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1f812fea | 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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="systemd.socket"> | |
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10 | <refentryinfo> |
11 | <title>systemd.socket</title> | |
12 | <productname>systemd</productname> | |
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13 | </refentryinfo> |
14 | ||
15 | <refmeta> | |
16 | <refentrytitle>systemd.socket</refentrytitle> | |
17 | <manvolnum>5</manvolnum> | |
18 | </refmeta> | |
19 | ||
20 | <refnamediv> | |
21 | <refname>systemd.socket</refname> | |
22 | <refpurpose>Socket unit configuration</refpurpose> | |
23 | </refnamediv> | |
24 | ||
25 | <refsynopsisdiv> | |
26 | <para><filename><replaceable>socket</replaceable>.socket</filename></para> | |
27 | </refsynopsisdiv> | |
28 | ||
29 | <refsect1> | |
30 | <title>Description</title> | |
31 | ||
32 | <para>A unit configuration file whose name ends in | |
33 | <literal>.socket</literal> encodes information about an IPC or | |
34 | network socket or a file system FIFO controlled and supervised by | |
35 | systemd, for socket-based activation.</para> | |
36 | ||
37 | <para>This man page lists the configuration options specific to | |
38 | this unit type. See | |
39 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
40 | for the common options of all unit configuration files. The common | |
41 | configuration items are configured in the generic [Unit] and | |
42 | [Install] sections. The socket specific configuration options are | |
43 | configured in the [Socket] section.</para> | |
44 | ||
45 | <para>Additional options are listed in | |
46 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
47 | which define the execution environment the | |
48 | <option>ExecStartPre=</option>, <option>ExecStartPost=</option>, | |
49 | <option>ExecStopPre=</option> and <option>ExecStopPost=</option> | |
50 | commands are executed in, and in | |
51 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
52 | which define the way the processes are terminated, and in | |
53 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
54 | which configure resource control settings for the processes of the | |
55 | socket.</para> | |
56 | ||
57 | <para>For each socket file, a matching service file must exist, | |
58 | describing the service to start on incoming traffic on the socket | |
59 | (see | |
60 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
61 | for more information about .service files). The name of the | |
62 | .service unit is by default the same as the name of the .socket | |
63 | unit, but can be altered with the <option>Service=</option> option | |
64 | described below. Depending on the setting of the | |
65 | <option>Accept=</option> option described below, this .service | |
66 | unit must either be named like the .socket unit, but with the | |
67 | suffix replaced, unless overridden with <option>Service=</option>; | |
68 | or it must be a template unit named the same way. Example: a | |
69 | socket file <filename>foo.socket</filename> needs a matching | |
70 | service <filename>foo.service</filename> if | |
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71 | <option>Accept=no</option> is set. If |
72 | <option>Accept=yes</option> is set, a service template file | |
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73 | <filename>foo@.service</filename> must exist from which services |
74 | are instantiated for each incoming connection.</para> | |
75 | ||
45f09f93 | 76 | <para>No implicit <varname>WantedBy=</varname> or |
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77 | <varname>RequiredBy=</varname> dependency from the socket to the |
78 | service is added. This means that the service may be started | |
79 | without the socket, in which case it must be able to open sockets | |
80 | by itself. To prevent this, an explicit | |
81 | <varname>Requires=</varname> dependency may be added.</para> | |
82 | ||
83 | <para>Socket units may be used to implement on-demand starting of | |
84 | services, as well as parallelized starting of services. See the | |
85 | blog stories linked at the end for an introduction.</para> | |
86 | ||
87 | <para>Note that the daemon software configured for socket | |
88 | activation with socket units needs to be able to accept sockets | |
89 | from systemd, either via systemd's native socket passing interface | |
90 | (see | |
91 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
92 | for details) or via the traditional | |
b5c7d097 | 93 | <citerefentry project='freebsd'><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>-style |
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94 | socket passing (i.e. sockets passed in via standard input and |
95 | output, using <varname>StandardInput=socket</varname> in the | |
96 | service file).</para> | |
97 | </refsect1> | |
98 | ||
c129bd5d | 99 | <refsect1> |
aed5cb03 ZJS |
100 | <title>Automatic Dependencies</title> |
101 | ||
102 | <refsect2> | |
103 | <title>Implicit Dependencies</title> | |
104 | ||
105 | <para>The following dependencies are implicitly added:</para> | |
106 | ||
107 | <itemizedlist> | |
108 | <listitem><para>Socket units automatically gain a <varname>Before=</varname> | |
109 | dependency on the service units they activate.</para></listitem> | |
110 | ||
111 | <listitem><para>Socket units referring to file system paths (such as AF_UNIX | |
112 | sockets or FIFOs) implicitly gain <varname>Requires=</varname> and | |
113 | <varname>After=</varname> dependencies on all mount units | |
114 | necessary to access those paths.</para></listitem> | |
115 | ||
116 | <listitem><para>Socket units using the <varname>BindToDevice=</varname> | |
