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8dd4c05b | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
f9378423 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2010 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
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11 | under the terms of the GNU Lesser General Public License as published by |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
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13 | (at your option) any later version. |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 18 | Lesser General Public License for more details. |
f9378423 | 19 | |
5430f7f2 | 20 | You should have received a copy of the GNU Lesser General Public License |
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21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
22 | --> | |
23 | ||
6a70f3aa | 24 | <refentry id="sd_notify" |
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25 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
26 | ||
27 | <refentryinfo> | |
28 | <title>sd_notify</title> | |
29 | <productname>systemd</productname> | |
30 | ||
31 | <authorgroup> | |
32 | <author> | |
33 | <contrib>Developer</contrib> | |
34 | <firstname>Lennart</firstname> | |
35 | <surname>Poettering</surname> | |
36 | <email>lennart@poettering.net</email> | |
37 | </author> | |
38 | </authorgroup> | |
39 | </refentryinfo> | |
40 | ||
41 | <refmeta> | |
42 | <refentrytitle>sd_notify</refentrytitle> | |
43 | <manvolnum>3</manvolnum> | |
44 | </refmeta> | |
45 | ||
46 | <refnamediv> | |
47 | <refname>sd_notify</refname> | |
48 | <refname>sd_notifyf</refname> | |
49 | <refname>sd_pid_notify</refname> | |
50 | <refname>sd_pid_notifyf</refname> | |
51 | <refname>sd_pid_notify_with_fds</refname> | |
52 | <refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose> | |
53 | </refnamediv> | |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
58 | ||
59 | <funcprototype> | |
60 | <funcdef>int <function>sd_notify</function></funcdef> | |
61 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
62 | <paramdef>const char *<parameter>state</parameter></paramdef> | |
63 | </funcprototype> | |
64 | ||
65 | <funcprototype> | |
66 | <funcdef>int <function>sd_notifyf</function></funcdef> | |
67 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
68 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 69 | <paramdef>…</paramdef> |
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70 | </funcprototype> |
71 | ||
72 | <funcprototype> | |
73 | <funcdef>int <function>sd_pid_notify</function></funcdef> | |
74 | <paramdef>pid_t <parameter>pid</parameter></paramdef> | |
75 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
76 | <paramdef>const char *<parameter>state</parameter></paramdef> | |
77 | </funcprototype> | |
78 | ||
79 | <funcprototype> | |
80 | <funcdef>int <function>sd_pid_notifyf</function></funcdef> | |
81 | <paramdef>pid_t <parameter>pid</parameter></paramdef> | |
82 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
83 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 84 | <paramdef>…</paramdef> |
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85 | </funcprototype> |
86 | ||
87 | <funcprototype> | |
88 | <funcdef>int <function>sd_pid_notify_with_fds</function></funcdef> | |
89 | <paramdef>pid_t <parameter>pid</parameter></paramdef> | |
90 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
91 | <paramdef>const char *<parameter>state</parameter></paramdef> | |
92 | <paramdef>const int *<parameter>fds</parameter></paramdef> | |
93 | <paramdef>unsigned <parameter>n_fds</parameter></paramdef> | |
94 | </funcprototype> | |
95 | </funcsynopsis> | |
96 | </refsynopsisdiv> | |
97 | ||
98 | <refsect1> | |
99 | <title>Description</title> | |
100 | <para><function>sd_notify()</function> may be called by a service | |
101 | to notify the service manager about state changes. It can be used | |
102 | to send arbitrary information, encoded in an | |
b938cb90 | 103 | environment-block-like string. Most importantly, it can be used for |
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104 | start-up completion notification.</para> |
105 | ||
106 | <para>If the <parameter>unset_environment</parameter> parameter is | |
107 | non-zero, <function>sd_notify()</function> will unset the | |
108 | <varname>$NOTIFY_SOCKET</varname> environment variable before | |
109 | returning (regardless of whether the function call itself | |
110 | succeeded or not). Further calls to | |
111 | <function>sd_notify()</function> will then fail, but the variable | |
112 | is no longer inherited by child processes.</para> | |
113 | ||
114 | <para>The <parameter>state</parameter> parameter should contain a | |
115 | newline-separated list of variable assignments, similar in style | |
116 | to an environment block. A trailing newline is implied if none is | |
117 | specified. The string may contain any kind of variable | |
118 | assignments, but the following shall be considered | |
119 | well-known:</para> | |
120 | ||
121 | <variablelist> | |
122 | <varlistentry> | |
123 | <term>READY=1</term> | |
124 | ||
125 | <listitem><para>Tells the service manager that service startup | |
126 | is finished. This is only used by systemd if the service | |
127 | definition file has Type=notify set. Since there is little | |
