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1 <?xml version="1.0"?>
2 <!--*-nxml-*-->
3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
4      "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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8   Copyright 2013 David Strauss
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23 <refentry id="systemd-sabridge">
24         <refentryinfo>
25                 <title>systemd-sabridge</title>
26                 <productname>systemd</productname>
27                 <authorgroup>
28                         <author>
29                                 <contrib>Developer</contrib>
30                                 <firstname>David</firstname>
31                                 <surname>Strauss</surname>
32                                 <email>david@davidstrauss.net</email>
33                         </author>
34                 </authorgroup>
35         </refentryinfo>
36         <refmeta>
37                 <refentrytitle>systemd-sabridge</refentrytitle>
38                 <manvolnum>1</manvolnum>
39         </refmeta>
40         <refnamediv>
41                 <refname>systemd-sabridge</refname>
42                 <refpurpose>Inherit a socket. Bidirectionally
43                 proxy.</refpurpose>
44         </refnamediv>
45         <refsynopsisdiv>
46                 <cmdsynopsis>
47                         <command>systemd-sabridge</command>
48                         <arg choice="opt" rep="repeat">OPTIONS</arg>
49                         <arg choice="plain"><replaceable>HOSTNAME-OR-IP</replaceable></arg>
50                         <arg choice="plain"><replaceable>PORT-OR-SERVICE</replaceable></arg>
51                 </cmdsynopsis>
52                 <cmdsynopsis>
53                         <command>systemd-sabridge</command>
54                         <arg choice="opt" rep="repeat">OPTIONS</arg>
55                         <arg choice="plain"><replaceable>UNIX-DOMAIN-SOCKET-PATH</replaceable>
56                         </arg>
57                 </cmdsynopsis>
58         </refsynopsisdiv>
59         <refsect1>
60                 <title>Description</title>
61                 <para>
62                 <command>systemd-sabridge</command>provides a proxy
63                 to socket-activate services that do not yet support
64                 native socket activation. On behalf of the daemon,
65                 the proxy inherits the socket from systemd, accepts
66                 each client connection, opens a connection to the server
67                 for each client, and then bidirectionally forwards
68                 data between the two.</para>
69                 <para>This utility's behavior is similar to
70                 <citerefentry><refentrytitle>socat</refentrytitle><manvolnum>1</manvolnum> </citerefentry>.
71                 The main differences for <command>systemd-sabridge</command>
72                 are support for socket activation with
73                 <literal>Accept=false</literal> and an event-driven
74                 design that scales better with the number of
75                 connections.</para>
76         </refsect1>
77         <refsect1>
78                 <title>Options</title>
79                 <para>The following options are understood:</para>
80                 <variablelist>
81                         <varlistentry>
82                                 <term><option>-h</option></term>
83                                 <term><option>--help</option></term>
84                                 <listitem>
85                                         <para>Prints a short help
86                                         text and exits.</para>
87                                 </listitem>
88                         </varlistentry>
89                         <varlistentry>
90                                 <term><option>--version</option></term>
91                                 <listitem>
92                                         <para>Prints a version
93                                         string and exits.</para>
94                                 </listitem>
95                         </varlistentry>
96                         <varlistentry>
97                                 <term><option>--ignore-env</option></term>
98                                 <listitem>
99                                         <para>Skips verification of
100                                         the expected PID and file
101                                         descriptor numbers. Use if
102                                         invoked indirectly, for
103                                         example with a shell script
104                                         rather than with
105                                         <option>ExecStart=/usr/bin/systemd-sabridge</option>
106                                         </para>
107                                 </listitem>
108                         </varlistentry>
109                 </variablelist>
110         </refsect1>
111         <refsect1>
112                 <title>Exit status</title>
113                 <para>On success 0 is returned, a non-zero failure
114                 code otherwise.</para>
115         </refsect1>
116         <refsect1>
117                 <title>Examples</title>
118                 <refsect2>
119                         <title>Direct-Use Example</title>
120                         <para>Use two services with a dependency
121                         and no namespace isolation.</para>
122                         <example label="bridge socket unit">
123                                 <title>/etc/systemd/system/bridge-to-nginx.socket</title>
124                                 <programlisting>
125 <![CDATA[[Socket]
126 ListenStream=80
127
128 [Install]
129 WantedBy=socket.target]]>
130 </programlisting>
131                         </example>
132                         <example label="bridge service unit">
133                                 <title>/etc/systemd/system/bridge-to-nginx.service</title>
134                                 <programlisting>
135 <![CDATA[[Unit]
136 After=nginx.service
137 Requires=nginx.service
138
139 [Service]
140 ExecStart=/usr/bin/systemd-sabridge /tmp/nginx.sock
141 PrivateTmp=true
142 PrivateNetwork=true]]>
143 </programlisting>
144                         </example>
145                         <example label="nginx configuration">
146                                 <title>/etc/nginx/nginx.conf</title>
147                                 <programlisting>
148 <![CDATA[[...]