117 | setting automatically gain a <varname>BindsTo=</varname> and | |
118 | <varname>After=</varname> dependency on the device unit | |
119 | encapsulating the specified network interface.</para></listitem> | |
120 | </itemizedlist> | |
121 | ||
122 | <para>Additional implicit dependencies may be added as result of | |
123 | execution and resource control parameters as documented in | |
124 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
125 | and | |
126 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> | |
127 | </refsect2> | |
128 | ||
129 | <refsect2> | |
130 | <title>Default Dependencies</title> | |
131 | ||
132 | <para>The following dependencies are added unless | |
133 | <varname>DefaultDependencies=no</varname> is set:</para> | |
134 | ||
135 | <itemizedlist> | |
136 | <listitem><para>Socket units automatically gain a | |
137 | <varname>Before=</varname> dependency on | |
138 | <filename>sockets.target</filename>.</para></listitem> | |
139 | ||
140 | <listitem><para>Socket units automatically gain a pair of | |
141 | <varname>After=</varname> and <varname>Requires=</varname> | |
142 | dependency on <filename>sysinit.target</filename>, and a pair of | |
143 | <varname>Before=</varname> and <varname>Conflicts=</varname> | |
144 | dependencies on <filename>shutdown.target</filename>. These | |
145 | dependencies ensure that the socket unit is started before normal | |
146 | services at boot, and is stopped on shutdown. Only sockets | |
147 | involved with early boot or late system shutdown should disable | |
148 | <varname>DefaultDependencies=</varname> option.</para></listitem> | |
149 | </itemizedlist> | |
150 | </refsect2> | |
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151 | </refsect1> |
152 | ||
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153 | <refsect1> |
154 | <title>Options</title> | |
155 | ||
156 | <para>Socket files must include a [Socket] section, which carries | |
157 | information about the socket or FIFO it supervises. A number of | |
158 | options that may be used in this section are shared with other | |
159 | unit types. These options are documented in | |
160 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
161 | and | |
162 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
163 | The options specific to the [Socket] section of socket units are | |
164 | the following:</para> | |
165 | ||
166 | <variablelist class='unit-directives'> | |
167 | <varlistentry> | |
168 | <term><varname>ListenStream=</varname></term> | |
169 | <term><varname>ListenDatagram=</varname></term> | |
170 | <term><varname>ListenSequentialPacket=</varname></term> | |
171 | <listitem><para>Specifies an address to listen on for a stream | |
172 | (<constant>SOCK_STREAM</constant>), datagram | |
173 | (<constant>SOCK_DGRAM</constant>), or sequential packet | |
174 | (<constant>SOCK_SEQPACKET</constant>) socket, respectively. | |
175 | The address can be written in various formats:</para> | |
176 | ||
177 | <para>If the address starts with a slash | |
178 | (<literal>/</literal>), it is read as file system socket in | |
179 | the <constant>AF_UNIX</constant> socket family.</para> | |
180 | ||
181 | <para>If the address starts with an at symbol | |
182 | (<literal>@</literal>), it is read as abstract namespace | |
183 | socket in the <constant>AF_UNIX</constant> family. The | |
184 | <literal>@</literal> is replaced with a | |
185 | <constant>NUL</constant> character before binding. For | |
186 | details, see | |
187 | <citerefentry project='man-pages'><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> | |
188 | ||
189 | <para>If the address string is a single number, it is read as | |
190 | port number to listen on via IPv6. Depending on the value of | |
191 | <varname>BindIPv6Only=</varname> (see below) this might result | |
192 | in the service being available via both IPv6 and IPv4 | |
193 | (default) or just via IPv6. | |
194 | </para> | |
195 | ||
196 | <para>If the address string is a string in the format | |
197 | v.w.x.y:z, it is read as IPv4 specifier for listening on an | |
198 | address v.w.x.y on a port z.</para> | |
199 | ||
200 | <para>If the address string is a string in the format [x]:y, | |
201 | it is read as IPv6 address x on a port y. Note that this might | |
202 | make the service available via IPv4, too, depending on the | |
203 | <varname>BindIPv6Only=</varname> setting (see below). | |
204 | </para> | |
205 | ||
359a5bcf SH |
206 | <para>If the address string is a string in the format |
207 | <literal>vsock:x:y</literal>, it is read as CID <literal>x</literal> on | |
208 | a port <literal>y</literal> address in the | |
209 | <constant>AF_VSOCK</constant> family. The CID is a unique 32-bit | |
210 | integer identifier in <constant>AF_VSOCK</constant> analogous to an IP | |
211 | address. Specifying the CID is optional, and may be set to the empty | |
212 | string.</para> | |
213 | ||
798d3a52 ZJS |
214 | <para>Note that <constant>SOCK_SEQPACKET</constant> (i.e. |
215 | <varname>ListenSequentialPacket=</varname>) is only available | |
216 | for <constant>AF_UNIX</constant> sockets. | |
217 | <constant>SOCK_STREAM</constant> (i.e. | |
218 | <varname>ListenStream=</varname>) when used for IP sockets | |
219 | refers to TCP sockets, <constant>SOCK_DGRAM</constant> (i.e. | |
220 | <varname>ListenDatagram=</varname>) to UDP.</para> | |
221 | ||
b938cb90 | 222 | <para>These options may be specified more than once, in which |
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223 | case incoming traffic on any of the sockets will trigger |
224 | service activation, and all listed sockets will be passed to | |
225 | the service, regardless of whether there is incoming traffic | |
226 | on them or not. If the empty string is assigned to any of | |
