chiark / gitweb /
man: wording and grammar updates
[elogind.git] / man / systemd.socket.xml
index 8cbb512..419a38c 100644 (file)
@@ -9,16 +9,16 @@
   Copyright 2010 Lennart Poettering
 
   systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
   (at your option) any later version.
 
   systemd is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  General Public License for more details.
+  Lesser General Public License for more details.
 
-  You should have received a copy of the GNU General Public License
+  You should have received a copy of the GNU Lesser General Public License
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 -->
 
 
         <refnamediv>
                 <refname>systemd.socket</refname>
-                <refpurpose>systemd socket configuration files</refpurpose>
+                <refpurpose>Socket unit configuration</refpurpose>
         </refnamediv>
 
         <refsynopsisdiv>
-                <para><filename>systemd.socket</filename></para>
+                <para><filename><replaceable>socket</replaceable>.socket</filename></para>
         </refsynopsisdiv>
 
         <refsect1>
                 <title>Description</title>
 
                 <para>A unit configuration file whose name ends in
-                <filename>.socket</filename> encodes information about
+                <literal>.socket</literal> encodes information about
                 an IPC or network socket or a file system FIFO
                 controlled and supervised by systemd, for socket-based
                 activation.</para>
                 <option>ExecStartPre=</option>,
                 <option>ExecStartPost=</option>,
                 <option>ExecStopPre=</option> and
-                <option>ExecStoptPost=</option> commands are executed
-                in.</para>
+                <option>ExecStopPost=</option> commands are executed
+                in, and in
+                <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                which define the way the processes are
+                terminated, and in
+                <citerefentry><refentrytitle>systemd.cgroup</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                which configure control group settings for the
+                processes of the service.</para>
 
                 <para>For each socket file a matching service file
                 (see
@@ -90,7 +96,7 @@
                 <filename>foo.socket</filename> needs a matching
                 service <filename>foo.service</filename> if
                 <option>Accept=false</option> is set. If
-                <option>Accept=true</option> is set a service template
+                <option>Accept=true</option> is set, a service template
                 file <filename>foo@.service</filename> must exist from
                 which services are instantiated for each incoming
                 connection.</para>
                 supervises. A number of options that may be used in
                 this section are shared with other unit types. These
                 options are documented in
-                <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
+                <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                and
+                <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
                 options specific to the [Socket] section of socket
                 units are the following:</para>
 
-                <variablelist>
+                <variablelist class='unit-directives'>
                         <varlistentry>
                                 <term><varname>ListenStream=</varname></term>
                                 <term><varname>ListenDatagram=</varname></term>
                                 <term><varname>ListenSequentialPacket=</varname></term>
                                 <listitem><para>Specifies an address
                                 to listen on for a stream
-                                (SOCK_STREAM), datagram (SOCK_DGRAM)
-                                resp. sequential packet
-                                (SOCK_SEQPACKET) socket. The address
+                                (<constant>SOCK_STREAM</constant>), datagram (<constant>SOCK_DGRAM</constant>),
+                                or sequential packet
+                                (<constant>SOCK_SEQPACKET</constant>) socket, respectively. The address
                                 can be written in various formats:</para>
 
                                 <para>If the address starts with a
-                                slash (/), it is read as file system
-                                socket in the AF_UNIX socket
+                                slash (<literal>/</literal>), it is read as file system
+                                socket in the <constant>AF_UNIX</constant> socket
                                 family.</para>
 
-                                <para>If the address starts with an
-                                ampersand (@) it is read as abstract
-                                namespace socket in the AF_UNIX
-                                family. The @ is replaced with a NUL
-                                character before binding. For details
-                                see
+                                <para>If the address starts with an at
+                                symbol (<literal>@</literal>), it is read as abstract
+                                namespace socket in the
+                                <constant>AF_UNIX</constant>
+                                family. The <literal>@</literal> is
+                                replaced with a
+                                <constant>NUL</constant> character
+                                before binding. For details, see
                                 <citerefentry><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 
                                 <para>If the address string is a
-                                single number it is read as port
-                                number to listen on for both IPv4 and
-                                IPv6.</para>
+                                single number, it is read as port
+                                number to listen on via
+                                IPv6. Depending on the value of
+                                <varname>BindIPv6Only=</varname> (see below) this
+                                might result in the service being
+                                available via both IPv6 and IPv4 (default) or
+                                just via IPv6.
+                                </para>
 
                                 <para>If the address string is a
-                                string in the format v.w.x.y:z it is
+                                string in the format v.w.x.y:z, it is
                                 read as IPv4 specifier for listening
                                 on an address v.w.x.y on a port
                                 z.</para>
 