128 | value in signaling non-readiness, the only value services | |
129 | should send is <literal>READY=1</literal> (i.e. | |
130 | <literal>READY=0</literal> is not defined).</para></listitem> | |
131 | </varlistentry> | |
132 | ||
133 | <varlistentry> | |
134 | <term>RELOADING=1</term> | |
135 | ||
136 | <listitem><para>Tells the service manager that the service is | |
137 | reloading its configuration. This is useful to allow the | |
138 | service manager to track the service's internal state, and | |
139 | present it to the user. Note that a service that sends this | |
140 | notification must also send a <literal>READY=1</literal> | |
141 | notification when it completed reloading its | |
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142 | configuration. Reloads are propagated in the same way as they |
143 | are when initiated by the user.</para></listitem> | |
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144 | </varlistentry> |
145 | ||
146 | <varlistentry> | |
147 | <term>STOPPING=1</term> | |
148 | ||
149 | <listitem><para>Tells the service manager that the service is | |
150 | beginning its shutdown. This is useful to allow the service | |
151 | manager to track the service's internal state, and present it | |
152 | to the user.</para></listitem> | |
153 | </varlistentry> | |
154 | ||
155 | <varlistentry> | |
1eecafb8 | 156 | <term>STATUS=…</term> |
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157 | |
158 | <listitem><para>Passes a single-line UTF-8 status string back | |
159 | to the service manager that describes the service state. This | |
160 | is free-form and can be used for various purposes: general | |
161 | state feedback, fsck-like programs could pass completion | |
b938cb90 | 162 | percentages and failing programs could pass a human-readable |
798d3a52 | 163 | error message. Example: <literal>STATUS=Completed 66% of file |
1eecafb8 | 164 | system check…</literal></para></listitem> |
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165 | </varlistentry> |
166 | ||
167 | <varlistentry> | |
1eecafb8 | 168 | <term>ERRNO=…</term> |
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169 | |
170 | <listitem><para>If a service fails, the errno-style error | |
171 | code, formatted as string. Example: <literal>ERRNO=2</literal> | |
172 | for ENOENT.</para></listitem> | |
173 | </varlistentry> | |
174 | ||
175 | <varlistentry> | |
1eecafb8 | 176 | <term>BUSERROR=…</term> |
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177 | |
178 | <listitem><para>If a service fails, the D-Bus error-style | |
179 | error code. Example: | |
180 | <literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem> | |
181 | </varlistentry> | |
182 | ||
183 | <varlistentry> | |
1eecafb8 | 184 | <term>MAINPID=…</term> |
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185 | |
186 | <listitem><para>The main process ID (PID) of the service, in | |
187 | case the service manager did not fork off the process itself. | |
188 | Example: <literal>MAINPID=4711</literal></para></listitem> | |
189 | </varlistentry> | |
190 | ||
191 | <varlistentry> | |
192 | <term>WATCHDOG=1</term> | |
193 | ||
194 | <listitem><para>Tells the service manager to update the | |
195 | watchdog timestamp. This is the keep-alive ping that services | |
196 | need to issue in regular intervals if | |
197 | <varname>WatchdogSec=</varname> is enabled for it. See | |
198 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
199 | for information how to enable this functionality and | |
200 | <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
1d3eaa93 | 201 | for the details of how the service can check whether the |
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202 | watchdog is enabled. </para></listitem> |
203 | </varlistentry> | |
204 | ||
205 | ||
206 | <varlistentry> | |
207 | <term>FDSTORE=1</term> | |
208 | ||
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209 | <listitem><para>Stores additional file descriptors in the service manager. File descriptors sent this way will |
210 | be maintained per-service by the service manager and will later be handed back using the usual file descriptor | |
211 | passing logic at the next invocation of the service, see | |
212 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This is | |
213 | useful for implementing services that can restart after an explicit request or a crash without losing | |
214 | state. Any open sockets and other file descriptors which should not be closed during the restart may be stored | |
215 | this way. Application state can either be serialized to a file in <filename>/run</filename>, or better, stored | |
216 | in a <citerefentry><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> memory | |
217 | file descriptor. Note that the service manager will accept messages for a service only if its | |
218 | <varname>FileDescriptorStoreMax=</varname> setting is non-zero (defaults to zero, see | |
219 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>). If file | |
220 | descriptors sent are pollable (see | |
221 | <citerefentry><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), then any | |
222 | <constant>EPOLLHUP</constant> or <constant>EPOLLERR</constant> event seen on them will result in their | |