227 | these options, the list of addresses to listen on is reset, | |
228 | all prior uses of any of these options will have no | |
229 | effect.</para> | |
230 | ||
231 | <para>It is also possible to have more than one socket unit | |
232 | for the same service when using <varname>Service=</varname>, | |
233 | and the service will receive all the sockets configured in all | |
234 | the socket units. Sockets configured in one unit are passed in | |
235 | the order of configuration, but no ordering between socket | |
236 | units is specified.</para> | |
237 | ||
238 | <para>If an IP address is used here, it is often desirable to | |
239 | listen on it before the interface it is configured on is up | |
240 | and running, and even regardless of whether it will be up and | |
241 | running at any point. To deal with this, it is recommended to | |
242 | set the <varname>FreeBind=</varname> option described | |
243 | below.</para></listitem> | |
244 | </varlistentry> | |
245 | ||
246 | <varlistentry> | |
247 | <term><varname>ListenFIFO=</varname></term> | |
248 | <listitem><para>Specifies a file system FIFO to listen on. | |
249 | This expects an absolute file system path as argument. | |
250 | Behavior otherwise is very similar to the | |
251 | <varname>ListenDatagram=</varname> directive | |
252 | above.</para></listitem> | |
253 | </varlistentry> | |
254 | ||
255 | <varlistentry> | |
256 | <term><varname>ListenSpecial=</varname></term> | |
257 | <listitem><para>Specifies a special file in the file system to | |
258 | listen on. This expects an absolute file system path as | |
259 | argument. Behavior otherwise is very similar to the | |
260 | <varname>ListenFIFO=</varname> directive above. Use this to | |
261 | open character device nodes as well as special files in | |
262 | <filename>/proc</filename> and | |
263 | <filename>/sys</filename>.</para></listitem> | |
264 | </varlistentry> | |
265 | ||
266 | <varlistentry> | |
267 | <term><varname>ListenNetlink=</varname></term> | |
268 | <listitem><para>Specifies a Netlink family to create a socket | |
269 | for to listen on. This expects a short string referring to the | |
270 | <constant>AF_NETLINK</constant> family name (such as | |
271 | <varname>audit</varname> or <varname>kobject-uevent</varname>) | |
272 | as argument, optionally suffixed by a whitespace followed by a | |
273 | multicast group integer. Behavior otherwise is very similar to | |
274 | the <varname>ListenDatagram=</varname> directive | |
275 | above.</para></listitem> | |
276 | </varlistentry> | |
277 | ||
278 | <varlistentry> | |
279 | <term><varname>ListenMessageQueue=</varname></term> | |
280 | <listitem><para>Specifies a POSIX message queue name to listen | |
281 | on. This expects a valid message queue name (i.e. beginning | |
282 | with /). Behavior otherwise is very similar to the | |
283 | <varname>ListenFIFO=</varname> directive above. On Linux | |
284 | message queue descriptors are actually file descriptors and | |
285 | can be inherited between processes.</para></listitem> | |
286 | </varlistentry> | |
287 | ||
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288 | <varlistentry> |
289 | <term><varname>ListenUSBFunction=</varname></term> | |
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290 | <listitem><para>Specifies a <ulink |
291 | url="https://www.kernel.org/doc/Documentation/usb/functionfs.txt">USB | |
00bb64ec | 292 | FunctionFS</ulink> endpoints location to listen on, for |
3d314510 | 293 | implementation of USB gadget functions. This expects an |
00bb64ec PS |
294 | absolute file system path of functionfs mount point as the argument. |
295 | Behavior otherwise is very similar to the <varname>ListenFIFO=</varname> | |
a8eaaee7 | 296 | directive above. Use this to open the FunctionFS endpoint |
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297 | <filename>ep0</filename>. When using this option, the |
298 | activated service has to have the | |
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299 | <varname>USBFunctionDescriptors=</varname> and |
300 | <varname>USBFunctionStrings=</varname> options set. | |
81eb21b9 | 301 | </para></listitem> |
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302 | </varlistentry> |
303 | ||
74bb646e SS |
304 | <varlistentry> |
305 | <term><varname>SocketProtocol=</varname></term> | |
a7c64e14 | 306 | <listitem><para>Takes one of <option>udplite</option> |
74bb646e SS |
307 | or <option>sctp</option>. Specifies a socket protocol |
308 | (<constant>IPPROTO_UDPLITE</constant>) UDP-Lite | |
309 | (<constant>IPPROTO_SCTP</constant>) SCTP socket respectively. </para> | |
310 | </listitem> | |
311 | </varlistentry> | |
312 | ||
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313 | <varlistentry> |
314 | <term><varname>BindIPv6Only=</varname></term> | |
a7c64e14 | 315 | <listitem><para>Takes one of <option>default</option>, |
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316 | <option>both</option> or <option>ipv6-only</option>. Controls |
317 | the IPV6_V6ONLY socket option (see | |
3ba3a79d | 318 | <citerefentry project='die-net'><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
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319 | for details). If <option>both</option>, IPv6 sockets bound |
320 | will be accessible via both IPv4 and IPv6. If | |
321 | <option>ipv6-only</option>, they will be accessible via IPv6 | |
322 | only. If <option>default</option> (which is the default, | |
323 | surprise!), the system wide default setting is used, as | |
324 | controlled by | |
325 | <filename>/proc/sys/net/ipv6/bindv6only</filename>, which in | |
326 | turn defaults to the equivalent of | |
327 | <option>both</option>.</para> | |
328 | </listitem> | |
329 | </varlistentry> | |
330 | ||