                                 <para>If the address string is a
-                                string in the format [x]:y it is read
-                                as IPv6 address x on a port y.</para>
-
-                                <para>Note that SOCK_SEQPACKET
+                                string in the format [x]:y, it is read
+                                as IPv6 address x on a port y. Note
+                                that this might make the service
+                                available via IPv4, too, depending on
+                                the <varname>BindIPv6Only=</varname>
+                                setting (see below).
+                                </para>
+
+                                <para>Note that <constant>SOCK_SEQPACKET</constant>
                                 (i.e. <varname>ListenSequentialPacket=</varname>)
-                                is only available for AF_UNIX
-                                sockets. SOCK_STREAM
+                                is only available for <constant>AF_UNIX</constant>
+                                sockets. <constant>SOCK_STREAM</constant>
                                 (i.e. <varname>ListenStream=</varname>)
                                 when used for IP sockets refers to TCP
-                                sockets, SOCK_DGRAM
+                                sockets, <constant>SOCK_DGRAM</constant>
                                 (i.e. <varname>ListenDatagram=</varname>)
                                 to UDP.</para>
 
                                 <para>These options may be specified
                                 more than once in which case incoming
-                                traffic on any of the sockets will trigger
-                                service activation, and all listed
-                                sockets will be passed to the service,
-                                regardless whether there is incoming
-                                traffic on them or not.</para>
-
-                                <para>If an IP address is used here, it
-                                is often desirable to listen on it
+                                traffic on any of the sockets will
+                                trigger service activation, and all
+                                listed sockets will be passed to the
+                                service, regardless whether there is
+                                incoming traffic on them or not. If
+                                the empty string is assigned to any of
+                                these options, the list of addresses
+                                to listen on is reset, all prior uses
+                                of any of these options will have no
+                                effect.</para>
+
+                                <para>If an IP address is used here,
+                                it is often desirable to listen on it
                                 before the interface it is configured
                                 on is up and running, and even
                                 regardless whether it will be up and
-                                running ever at all. To deal with this it is
-                                recommended to set the
+                                running ever at all. To deal with this
+                                it is recommended to set the
                                 <varname>FreeBind=</varname> option
                                 described below.</para></listitem>
                         </varlistentry>
                                 <listitem><para>Specifies a file
                                 system FIFO to listen on. This expects
                                 an absolute file system path as
-                                argument. Behaviour otherwise is very
+                                argument. Behavior otherwise is very
                                 similar to the
                                 <varname>ListenDatagram=</varname>
                                 directive above.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>ListenSpecial=</varname></term>
+                                <listitem><para>Specifies a special
+                                file in the file system to listen
+                                on. This expects an absolute file
+                                system path as argument. Behavior
+                                otherwise is very similar to the
+                                <varname>ListenFIFO=</varname>
+                                directive above. Use this to open
+                                character device nodes as well as
+                                special files in
+                                <filename>/proc</filename> and
+                                <filename>/sys</filename>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>ListenNetlink=</varname></term>
+                                <listitem><para>Specifies a Netlink
+                                family to create a socket for to
+                                listen on. This expects a short string
+                                referring to the <constant>AF_NETLINK</constant> family
+                                name (such as <varname>audit</varname>
+                                or <varname>kobject-uevent</varname>)
+                                as argument, optionally suffixed by a
+                                whitespace followed by a multicast
+                                group integer. Behavior otherwise is
+                                very similar to the
+                                <varname>ListenDatagram=</varname>
+                                directive above.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>ListenMessageQueue=</varname></term>
+                                <listitem><para>Specifies a POSIX
+                                message queue name to listen on. This
+                                expects a valid message queue name
+                                (i.e. beginning with /). Behavior
+                                otherwise is very similar to the
+                                <varname>ListenFIFO=</varname>
+                                directive above. On Linux message
+                                queue descriptors are actually file
+                                descriptors and can be inherited
+                                between processes.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>BindIPv6Only=</varname></term>
                                 <listitem><para>Takes a one of
                                 <option>default</option>,
                                 <option>ipv6-only</option>, they will
                                 be accessible via IPv6 only. If
                                 <option>default</option> (which is the
-                                default, surprise!) the system wide
+                                default, surprise!), the system wide
                                 default setting is used, as controlled
                                 by
-                                <filename>/proc/sys/net/ipv6/bindv6only</filename>.</para>
+                                <filename>/proc/sys/net/ipv6/bindv6only</filename>,
+                                which in turn defaults to the
+                                equivalent of
+                                <option>both</option>.</para>
                                 </listitem>
                         </varlistentry>
 