223 | automatic removal from the store. Multiple arrays of file descriptors may be sent in separate messages, in | |
224 | which case the arrays are combined. Note that the service manager removes duplicate (pointing to the same | |
225 | object) file descriptors before passing them to the service. Use <function>sd_pid_notify_with_fds()</function> | |
226 | to send messages with <literal>FDSTORE=1</literal>, see below.</para></listitem> | |
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227 | </varlistentry> |
228 | ||
8dd4c05b | 229 | <varlistentry> |
1eecafb8 | 230 | <term>FDNAME=…</term> |
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231 | |
232 | <listitem><para>When used in combination with | |
b938cb90 | 233 | <varname>FDSTORE=1</varname>, specifies a name for the |
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234 | submitted file descriptors. This name is passed to the service |
235 | during activation, and may be queried using | |
236 | <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>. File | |
237 | descriptors submitted without this field set, will implicitly | |
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238 | get the name <literal>stored</literal> assigned. Note that, if |
239 | multiple file descriptors are submitted at once, the specified | |
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240 | name will be assigned to all of them. In order to assign |
241 | different names to submitted file descriptors, submit them in | |
7f3fdb7f | 242 | separate invocations of |
8dd4c05b | 243 | <function>sd_pid_notify_with_fds()</function>. The name may |
a8eaaee7 | 244 | consist of any ASCII character, but must not contain control |
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245 | characters or <literal>:</literal>. It may not be longer than |
246 | 255 characters. If a submitted name does not follow these | |
b938cb90 | 247 | restrictions, it is ignored.</para></listitem> |
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248 | </varlistentry> |
249 | ||
2787d83c | 250 | <varlistentry> |
1eecafb8 | 251 | <term>WATCHDOG_USEC=…</term> |
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252 | |
253 | <listitem><para>Reset <varname>watchdog_usec</varname> value during runtime. | |
254 | Notice that this is not available when using <function>sd_event_set_watchdog()</function> | |
255 | or <function>sd_watchdog_enabled()</function>. | |
256 | Example : <literal>WATCHDOG_USEC=20000000</literal></para></listitem> | |
257 | </varlistentry> | |
258 | ||
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259 | </variablelist> |
260 | ||
261 | <para>It is recommended to prefix variable names that are not | |
262 | listed above with <varname>X_</varname> to avoid namespace | |
263 | clashes.</para> | |
264 | ||
265 | <para>Note that systemd will accept status data sent from a | |
266 | service only if the <varname>NotifyAccess=</varname> option is | |
267 | correctly set in the service definition file. See | |
268 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
269 | for details.</para> | |
270 | ||
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271 | <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either |
272 | the sending process is still around at the time PID 1 processes the message, or if the sending process is | |
273 | explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked | |
274 | off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or | |
275 | <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an | |
276 | <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly | |
277 | attribute the message to the unit, and thus will ignore it, even if | |
278 | <varname>NotifyAccess=</varname><option>all</option> is set for it.</para> | |
279 | ||
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280 | <para><function>sd_notifyf()</function> is similar to |
281 | <function>sd_notify()</function> but takes a | |
282 | <function>printf()</function>-like format string plus | |
283 | arguments.</para> | |
284 | ||
285 | <para><function>sd_pid_notify()</function> and | |
286 | <function>sd_pid_notifyf()</function> are similar to | |
287 | <function>sd_notify()</function> and | |
288 | <function>sd_notifyf()</function> but take a process ID (PID) to | |
289 | use as originating PID for the message as first argument. This is | |
290 | useful to send notification messages on behalf of other processes, | |
291 | provided the appropriate privileges are available. If the PID | |
b938cb90 | 292 | argument is specified as 0, the process ID of the calling process |
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293 | is used, in which case the calls are fully equivalent to |
294 | <function>sd_notify()</function> and | |
295 | <function>sd_notifyf()</function>.</para> | |
296 | ||
297 | <para><function>sd_pid_notify_with_fds()</function> is similar to | |
298 | <function>sd_pid_notify()</function> but takes an additional array | |
299 | of file descriptors. These file descriptors are sent along the | |
300 | notification message to the service manager. This is particularly | |
301 | useful for sending <literal>FDSTORE=1</literal> messages, as | |
302 | described above. The additional arguments are a pointer to the | |
303 | file descriptor array plus the number of file descriptors in the | |