331 | <varlistentry> | |
332 | <term><varname>Backlog=</varname></term> | |
333 | <listitem><para>Takes an unsigned integer argument. Specifies | |
334 | the number of connections to queue that have not been accepted | |
335 | yet. This setting matters only for stream and sequential | |
336 | packet sockets. See | |
337 | <citerefentry><refentrytitle>listen</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
338 | for details. Defaults to SOMAXCONN (128).</para></listitem> | |
339 | </varlistentry> | |
340 | ||
341 | <varlistentry> | |
342 | <term><varname>BindToDevice=</varname></term> | |
343 | <listitem><para>Specifies a network interface name to bind | |
344 | this socket to. If set, traffic will only be accepted from the | |
345 | specified network interfaces. This controls the | |
c129bd5d LP |
346 | SO_BINDTODEVICE socket option (see <citerefentry |
347 | project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
45f09f93 | 348 | for details). If this option is used, an implicit dependency |
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349 | from this socket unit on the network interface device unit |
350 | (<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
c129bd5d LP |
351 | is created. Note that setting this parameter might result in |
352 | additional dependencies to be added to the unit (see | |
353 | above).</para></listitem> | |
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354 | </varlistentry> |
355 | ||
356 | <varlistentry> | |
357 | <term><varname>SocketUser=</varname></term> | |
358 | <term><varname>SocketGroup=</varname></term> | |
359 | ||
360 | <listitem><para>Takes a UNIX user/group name. When specified, | |
361 | all AF_UNIX sockets and FIFO nodes in the file system are | |
362 | owned by the specified user and group. If unset (the default), | |
363 | the nodes are owned by the root user/group (if run in system | |
364 | context) or the invoking user/group (if run in user context). | |
365 | If only a user is specified but no group, then the group is | |
366 | derived from the user's default group.</para></listitem> | |
367 | </varlistentry> | |
368 | ||
369 | <varlistentry> | |
370 | <term><varname>SocketMode=</varname></term> | |
371 | <listitem><para>If listening on a file system socket or FIFO, | |
372 | this option specifies the file system access mode used when | |
373 | creating the file node. Takes an access mode in octal | |
374 | notation. Defaults to 0666.</para></listitem> | |
375 | </varlistentry> | |
376 | ||
377 | <varlistentry> | |
378 | <term><varname>DirectoryMode=</varname></term> | |
379 | <listitem><para>If listening on a file system socket or FIFO, | |
380 | the parent directories are automatically created if needed. | |
381 | This option specifies the file system access mode used when | |
382 | creating these directories. Takes an access mode in octal | |
383 | notation. Defaults to 0755.</para></listitem> | |
384 | </varlistentry> | |
385 | ||
386 | <varlistentry> | |
387 | <term><varname>Accept=</varname></term> | |
388 | <listitem><para>Takes a boolean argument. If true, a service | |
389 | instance is spawned for each incoming connection and only the | |
390 | connection socket is passed to it. If false, all listening | |
391 | sockets themselves are passed to the started service unit, and | |
392 | only one service unit is spawned for all connections (also see | |
393 | above). This value is ignored for datagram sockets and FIFOs | |
394 | where a single service unit unconditionally handles all | |
395 | incoming traffic. Defaults to <option>false</option>. For | |
396 | performance reasons, it is recommended to write new daemons | |
397 | only in a way that is suitable for | |
964c4eda | 398 | <option>Accept=no</option>. A daemon listening on an |
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399 | <constant>AF_UNIX</constant> socket may, but does not need to, |
400 | call | |
401 | <citerefentry><refentrytitle>close</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
402 | on the received socket before exiting. However, it must not | |
403 | unlink the socket from a file system. It should not invoke | |
404 | <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
964c4eda | 405 | on sockets it got with <varname>Accept=no</varname>, but it |
798d3a52 | 406 | may do so for sockets it got with |
964c4eda LP |
407 | <varname>Accept=yes</varname> set. Setting |
408 | <varname>Accept=yes</varname> is mostly useful to allow | |
798d3a52 | 409 | daemons designed for usage with |
b5c7d097 | 410 | <citerefentry project='freebsd'><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 | 411 | to work unmodified with systemd socket |
3b1c5241 SL |
412 | activation.</para> |
413 | ||
b938cb90 | 414 | <para>For IPv4 and IPv6 connections, the <varname>REMOTE_ADDR</varname> |
a8eaaee7 | 415 | environment variable will contain the remote IP address, and <varname>REMOTE_PORT</varname> |
3b1c5241 | 416 | will contain the remote port. This is the same as the format used by CGI. |
b938cb90 | 417 | For SOCK_RAW, the port is the IP protocol.</para></listitem> |
798d3a52 ZJS |
418 | </varlistentry> |
419 | ||
55301ec0 LP |
420 | <varlistentry> |
421 | <term><varname>Writable=</varname></term> | |
422 | <listitem><para>Takes a boolean argument. May only be used in | |
423 | conjunction with <varname>ListenSpecial=</varname>. If true, | |
424 | the specified special file is opened in read-write mode, if | |
b938cb90 | 425 | false, in read-only mode. Defaults to false.</para></listitem> |
55301ec0 LP |
426 | </varlistentry> |
427 | ||
798d3a52 ZJS |
428 | <varlistentry> |
429 | <term><varname>MaxConnections=</varname></term> | |
430 | <listitem><para>The maximum number of connections to | |
431 | simultaneously run services instances for, when | |
