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| Copyright 2010 Lennart Poettering |
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| |
| <refentry id="systemd.socket"> |
| <refentryinfo> |
| <title>systemd.socket</title> |
| <productname>systemd</productname> |
| |
| <authorgroup> |
| <author> |
| <contrib>Developer</contrib> |
| <firstname>Lennart</firstname> |
| <surname>Poettering</surname> |
| <email>lennart@poettering.net</email> |
| </author> |
| </authorgroup> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>systemd.socket</refentrytitle> |
| <manvolnum>5</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>systemd.socket</refname> |
| <refpurpose>Socket unit configuration</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <para><filename><replaceable>socket</replaceable>.socket</filename></para> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para>A unit configuration file whose name ends in |
| <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> |
| |
| <para>This man page lists the configuration options |
| specific to this unit type. See |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for the common options of all unit configuration |
| files. The common configuration items are configured |
| in the generic [Unit] and [Install] sections. The |
| socket specific configuration options are configured |
| in the [Socket] section.</para> |
| |
| <para>Additional options are listed in |
| <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| which define the execution environment the |
| <option>ExecStartPre=</option>, |
| <option>ExecStartPost=</option>, |
| <option>ExecStopPre=</option> and |
| <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.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| which configure resource control settings for the |
| processes of the socket.</para> |
| |
| <para>For each socket file, a matching service file |
| must exist, describing the service to start on |
| incoming traffic on the socket (see |
| <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for more information about .service files). The name |
| of the .service unit is by default the same as the |
| name of the .socket unit, but can be altered with the |
| <option>Service=</option> option described below. |
| Depending on the setting of the <option>Accept=</option> |
| option described below, this .service unit must either |
| be named like the .socket unit, but with the suffix |
| replaced, unless overridden with |
| <option>Service=</option>; or it must be a template |
| unit named the same way. Example: a socket file |
| <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 file <filename>foo@.service</filename> must |
| exist from which services are instantiated for each |
| incoming connection.</para> |
| |
| <para>Unless <varname>DefaultDependencies=</varname> |
| is set to <option>false</option>, socket units will |
| implicitly have dependencies of type |
| <varname>Requires=</varname> and |
| <varname>After=</varname> on |
| <filename>sysinit.target</filename> as well as |
| dependencies of type <varname>Conflicts=</varname> and |
| <varname>Before=</varname> on |
| <filename>shutdown.target</filename>. These ensure |
| that socket units pull in basic system |
| initialization, and are terminated cleanly prior to |
| system shutdown. Only sockets involved with early |
| boot or late system shutdown should disable this |
| option.</para> |
| |
| <para>Socket units will have a |
| <varname>Before=</varname> dependency on the service |
| which they trigger added implicitly. No implicit |
| <varname>WantedBy=</varname> or |
| <varname>RequiredBy=</varname> dependency from the |
| socket to the service is added. This means that the |
| service may be started without the socket, in which |
| case it must be able to open sockets by itself. To |
| prevent this, an explicit <varname>Requires=</varname> |
| dependency may be added.</para> |
| |
| <para>Socket units may be used to implement on-demand |
| starting of services, as well as parallelized starting |
| of services. See the blog stories linked at the end |
| for an introduction.</para> |
| |
| <para>Note that the daemon software configured for |
| socket activation with socket units needs to be able |
| to accept sockets from systemd, either via systemd's |
| native socket passing interface (see |
| <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for details) or via the traditional |
| <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>-style |
| socket passing (i.e. sockets passed in via standard input and |
| output, using <varname>StandardInput=socket</varname> |
| in the service file).</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Options</title> |
| |
| <para>Socket files must include a [Socket] section, |
| which carries information about the socket or FIFO it |
| 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> |
| 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 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 |
| (<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 (<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 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 project='man-pages'><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 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 |
| 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. 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 <constant>AF_UNIX</constant> |
| sockets. <constant>SOCK_STREAM</constant> |
| (i.e. <varname>ListenStream=</varname>) |
| when used for IP sockets refers to TCP |
| 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 of 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>It is also possible to have more |
| than one socket unit for the same |
| service when using |
| <varname>Service=</varname>, and the |
| service will receive all the sockets |
| configured in all the socket units. |
| Sockets configured in one unit are |
| passed in the order of configuration, |
| but no ordering between socket units |
| is specified.</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 of whether it will be up and |