304 | array. If the number of file descriptors is passed as 0, the call | |
305 | is fully equivalent to <function>sd_pid_notify()</function>, i.e. | |
306 | no file descriptors are passed. Note that sending file descriptors | |
307 | to the service manager on messages that do not expect them (i.e. | |
308 | without <literal>FDSTORE=1</literal>) they are immediately closed | |
309 | on reception.</para> | |
310 | </refsect1> | |
311 | ||
312 | <refsect1> | |
313 | <title>Return Value</title> | |
314 | ||
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315 | <para>On failure, these calls return a negative errno-style error code. If <varname>$NOTIFY_SOCKET</varname> was |
316 | not set and hence no status message could be sent, 0 is returned. If the status was sent, these functions return a | |
317 | positive value. In order to support both service managers that implement this scheme and those which do not, it is | |
318 | generally recommended to ignore the return value of this call. Note that the return value simply indicates whether | |
319 | the notification message was enqueued properly, it does not reflect whether the message could be processed | |
320 | successfully. Specifically, no error is returned when a file descriptor is attempted to be stored using | |
321 | <varname>FDSTORE=1</varname> but the service is not actually configured to permit storing of file descriptors (see | |
322 | above).</para> | |
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323 | </refsect1> |
324 | ||
325 | <refsect1> | |
326 | <title>Notes</title> | |
327 | ||
328 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
329 | ||
3122633a | 330 | <para>These functions send a single datagram with the |
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331 | state string as payload to the <constant>AF_UNIX</constant> socket |
332 | referenced in the <varname>$NOTIFY_SOCKET</varname> environment | |
333 | variable. If the first character of | |
334 | <varname>$NOTIFY_SOCKET</varname> is <literal>@</literal>, the | |
335 | string is understood as Linux abstract namespace socket. The | |
336 | datagram is accompanied by the process credentials of the sending | |
337 | service, using SCM_CREDENTIALS.</para> | |
338 | </refsect1> | |
339 | ||
340 | <refsect1> | |
341 | <title>Environment</title> | |
342 | ||
343 | <variablelist class='environment-variables'> | |
344 | <varlistentry> | |
345 | <term><varname>$NOTIFY_SOCKET</varname></term> | |
346 | ||
347 | <listitem><para>Set by the service manager for supervised | |
348 | processes for status and start-up completion notification. | |
349 | This environment variable specifies the socket | |
350 | <function>sd_notify()</function> talks to. See above for | |
351 | details.</para></listitem> | |
352 | </varlistentry> | |
353 | </variablelist> | |
354 | </refsect1> | |
355 | ||
356 | <refsect1> | |
357 | <title>Examples</title> | |
358 | ||
359 | <example> | |
360 | <title>Start-up Notification</title> | |
361 | ||
362 | <para>When a service finished starting up, it might issue the | |
363 | following call to notify the service manager:</para> | |
364 | ||
365 | <programlisting>sd_notify(0, "READY=1");</programlisting> | |
366 | </example> | |
367 | ||
368 | <example> | |
369 | <title>Extended Start-up Notification</title> | |
370 | ||
371 | <para>A service could send the following after completing | |
372 | initialization:</para> | |
373 | ||
374 | <programlisting>sd_notifyf(0, "READY=1\n" | |
1eecafb8 | 375 | "STATUS=Processing requests…\n" |
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376 | "MAINPID=%lu", |
377 | (unsigned long) getpid());</programlisting> | |
378 | </example> | |
379 | ||
380 | <example> | |
381 | <title>Error Cause Notification</title> | |
382 | ||
383 | <para>A service could send the following shortly before exiting, on failure:</para> | |
384 | ||
385 | <programlisting>sd_notifyf(0, "STATUS=Failed to start up: %s\n" | |
386 | "ERRNO=%i", | |
387 | strerror(errno), | |
388 | errno);</programlisting> | |
389 | </example> | |
390 | ||
391 | <example> | |
392 | <title>Store a File Descriptor in the Service Manager</title> | |
393 | ||
394 | <para>To store an open file descriptor in the service manager, | |
395 | in order to continue operation after a service restart without | |
b938cb90 | 396 | losing state, use <literal>FDSTORE=1</literal>:</para> |
798d3a52 | 397 | |
8dd4c05b | 398 | <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", &fd, 1);</programlisting> |
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399 | </example> |
400 | </refsect1> | |
401 | ||
402 | <refsect1> | |
403 | <title>See Also</title> | |
404 | <para> | |
405 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
406 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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407 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
408 | <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
409 | <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
798d3a52 | 410 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
8dd4c05b | 411 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
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412 | </para> |
413 | </refsect1> | |
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414 | |
415 | </refentry> |