964c4eda | 432 | <option>Accept=yes</option> is set. If more concurrent |
798d3a52 ZJS |
433 | connections are coming in, they will be refused until at least |
434 | one existing connection is terminated. This setting has no | |
435 | effect on sockets configured with | |
964c4eda | 436 | <option>Accept=no</option> or datagram sockets. Defaults to |
798d3a52 ZJS |
437 | 64.</para></listitem> |
438 | </varlistentry> | |
439 | ||
440 | <varlistentry> | |
9d565427 SS |
441 | <term><varname>MaxConnectionsPerSource=</varname></term> |
442 | <listitem><para>The maximum number of connections for a service per source IP address. | |
cfaf4b75 | 443 | This is very similar to the <varname>MaxConnections=</varname> directive |
9d565427 SS |
444 | above. Disabled by default.</para> |
445 | </listitem> | |
446 | </varlistentry> | |
447 | ||
448 | <varlistentry> | |
798d3a52 ZJS |
449 | <term><varname>KeepAlive=</varname></term> |
450 | <listitem><para>Takes a boolean argument. If true, the TCP/IP | |
451 | stack will send a keep alive message after 2h (depending on | |
452 | the configuration of | |
453 | <filename>/proc/sys/net/ipv4/tcp_keepalive_time</filename>) | |
454 | for all TCP streams accepted on this socket. This controls the | |
455 | SO_KEEPALIVE socket option (see | |
3ba3a79d | 456 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
457 | and the <ulink |
458 | url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP | |
459 | Keepalive HOWTO</ulink> for details.) Defaults to | |
460 | <option>false</option>.</para></listitem> | |
461 | </varlistentry> | |
462 | ||
463 | <varlistentry> | |
464 | <term><varname>KeepAliveTimeSec=</varname></term> | |
b938cb90 | 465 | <listitem><para>Takes time (in seconds) as argument. The connection needs to remain |
798d3a52 ZJS |
466 | idle before TCP starts sending keepalive probes. This controls the TCP_KEEPIDLE |
467 | socket option (see | |
3ba3a79d | 468 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
469 | and the <ulink |
470 | url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP | |
471 | Keepalive HOWTO</ulink> for details.) | |
472 | Defaults value is 7200 seconds (2 hours).</para></listitem> | |
473 | </varlistentry> | |
474 | ||
475 | <varlistentry> | |
476 | <term><varname>KeepAliveIntervalSec=</varname></term> | |
477 | <listitem><para>Takes time (in seconds) as argument between | |
478 | individual keepalive probes, if the socket option SO_KEEPALIVE | |
a8eaaee7 | 479 | has been set on this socket. This controls |
798d3a52 | 480 | the TCP_KEEPINTVL socket option (see |
3ba3a79d | 481 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
482 | and the <ulink |
483 | url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP | |
484 | Keepalive HOWTO</ulink> for details.) Defaults value is 75 | |
485 | seconds.</para></listitem> | |
486 | </varlistentry> | |
487 | ||
488 | <varlistentry> | |
489 | <term><varname>KeepAliveProbes=</varname></term> | |
7ca41557 | 490 | <listitem><para>Takes an integer as argument. It is the number of |
798d3a52 ZJS |
491 | unacknowledged probes to send before considering the |
492 | connection dead and notifying the application layer. This | |
493 | controls the TCP_KEEPCNT socket option (see | |
3ba3a79d | 494 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
495 | and the <ulink |
496 | url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP | |
497 | Keepalive HOWTO</ulink> for details.) Defaults value is | |
498 | 9.</para></listitem> | |
499 | </varlistentry> | |
500 | ||
501 | <varlistentry> | |
502 | <term><varname>NoDelay=</varname></term> | |
503 | <listitem><para>Takes a boolean argument. TCP Nagle's | |
504 | algorithm works by combining a number of small outgoing | |
505 | messages, and sending them all at once. This controls the | |
506 | TCP_NODELAY socket option (see | |
3ba3a79d | 507 | <citerefentry project='die-net'><refentrytitle>tcp</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
508 | Defaults to <option>false</option>.</para></listitem> |
509 | </varlistentry> | |
510 | ||
511 | <varlistentry> | |
512 | <term><varname>Priority=</varname></term> | |
513 | <listitem><para>Takes an integer argument controlling the | |
514 | priority for all traffic sent from this socket. This controls | |
515 | the SO_PRIORITY socket option (see | |
3ba3a79d | 516 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
517 | for details.).</para></listitem> |
518 | </varlistentry> | |
519 | ||
520 | <varlistentry> | |
521 | <term><varname>DeferAcceptSec=</varname></term> | |
522 | ||
523 | <listitem><para>Takes time (in seconds) as argument. If set, | |
524 | the listening process will be awakened only when data arrives | |
525 | on the socket, and not immediately when connection is | |
526 | established. When this option is set, the | |
527 | <constant>TCP_DEFER_ACCEPT</constant> socket option will be | |
528 | used (see | |
3ba3a79d | 529 | <citerefentry project='die-net'><refentrytitle>tcp</refentrytitle><manvolnum>7</manvolnum></citerefentry>), |
798d3a52 ZJS |
530 | and the kernel will ignore initial ACK packets without any |
531 | data. The argument specifies the approximate amount of time | |
532 | the kernel should wait for incoming data before falling back | |
2dd67817 | 533 | to the normal behavior of honoring empty ACK packets. This |
798d3a52 ZJS |
534 | option is beneficial for protocols where the client sends the |
535 | data first (e.g. HTTP, in contrast to SMTP), because the | |
536 | server process will not be woken up unnecessarily before it | |
537 | can take any action. | |
538 | </para> | |
539 | ||
540 | <para>If the client also uses the | |
541 | <constant>TCP_DEFER_ACCEPT</constant> option, the latency of | |