                                 <term><varname>BindToDevice=</varname></term>
                                 <listitem><para>Specifies a network
                                 interface name to bind this socket
-                                to. If set traffic will only be
+                                to. If set, traffic will only be
                                 accepted from the specified network
                                 interfaces. This controls the
                                 SO_BINDTODEVICE socket option (see
                         <varlistentry>
                                 <term><varname>DirectoryMode=</varname></term>
                                 <listitem><para>If listening on a file
-                                system socket of FIFO, the parent
+                                system socket or FIFO, the parent
                                 directories are automatically created
                                 if needed. This option specifies the
                                 file system access mode used when
                         <varlistentry>
                                 <term><varname>SocketMode=</varname></term>
                                 <listitem><para>If listening on a file
-                                system socket of FIFO, this option
+                                system socket or FIFO, this option
                                 specifies the file system access mode
                                 used when creating the file
                                 node. Takes an access mode in octal
                                 and only one service unit is spawned
                                 for all connections (also see
                                 above). This value is ignored for
-                                datagram sockets and FIFOs where
-                                single service unit unconditionally
+                                datagram sockets and FIFOs where a
+                                single service unit unconditionally
                                 handles all incoming traffic. Defaults
                                 to <option>false</option>. For
                                 performance reasons, it is recommended
                                 to write new daemons only in a way
                                 that is suitable for
-                                <option>Accept=false</option>. This
-                                option is mostly useful to allow
-                                daemons designed for usage with
-                                <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+                                <option>Accept=false</option>. A
+                                daemon listening on an <constant>AF_UNIX</constant> socket
+                                may, but does not need to, call
+                                <citerefentry><refentrytitle>close</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                on the received socket before
+                                exiting. However, it must not unlink
+                                the socket from a file system. It
+                                should not invoke
+                                <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                on sockets it got with
+                                <varname>Accept=false</varname>, but
+                                it may do so for sockets it got with
+                                <varname>Accept=true</varname> set.
+                                Setting <varname>Accept=true</varname>
+                                is mostly useful to allow daemons
+                                designed for usage with
+                                <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                                 to work unmodified with systemd socket
                                 activation.</para></listitem>
                         </varlistentry>
                                 are coming in, they will be refused
                                 until at least one existing connection
                                 is terminated. This setting has no
-                                effect for sockets configured with
-                                <option>Accept=no</option> or datagram
+                                effect on sockets configured with
+                                <option>Accept=false</option> or datagram
                                 sockets. Defaults to
                                 64.</para></listitem>
                         </varlistentry>
                                 <term><varname>SendBuffer=</varname></term>
                                 <listitem><para>Takes an integer
                                 argument controlling the receive
-                                resp. send buffer sizes of this
-                                socket. This controls the SO_RCVBUF
-                                resp. SO_SNDBUF socket options (see
+                                or send buffer sizes of this
+                                socket, respectively. This controls the SO_RCVBUF
+                                and SO_SNDBUF socket options (see
                                 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                 for details.).</para></listitem>
                         </varlistentry>
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>ReusePort=</varname></term>
+                                <listitem><para>Takes a boolean
+                                value. If true, allows multiple <citerefentry><refentrytitle>bind</refentrytitle><manvolnum>2</manvolnum></citerefentry>s
+                                to this TCP or UDP port.  This
+                                controls the SO_REUSEPORT socket
+                                option.  See
+                                <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                for details.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>SmackLabel=</varname></term>
+                                <term><varname>SmackLabelIPIn=</varname></term>
+                                <term><varname>SmackLabelIPOut=</varname></term>
+                                <listitem><para>Takes a string
+                                value. Controls the extended
+                                attributes
+                                <literal>security.SMACK64</literal>,
+                                <literal>security.SMACK64IPIN</literal>
+                                and
+                                <literal>security.SMACK64IPOUT</literal>,
+                                respectively, i.e. the security label
+                                of the FIFO, or the security label for
+                                the incoming or outgoing connections
+                                of the socket, respectively. See
+                                <ulink
+                                url="https://www.kernel.org/doc/Documentation/security/Smack.txt">Smack.txt</ulink>
+                                for details.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>PipeSize=</varname></term>
                                 <listitem><para>Takes an integer
                                 value. Controls the pipe buffer size
                                 of FIFOs configured in this socket
-                                unit.  See
+                                unit. See
                                 <citerefentry><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                 for details.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>MessageQueueMaxMessages=</varname>,
+                                <varname>MessageQueueMessageSize=</varname></term>
+                                <listitem><para>These two settings
+                                take integer values and control the
+                                mq_maxmsg field or the mq_msgsize field, respectively, when
+                                creating the message queue. Note that
+                                either none or both of these variables
+                                need to be set. See