149 server {
150     listen       unix:/tmp/nginx.sock;
151     [...]]]>
152 </programlisting>
153                         </example>
154                         <example label="commands">
155                                 <programlisting>
156 <![CDATA[$ sudo systemctl --system daemon-reload
157 $ sudo systemctl start bridge-to-nginx.socket
158 $ sudo systemctl enable bridge-to-nginx.socket
159 $ curl http://localhost:80/]]>
160 </programlisting>
161                         </example>
162                 </refsect2>
163                 <refsect2>
164                         <title>Indirect-Use Example</title>
165                         <para>Use a shell script to isolate the
166                         service and bridge into the same namespace.
167                         This is particularly useful for running
168                         TCP-only daemons without the daemon
169                         affecting ports on regular
170                         interfaces.</para>
171                         <example label="combined bridge and nginx socket unit">
172
173                                 <title>
174                                 /etc/systemd/system/bridge-with-nginx.socket</title>
175                                 <programlisting>
176 <![CDATA[[Socket]
177 ListenStream=80
178
179 [Install]
180 WantedBy=socket.target]]>
181 </programlisting>
182                         </example>
183                         <example label="combined bridge and nginx service unit">
184
185                                 <title>
186                                 /etc/systemd/system/bridge-with-nginx.service</title>
187                                 <programlisting>
188 <![CDATA[[Unit]
189 After=syslog.target remote-fs.target nss-lookup.target
190
191 [Service]
192 ExecStartPre=/usr/sbin/nginx -t
193 ExecStart=/usr/bin/sabridge-nginx.sh
194 PrivateTmp=true
195 PrivateNetwork=true]]>
196 </programlisting>
197                         </example>
198                         <example label="shell script">
199                                 <title>
200                                 /usr/bin/sabridge-nginx.sh</title>
201                                 <programlisting>
202 <![CDATA[#!/bin/sh
203 /usr/sbin/nginx
204 while [ ! -f /tmp/nginx.pid ]
205   do
206      /usr/bin/inotifywait /tmp/nginx.pid
207   done
208 /usr/bin/systemd-sabridge --ignore-env localhost 8080]]>
209 </programlisting>
210                         </example>
211                         <example label="nginx configuration">
212                                 <title>
213                                 /etc/nginx/nginx.conf</title>
214                                 <programlisting>
215 <![CDATA[[...]
216 server {
217     listen       8080;
218     listen       unix:/tmp/nginx.sock;
219     [...]]]>
220 </programlisting>
221                         </example>
222                         <example label="commands">
223                                 <programlisting>
224 <![CDATA[$ sudo systemctl --system daemon-reload
225 $ sudo systemctl start bridge-with-nginx.socket
226 $ sudo systemctl enable bridge-with-nginx.socket
227 $ curl http://localhost:80/]]>
228 </programlisting>
229                         </example>
230                 </refsect2>
231         </refsect1>
232         <refsect1>
233                 <title>See Also</title>
234                 <para>
235                 <citerefentry>
236                         <refentrytitle>
237                         systemd.service</refentrytitle>
238                         <manvolnum>5</manvolnum>
239                 </citerefentry>,
240                 <citerefentry>
241                         <refentrytitle>
242                         systemd.socket</refentrytitle>
243                         <manvolnum>5</manvolnum>
244                 </citerefentry>,
245                 <citerefentry>
246                         <refentrytitle>systemctl</refentrytitle>
247                         <manvolnum>1</manvolnum>
248                 </citerefentry>,
249                 <citerefentry>
250                         <refentrytitle>socat</refentrytitle>
251                         <manvolnum>1</manvolnum>
252                 </citerefentry></para>
253         </refsect1>
254 </refentry>