542 | the initial connection may be reduced, because the kernel will | |
543 | send data in the final packet establishing the connection (the | |
544 | third packet in the "three-way handshake").</para> | |
545 | ||
546 | <para>Disabled by default.</para> | |
547 | </listitem> | |
548 | </varlistentry> | |
549 | ||
550 | <varlistentry> | |
551 | <term><varname>ReceiveBuffer=</varname></term> | |
552 | <term><varname>SendBuffer=</varname></term> | |
553 | <listitem><para>Takes an integer argument controlling the | |
554 | receive or send buffer sizes of this socket, respectively. | |
555 | This controls the SO_RCVBUF and SO_SNDBUF socket options (see | |
3ba3a79d | 556 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
557 | for details.). The usual suffixes K, M, G are supported and |
558 | are understood to the base of 1024.</para></listitem> | |
559 | </varlistentry> | |
560 | ||
561 | <varlistentry> | |
562 | <term><varname>IPTOS=</varname></term> | |
563 | <listitem><para>Takes an integer argument controlling the IP | |
564 | Type-Of-Service field for packets generated from this socket. | |
565 | This controls the IP_TOS socket option (see | |
3ba3a79d | 566 | <citerefentry project='die-net'><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
567 | for details.). Either a numeric string or one of |
568 | <option>low-delay</option>, <option>throughput</option>, | |
569 | <option>reliability</option> or <option>low-cost</option> may | |
570 | be specified.</para></listitem> | |
571 | </varlistentry> | |
572 | ||
573 | <varlistentry> | |
574 | <term><varname>IPTTL=</varname></term> | |
575 | <listitem><para>Takes an integer argument controlling the IPv4 | |
576 | Time-To-Live/IPv6 Hop-Count field for packets generated from | |
577 | this socket. This sets the IP_TTL/IPV6_UNICAST_HOPS socket | |
578 | options (see | |
3ba3a79d | 579 | <citerefentry project='die-net'><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 | 580 | and |
3ba3a79d | 581 | <citerefentry project='die-net'><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
582 | for details.)</para></listitem> |
583 | </varlistentry> | |
584 | ||
585 | <varlistentry> | |
586 | <term><varname>Mark=</varname></term> | |
587 | <listitem><para>Takes an integer value. Controls the firewall | |
588 | mark of packets generated by this socket. This can be used in | |
589 | the firewall logic to filter packets from this socket. This | |
590 | sets the SO_MARK socket option. See | |
3ba3a79d | 591 | <citerefentry project='die-net'><refentrytitle>iptables</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
592 | for details.</para></listitem> |
593 | </varlistentry> | |
594 | ||
595 | <varlistentry> | |
596 | <term><varname>ReusePort=</varname></term> | |
597 | <listitem><para>Takes a boolean value. If true, allows | |
598 | multiple | |
599 | <citerefentry><refentrytitle>bind</refentrytitle><manvolnum>2</manvolnum></citerefentry>s | |
600 | to this TCP or UDP port. This controls the SO_REUSEPORT socket | |
601 | option. See | |
3ba3a79d | 602 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
798d3a52 ZJS |
603 | for details.</para></listitem> |
604 | </varlistentry> | |
605 | ||
606 | <varlistentry> | |
607 | <term><varname>SmackLabel=</varname></term> | |
608 | <term><varname>SmackLabelIPIn=</varname></term> | |
609 | <term><varname>SmackLabelIPOut=</varname></term> | |
610 | <listitem><para>Takes a string value. Controls the extended | |
611 | attributes <literal>security.SMACK64</literal>, | |
612 | <literal>security.SMACK64IPIN</literal> and | |
613 | <literal>security.SMACK64IPOUT</literal>, respectively, i.e. | |
614 | the security label of the FIFO, or the security label for the | |
615 | incoming or outgoing connections of the socket, respectively. | |
616 | See <ulink | |
617 | url="https://www.kernel.org/doc/Documentation/security/Smack.txt">Smack.txt</ulink> | |
618 | for details.</para></listitem> | |
619 | </varlistentry> | |
620 | ||
621 | <varlistentry> | |
622 | <term><varname>SELinuxContextFromNet=</varname></term> | |
623 | <listitem><para>Takes a boolean argument. When true, systemd | |
624 | will attempt to figure out the SELinux label used for the | |
625 | instantiated service from the information handed by the peer | |
626 | over the network. Note that only the security level is used | |
627 | from the information provided by the peer. Other parts of the | |
628 | resulting SELinux context originate from either the target | |
629 | binary that is effectively triggered by socket unit or from | |
630 | the value of the <varname>SELinuxContext=</varname> option. | |
631 | This configuration option only affects sockets with | |
632 | <varname>Accept=</varname> mode set to | |
633 | <literal>true</literal>. Also note that this option is useful | |
634 | only when MLS/MCS SELinux policy is deployed. Defaults to | |
635 | <literal>false</literal>. </para></listitem> | |
636 | </varlistentry> | |
637 | ||
638 | <varlistentry> | |
639 | <term><varname>PipeSize=</varname></term> | |
640 | <listitem><para>Takes a size in bytes. Controls the pipe | |
641 | buffer size of FIFOs configured in this socket unit. See | |
642 | <citerefentry><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
643 | for details. The usual suffixes K, M, G are supported and are | |
644 | understood to the base of 1024.</para></listitem> | |
645 | </varlistentry> | |
646 | ||
647 | <varlistentry> | |
648 | <term><varname>MessageQueueMaxMessages=</varname>, | |
649 | <varname>MessageQueueMessageSize=</varname></term> | |
650 | <listitem><para>These two settings take integer values and | |
651 | control the mq_maxmsg field or the mq_msgsize field, | |
652 | respectively, when creating the message queue. Note that | |
653 | either none or both of these variables need to be set. See | |