| running at any point. To deal with this, |
| it is recommended to set the |
| <varname>FreeBind=</varname> option |
| described below.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>ListenFIFO=</varname></term> |
| <listitem><para>Specifies a file |
| system FIFO to listen on. This expects |
| an absolute file system path as |
| 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>both</option> or |
| <option>ipv6-only</option>. Controls |
| the IPV6_V6ONLY socket option (see |
| <citerefentry><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details). If |
| <option>both</option>, IPv6 sockets |
| bound will be accessible via both IPv4 |
| and IPv6. If |
| <option>ipv6-only</option>, they will |
| be accessible via IPv6 only. If |
| <option>default</option> (which is the |
| default, surprise!), the system wide |
| default setting is used, as controlled |
| by |
| <filename>/proc/sys/net/ipv6/bindv6only</filename>, |
| which in turn defaults to the |
| equivalent of |
| <option>both</option>.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Backlog=</varname></term> |
| <listitem><para>Takes an unsigned |
| integer argument. Specifies the number |
| of connections to queue that have not |
| been accepted yet. This setting |
| matters only for stream and sequential |
| packet sockets. See |
| <citerefentry><refentrytitle>listen</refentrytitle><manvolnum>2</manvolnum></citerefentry> |
| for details. Defaults to SOMAXCONN |
| (128).</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>BindToDevice=</varname></term> |
| <listitem><para>Specifies a network |
| interface name to bind this socket |
| to. If set, traffic will only be |
| accepted from the specified network |
| interfaces. This controls the |
| SO_BINDTODEVICE socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details). If this option is used, |
| an automatic dependency from this |
| socket unit on the network interface |
| device unit |
| (<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| is created.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>SocketUser=</varname></term> |
| <term><varname>SocketGroup=</varname></term> |
| |
| <listitem><para>Takes a UNIX |
| user/group name. When specified, |
| all AF_UNIX sockets and FIFO nodes in |
| the file system are owned by the |
| specified user and group. If unset |
| (the default), the nodes are owned by |
| the root user/group (if run in system |
| context) or the invoking user/group |
| (if run in user context). If only a |
| user is specified but no group, then |
| the group is derived from the user's |
| default group.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>SocketMode=</varname></term> |
| <listitem><para>If listening on a file |
| system socket or FIFO, this option |
| specifies the file system access mode |
| used when creating the file |
| node. Takes an access mode in octal |
| notation. Defaults to |
| 0666.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>DirectoryMode=</varname></term> |
| <listitem><para>If listening on a file |
| system socket or FIFO, the parent |
| directories are automatically created |
| if needed. This option specifies the |
| file system access mode used when |
| creating these directories. Takes an |
| access mode in octal |
| notation. Defaults to |
| 0755.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Accept=</varname></term> |
| <listitem><para>Takes a boolean |
| argument. If true, a service instance |
| is spawned for each incoming |
| connection and only the connection |
| socket is passed to it. If false, all |
| listening sockets themselves are |
| passed to the started service unit, |
| and only one service unit is spawned |
| for all connections (also see |
| above). This value is ignored for |
| 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>. 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> |
| |
| <varlistentry> |
| <term><varname>MaxConnections=</varname></term> |
| <listitem><para>The maximum number of |
| connections to simultaneously run |
| services instances for, when |
| <option>Accept=true</option> is |
| set. If more concurrent connections |
| are coming in, they will be refused |
| until at least one existing connection |
| is terminated. This setting has no |
| effect on sockets configured with |
| <option>Accept=false</option> or datagram |
| sockets. Defaults to |
| 64.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>KeepAlive=</varname></term> |
| <listitem><para>Takes a boolean |
| argument. If true, the TCP/IP stack |
| will send a keep alive message after |
| 2h (depending on the configuration of |
| <filename>/proc/sys/net/ipv4/tcp_keepalive_time</filename>) |
| for all TCP streams accepted on this |
| socket. This controls the SO_KEEPALIVE |
| socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| and the <ulink |
| url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP |
| Keepalive HOWTO</ulink> for details.) |
| Defaults to |
| <option>false</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>KeepAliveTimeSec=</varname></term> |
| <listitem><para>Takes time (in seconds) as argument . The connection needs to remain |
| idle before TCP starts sending keepalive probes. This controls the TCP_KEEPIDLE |
| socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| and the <ulink |
| url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP |
| Keepalive HOWTO</ulink> for details.) |
| Defaults value is 7200 seconds (2 hours).</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>KeepAliveIntervalSec=</varname></term> |
| <listitem><para>Takes time (in seconds) as argument between individual keepalive probes, |
| if the socket option SO_KEEPALIVE has been set on this socket seconds as argument. |
| This controls the TCP_KEEPINTVL socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| and the <ulink |
| url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP |
| Keepalive HOWTO</ulink> for details.) |
| Defaults value is 75 seconds.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>KeepAliveProbes=</varname></term> |
| <listitem><para>Takes integer as argument. It's the number of unacknowledged probes to |
