p></li><li class="listitem"><p>Do not disable - <code class="varname">DefaultDependencies=</code>, unless you really - know what you do and your unit is involved in early boot or - late system shutdown.</p></li><li class="listitem"><p>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 - <a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a> - or names introduced by your own package to keep the unit file - operating system-independent.</p></li><li class="listitem"><p>Make sure to include an - "<code class="literal">[Install]</code>" section including installation - information for the unit file. See - <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a> - for details. To activate your service on boot, make sure to - add a <code class="varname">WantedBy=multi-user.target</code> or - <code class="varname">WantedBy=graphical.target</code> directive. To - activate your socket on boot, make sure to add - <code class="varname">WantedBy=sockets.target</code>. Usually, you also - want to make sure that when your service is installed, your - socket is installed too, hence add - <code class="varname">Also=foo.socket</code> in your service file - <code class="filename">foo.service</code>, for a hypothetical program - <code class="filename">foo</code>.</p></li></ol></div></div><div class="refsect2"><a name="idm47144709427104"></a><h3 id="Installing Systemd Service Files">Installing Systemd Service Files<a class="headerlink" title="Permalink to this headline" href="#Installing%20Systemd%20Service%20Files">¶</a></h3><p>At the build installation time (e.g. <span class="command"><strong>make - install</strong></span> during package build), packages are - recommended to install their systemd unit files in the directory - returned by <span class="command"><strong>pkg-config systemd - --variable=systemdsystemunitdir</strong></span> (for system services) - or <span class="command"><strong>pkg-config systemd - --variable=systemduserunitdir</strong></span> (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. <span class="command"><strong>rpm - -i</strong></span> by the administrator), symlinks should be created - in the systemd configuration directories via the - <span class="command"><strong>enable</strong></span> command of the - <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a> - tool to activate them automatically on boot.</p><p>Packages using - <a href="http://linux.die.net/man/1/autoconf"><span class="citerefentry"><span class="refentrytitle">autoconf</span>(1)</span></a> - are recommended to use a configure script - excerpt like the following to determine the - unit installation path during source - configuration:</p><pre class="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"])</pre><p>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.)</p><p>Additionally, to ensure that - <span class="command"><strong>make distcheck</strong></span> continues to - work, it is recommended to add the following - to the top-level <code class="filename">Makefile.am</code> - file in - <a href="http://linux.die.net/man/1/automake"><span class="citerefentry"><span class="refentrytitle">automake</span>(1)</span></a>-based - projects:</p><pre class="programlisting">DISTCHECK_CONFIGURE_FLAGS = \ - --with-systemdsystemunitdir=$$dc_install_base/$(systemdsystemunitdir)</pre><p>Finally, unit files should be installed in the system with an automake excerpt like the following:</p><pre class="programlisting">if HAVE_SYSTEMD -systemdsystemunit_DATA = \ - foobar.socket \ - foobar.service -endif</pre><p>In the - <a href="http://linux.die.net/man/8/rpm"><span class="citerefentry"><span class="refentrytitle">rpm</span>(8)</span></a> - <code class="filename">.spec</code> 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.</p><p>At the top of the file:</p><pre class="programlisting">BuildRequires: systemd -%{?systemd_requires}</pre><p>And as scriptlets, further down:</p><pre class="programlisting">%post -%systemd_post foobar.service foobar.socket - -%preun -%systemd_preun foobar.service foobar.socket - -%postun -%systemd_postun</pre><p>If the service shall be restarted during upgrades, replace - the "<code class="literal">%postun</code>" scriptlet above with the - following:</p><pre class="programlisting">%postun -%systemd_postun_with_restart foobar.service</pre><p>Note that "<code class="literal">%systemd_post</code>" and - "<code class="literal">%systemd_preun</code>" expect the names of all units - that are installed/removed as arguments, separated by spaces. - "<code class="literal">%systemd_postun</code>" expects no arguments. - "<code class="literal">%systemd_postun_with_restart</code>" expects the - units to restart as arguments.</p><p>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:</p><pre class="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</pre><p>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 - <span class="command"><strong>chkconfig</strong></span> 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.</p></div></div><div class="refsect1"><a name="idm47144709400512"></a><h2 id="Porting Existing Daemons">Porting Existing Daemons<a class="headerlink" title="Permalink to this headline" href="#Porting%20Existing%20Daemons">¶</a></h2><p>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.</p><p>To port an existing SysV compatible daemon, the following - steps are recommended:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>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.</p></li><li class="listitem"><p>If the daemon offers interfaces to other - software running on the local system via local - <code class="constant">AF_UNIX</code> 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 - <a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a> - is checked for already passed sockets first. If sockets are - passed (i.e. when <code class="function">sd_listen_fds()</code> returns a - positive value), skip the socket creation step and use the - passed sockets. Secondly, ensure that the file system socket - nodes for local <code class="constant">AF_UNIX</code> 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.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>If the daemon exposes interfaces via D-Bus, - write and install a D-Bus activation file for the service, see - above for details.</p></li></ol></div></div><div class="refsect1"><a name="idm47144709391648"></a><h2 id="Placing Daemon Data">Placing Daemon Data<a class="headerlink" title="Permalink to this headline" href="#Placing%20Daemon%20Data">¶</a></h2><p>It is recommended to follow the general guidelines for - placing package files, as discussed in - <a href="file-hierarchy.html"><span class="citerefentry"><span class="refentrytitle">file-hierarchy</span>(7)</span></a>.</p></div><div class="refsect1"><a name="idm47144709389616"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p> - <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, - <a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>, - <a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a>, - <a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>, - <a href="daemon.html"><span class="citerefentry"><span class="refentrytitle">daemon</span>(3)</span></a>, - <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>, - <a href="file-hierarchy.html"><span class="citerefentry"><span class="refentrytitle">file-hierarchy</span>(7)</span></a> - </p></div></div></body></html> |