3ba3a79d | 654 | <citerefentry project='die-net'><refentrytitle>mq_setattr</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
798d3a52 ZJS |
655 | for details.</para></listitem> |
656 | </varlistentry> | |
657 | ||
658 | <varlistentry> | |
659 | <term><varname>FreeBind=</varname></term> | |
660 | <listitem><para>Takes a boolean value. Controls whether the | |
661 | socket can be bound to non-local IP addresses. This is useful | |
662 | to configure sockets listening on specific IP addresses before | |
663 | those IP addresses are successfully configured on a network | |
664 | interface. This sets the IP_FREEBIND socket option. For | |
665 | robustness reasons it is recommended to use this option | |
666 | whenever you bind a socket to a specific IP address. Defaults | |
667 | to <option>false</option>.</para></listitem> | |
668 | </varlistentry> | |
669 | ||
670 | <varlistentry> | |
671 | <term><varname>Transparent=</varname></term> | |
672 | <listitem><para>Takes a boolean value. Controls the | |
673 | IP_TRANSPARENT socket option. Defaults to | |
674 | <option>false</option>.</para></listitem> | |
675 | </varlistentry> | |
676 | ||
677 | <varlistentry> | |
678 | <term><varname>Broadcast=</varname></term> | |
679 | <listitem><para>Takes a boolean value. This controls the | |
680 | SO_BROADCAST socket option, which allows broadcast datagrams | |
681 | to be sent from this socket. Defaults to | |
682 | <option>false</option>.</para></listitem> | |
683 | </varlistentry> | |
684 | ||
685 | <varlistentry> | |
686 | <term><varname>PassCredentials=</varname></term> | |
687 | <listitem><para>Takes a boolean value. This controls the | |
688 | SO_PASSCRED socket option, which allows | |
689 | <constant>AF_UNIX</constant> sockets to receive the | |
690 | credentials of the sending process in an ancillary message. | |
691 | Defaults to <option>false</option>.</para></listitem> | |
692 | </varlistentry> | |
693 | ||
694 | <varlistentry> | |
695 | <term><varname>PassSecurity=</varname></term> | |
696 | <listitem><para>Takes a boolean value. This controls the | |
697 | SO_PASSSEC socket option, which allows | |
698 | <constant>AF_UNIX</constant> sockets to receive the security | |
699 | context of the sending process in an ancillary message. | |
700 | Defaults to <option>false</option>.</para></listitem> | |
701 | </varlistentry> | |
702 | ||
703 | <varlistentry> | |
704 | <term><varname>TCPCongestion=</varname></term> | |
705 | <listitem><para>Takes a string value. Controls the TCP | |
706 | congestion algorithm used by this socket. Should be one of | |
707 | "westwood", "veno", "cubic", "lp" or any other available | |
708 | algorithm supported by the IP stack. This setting applies only | |
709 | to stream sockets.</para></listitem> | |
710 | </varlistentry> | |
711 | ||
712 | <varlistentry> | |
713 | <term><varname>ExecStartPre=</varname></term> | |
714 | <term><varname>ExecStartPost=</varname></term> | |
715 | <listitem><para>Takes one or more command lines, which are | |
716 | executed before or after the listening sockets/FIFOs are | |
717 | created and bound, respectively. The first token of the | |
718 | command line must be an absolute filename, then followed by | |
719 | arguments for the process. Multiple command lines may be | |
720 | specified following the same scheme as used for | |
721 | <varname>ExecStartPre=</varname> of service unit | |
722 | files.</para></listitem> | |
723 | </varlistentry> | |
724 | ||
725 | <varlistentry> | |
726 | <term><varname>ExecStopPre=</varname></term> | |
727 | <term><varname>ExecStopPost=</varname></term> | |
728 | <listitem><para>Additional commands that are executed before | |
729 | or after the listening sockets/FIFOs are closed and removed, | |
730 | respectively. Multiple command lines may be specified | |
731 | following the same scheme as used for | |
732 | <varname>ExecStartPre=</varname> of service unit | |
733 | files.</para></listitem> | |
734 | </varlistentry> | |
735 | ||
736 | <varlistentry> | |
737 | <term><varname>TimeoutSec=</varname></term> | |
738 | <listitem><para>Configures the time to wait for the commands | |
739 | specified in <varname>ExecStartPre=</varname>, | |
740 | <varname>ExecStartPost=</varname>, | |
741 | <varname>ExecStopPre=</varname> and | |
742 | <varname>ExecStopPost=</varname> to finish. If a command does | |
743 | not exit within the configured time, the socket will be | |
744 | considered failed and be shut down again. All commands still | |
745 | running will be terminated forcibly via | |
746 | <constant>SIGTERM</constant>, and after another delay of this | |
747 | time with <constant>SIGKILL</constant>. (See | |
748 | <option>KillMode=</option> in | |
749 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.) | |
750 | Takes a unit-less value in seconds, or a time span value such | |
751 | as "5min 20s". Pass <literal>0</literal> to disable the | |
752 | timeout logic. Defaults to | |
753 | <varname>DefaultTimeoutStartSec=</varname> from the manager | |
754 | configuration file (see | |
755 | <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>). | |
756 | </para></listitem> | |
757 | </varlistentry> | |
758 | ||
759 | <varlistentry> | |
760 | <term><varname>Service=</varname></term> | |
761 | <listitem><para>Specifies the service unit name to activate on | |
762 | incoming traffic. This setting is only allowed for sockets | |
763 | with <varname>Accept=no</varname>. It defaults to the service | |
764 | that bears the same name as the socket (with the suffix | |
765 | replaced). In most cases, it should not be necessary to use | |
c129bd5d LP |
766 | this option. Note that setting this parameter might result in |
767 | additional dependencies to be added to the unit (see | |