+                                <citerefentry><refentrytitle>mq_setattr</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                                for details.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>FreeBind=</varname></term>
                                 <listitem><para>Takes a boolean
                                 value. Controls whether the socket can
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>Transparent=</varname></term>
+                                <listitem><para>Takes a boolean
+                                value. Controls the IP_TRANSPARENT
+                                socket option. Defaults to
+                                <option>false</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>Broadcast=</varname></term>
+                                <listitem><para>Takes a boolean
+                                value. This controls the SO_BROADCAST
+                                socket option, which allows broadcast
+                                datagrams to be sent from this
+                                socket. Defaults to
+                                <option>false</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>PassCredentials=</varname></term>
+                                <listitem><para>Takes a boolean
+                                value. This controls the SO_PASSCRED
+                                socket option, which allows <constant>AF_UNIX</constant> sockets to
+                                receive the credentials of the sending
+                                process in an ancillary message.
+                                Defaults to
+                                <option>false</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>PassSecurity=</varname></term>
+                                <listitem><para>Takes a boolean
+                                value. This controls the SO_PASSSEC
+                                socket option, which allows <constant>AF_UNIX</constant>
+                                sockets to receive the security
+                                context of the sending process in an
+                                ancillary message. Defaults to
+                                <option>false</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>TCPCongestion=</varname></term>
                                 <listitem><para>Takes a string
                                 value. Controls the TCP congestion
                                 <term><varname>ExecStartPost=</varname></term>
                                 <listitem><para>Takes one or more
                                 command lines, which are executed
-                                before (resp. after) the listening
+                                before or after the listening
                                 sockets/FIFOs are created and
-                                bound. The first token of the command
-                                line must be an absolute file name,
+                                bound, respectively. The first token of the command
+                                line must be an absolute filename,
                                 then followed by arguments for the
                                 process. Multiple command lines may be
                                 specified following the same scheme as
                                 <term><varname>ExecStopPre=</varname></term>
                                 <term><varname>ExecStopPost=</varname></term>
                                 <listitem><para>Additional commands
-                                that are executed before (resp. after)
+                                that are executed before or after
                                 the listening sockets/FIFOs are closed
-                                and removed. Multiple command lines
+                                and removed, respectively. Multiple command lines
                                 may be specified following the same
                                 scheme as used for
                                 <varname>ExecStartPre=</varname> of
                                 will be considered failed and be shut
                                 down again. All commands still running,
                                 will be terminated forcibly via
-                                SIGTERM, and after another delay of
-                                this time with SIGKILL. (See
-                                <option>KillMode=</option> below.)
+                                <constant>SIGTERM</constant>, and after another delay of
+                                this time with <constant>SIGKILL</constant>. (See
+                                <option>KillMode=</option> in <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
                                 Takes a unit-less value in seconds, or
                                 a time span value such as "5min
                                 20s". Pass 0 to disable the timeout
                                 logic. Defaults to
-                                60s.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>KillMode=</varname></term>
-                                <listitem><para>Specifies how
-                                processes of this socket unit shall be
-                                killed. One of
-                                <option>control-group</option>,
-                                <option>process</option>,
-                                <option>none</option>.</para>
-
-                                <para>This option is mostly equivalent
-                                to the <option>KillMode=</option>
-                                option of service files. See
-                                <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-                                for details.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>KillSignal=</varname></term>
-                                <listitem><para>Specifies which signal
-                                to use when killing a process of this
-                                socket. Defaults to SIGTERM.
-                                </para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>SendSIGKILL=</varname></term>
-                                <listitem><para>Specifies whether to
-                                send SIGKILL to remaining processes
-                                after a timeout, if the normal
-                                shutdown procedure left processes of
-                                the socket around. Takes a boolean
-                                value. Defaults to "yes".
-                                </para></listitem>
+                                90s.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                         </varlistentry>
 
                 </variablelist>
+
+                <para>Check
+                <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                and
+                <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                for more settings.</para>
+
         </refsect1>
 
         <refsect1>
                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-                          <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                          <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd.cgroup</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                  </para>
+
+                  <para>
+                          For more extensive descriptions see the "systemd for Developers" series:
+                          <ulink url="http://0pointer.de/blog/projects/socket-activation.html">Socket Activation</ulink>,
+                          <ulink url="http://0pointer.de/blog/projects/socket-activation2.html">Socket Activation, part II</ulink>,
+                          <ulink url="http://0pointer.de/blog/projects/inetd.html">Converting inetd Services</ulink>,
+                          <ulink url="http://0pointer.de/blog/projects/socket-activated-containers.html">Socket Activated Internet Services and OS Containers</ulink>.
                   </para>
         </refsect1>