768 | above).</para></listitem> | |
798d3a52 ZJS |
769 | </varlistentry> |
770 | ||
771 | <varlistentry> | |
772 | <term><varname>RemoveOnStop=</varname></term> | |
773 | <listitem><para>Takes a boolean argument. If enabled, any file | |
774 | nodes created by this socket unit are removed when it is | |
775 | stopped. This applies to AF_UNIX sockets in the file system, | |
776 | POSIX message queues, FIFOs, as well as any symlinks to them | |
777 | configured with <varname>Symlinks=</varname>. Normally, it | |
778 | should not be necessary to use this option, and is not | |
779 | recommended as services might continue to run after the socket | |
780 | unit has been terminated and it should still be possible to | |
781 | communicate with them via their file system node. Defaults to | |
782 | off.</para></listitem> | |
783 | </varlistentry> | |
784 | ||
785 | <varlistentry> | |
786 | <term><varname>Symlinks=</varname></term> | |
3ecc7fc3 LP |
787 | <listitem><para>Takes a list of file system paths. The specified paths will be created as symlinks to the |
788 | <constant>AF_UNIX</constant> socket path or FIFO path of this socket unit. If this setting is used, only one | |
789 | <constant>AF_UNIX</constant> socket in the file system or one FIFO may be configured for the socket unit. Use | |
790 | this option to manage one or more symlinked alias names for a socket, binding their lifecycle together. Note | |
791 | that if creation of a symlink fails this is not considered fatal for the socket unit, and the socket unit may | |
792 | still start. If an empty string is assigned, the list of paths is reset. Defaults to an empty | |
793 | list.</para></listitem> | |
798d3a52 ZJS |
794 | </varlistentry> |
795 | ||
8dd4c05b LP |
796 | <varlistentry> |
797 | <term><varname>FileDescriptorName=</varname></term> | |
798 | <listitem><para>Assigns a name to all file descriptors this | |
799 | socket unit encapsulates. This is useful to help activated | |
a8eaaee7 | 800 | services identify specific file descriptors, if multiple fds |
8dd4c05b LP |
801 | are passed. Services may use the |
802 | <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
803 | call to acquire the names configured for the received file | |
804 | descriptors. Names may contain any ASCII character, but must | |
a8eaaee7 | 805 | exclude control characters and <literal>:</literal>, and must |
8dd4c05b | 806 | be at most 255 characters in length. If this setting is not |
b938cb90 | 807 | used, the file descriptor name defaults to the name of the |
8dd4c05b LP |
808 | socket unit, including its <filename>.socket</filename> |
809 | suffix.</para></listitem> | |
810 | </varlistentry> | |
811 | ||
8b26cdbd LP |
812 | <varlistentry> |
813 | <term><varname>TriggerLimitIntervalSec=</varname></term> | |
db985064 | 814 | <term><varname>TriggerLimitBurst=</varname></term> |
8b26cdbd LP |
815 | |
816 | <listitem><para>Configures a limit on how often this socket unit my be activated within a specific time | |
817 | interval. The <varname>TriggerLimitIntervalSec=</varname> may be used to configure the length of the time | |
818 | interval in the usual time units <literal>us</literal>, <literal>ms</literal>, <literal>s</literal>, | |
1f15ce28 | 819 | <literal>min</literal>, <literal>h</literal>, … and defaults to 2s (See |
8b26cdbd | 820 | <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details on |
1f15ce28 LP |
821 | the various time units understood). The <varname>TriggerLimitBurst=</varname> setting takes a positive integer |
822 | value and specifies the number of permitted activations per time interval, and defaults to 200 for | |
823 | <varname>Accept=yes</varname> sockets (thus by default permitting 200 activations per 2s), and 20 otherwise (20 | |
824 | activations per 2s). Set either to 0 to disable any form of trigger rate limiting. If the limit is hit, the | |
825 | socket unit is placed into a failure mode, and will not be connectible anymore until restarted. Note that this | |
826 | limit is enforced before the service activation is enqueued.</para></listitem> | |
8b26cdbd LP |
827 | </varlistentry> |
828 | ||
798d3a52 ZJS |
829 | </variablelist> |
830 | ||
831 | <para>Check | |
832 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
833 | and | |
834 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
835 | for more settings.</para> | |
836 | ||
837 | </refsect1> | |
838 | ||
839 | <refsect1> | |
840 | <title>See Also</title> | |
841 | <para> | |
842 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
843 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
844 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
845 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
846 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
847 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
848 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
8dd4c05b LP |
849 | <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
850 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
851 | <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
798d3a52 | 852 | </para> |
798d3a52 ZJS |
853 | <para> |
854 | For more extensive descriptions see the "systemd for Developers" series: | |
855 | <ulink url="http://0pointer.de/blog/projects/socket-activation.html">Socket Activation</ulink>, | |
856 | <ulink url="http://0pointer.de/blog/projects/socket-activation2.html">Socket Activation, part II</ulink>, | |
857 | <ulink url="http://0pointer.de/blog/projects/inetd.html">Converting inetd Services</ulink>, | |
858 | <ulink url="http://0pointer.de/blog/projects/socket-activated-containers.html">Socket Activated Internet Services and OS Containers</ulink>. | |
859 | </para> | |
860 | </refsect1> | |
1f812fea LP |
861 | |
862 | </refentry> |