| send before considering the connection dead and notifying the application layer. |
| This controls the TCP_KEEPCNT socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| and the <ulink |
| url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP |
| Keepalive HOWTO</ulink> for details.) |
| Defaults value is 9.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>NoDelay=</varname></term> |
| <listitem><para>Takes a boolean |
| argument. TCP Nagle's algorithm works by combining a number of |
| small outgoing messages, and sending them all at once. |
| This controls the TCP_NODELAY socket option (see |
| <citerefentry><refentrytitle>tcp</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| Defaults to |
| <option>false</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Priority=</varname></term> |
| <listitem><para>Takes an integer |
| argument controlling the priority for |
| all traffic sent from this |
| socket. This controls the SO_PRIORITY |
| socket option (see |
| <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details.).</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>DeferAcceptSec=</varname></term> |
| |
| <listitem><para>Takes time (in |
| seconds) as argument. If set, the |
| listening process will be awakened |
| only when data arrives on the socket, |
| and not immediately when connection is |
| established. When this option is set, |
| the |
| <constant>TCP_DEFER_ACCEPT</constant> |
| socket option will be used (see |
| <citerefentry><refentrytitle>tcp</refentrytitle><manvolnum>7</manvolnum></citerefentry>), |
| and the kernel will ignore initial ACK |
| packets without any data. The argument |
| specifies the approximate amount of |
| time the kernel should wait for |
| incoming data before falling back to |
| the normal behaviour of honouring |
| empty ACK packets. This option is |
| beneficial for protocols where the |
| client sends the data first (e.g. |
| HTTP, in contrast to SMTP), because |
| the server process will not be woken |
| up unnecessarily before it can take |
| any action. |
| </para> |
| |
| <para>If the client also uses the |
| <constant>TCP_DEFER_ACCEPT</constant> |
| option, the latency of the initial |
| connection may be reduced, because the |
| kernel will send data in the final |
| packet establishing the connection |
| (the third packet in the "three-way |
| handshake").</para> |
| |
| <para>Disabled by default.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>ReceiveBuffer=</varname></term> |
| <term><varname>SendBuffer=</varname></term> |
| <listitem><para>Takes an integer |
| argument controlling the receive 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.). The usual suffixes K, |
| M, G are supported and are understood |
| to the base of 1024.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>IPTOS=</varname></term> |
| <listitem><para>Takes an integer |
| argument controlling the IP |
| Type-Of-Service field for packets |
| generated from this socket. This |
| controls the IP_TOS socket option (see |
| <citerefentry><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details.). Either a numeric string |
| or one of <option>low-delay</option>, |
| <option>throughput</option>, |
| <option>reliability</option> or |
| <option>low-cost</option> may be |
| specified.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>IPTTL=</varname></term> |
| <listitem><para>Takes an integer |
| argument controlling the IPv4 |
| Time-To-Live/IPv6 Hop-Count field for |
| packets generated from this |
| socket. This sets the |
| IP_TTL/IPV6_UNICAST_HOPS socket |
| options (see |
| <citerefentry><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| and |
| <citerefentry><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details.)</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Mark=</varname></term> |
| <listitem><para>Takes an integer |
| value. Controls the firewall mark of |
| packets generated by this socket. This |
| can be used in the firewall logic to |
| filter packets from this socket. This |
| sets the SO_MARK socket option. See |
| <citerefentry><refentrytitle>iptables</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for details.</para></listitem> |
| </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>SELinuxContextFromNet=</varname></term> |
| <listitem><para>Takes a boolean |
| argument. When true, systemd will attempt |
| to figure out the SELinux label used |
| for the instantiated service from the |
| information handed by the peer over the |
| network. Note that only the security |
| level is used from the information |
| provided by the peer. Other parts of |
| the resulting SELinux context originate |
| from either the target binary that is |
| effectively triggered by socket unit |
| or from the value of the |
| <varname>SELinuxContext=</varname> |
| option. This configuration option only |
| affects sockets with |
| <varname>Accept=</varname> mode set to |
| <literal>true</literal>. Also note that |
| this option is useful only when |
| MLS/MCS SELinux policy is |
| deployed. Defaults to |
| <literal>false</literal>. |
| </para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>PipeSize=</varname></term> |
| <listitem><para>Takes a size in |
| bytes. Controls the pipe buffer size |
| of FIFOs configured in this socket |
| unit. See |
| <citerefentry><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry> |
| for details. The usual suffixes K, M, |
| G are supported and are understood to |
| the base of 1024.</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 |
| be bound to non-local IP |
| addresses. This is useful to configure |
| sockets listening on specific IP |
| addresses before those IP addresses |
| are successfully configured on a |
| network interface. This sets the |
| IP_FREEBIND socket option. For |
| robustness reasons it is recommended |
| to use this option whenever you bind a |
| socket to a specific IP |
| address. Defaults to <option>false</option>.</para></listitem> |
| </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 |
| algorithm used by this socket. Should |
| be one of "westwood", "veno", "cubic", |
| "lp" or any other available algorithm |
| supported by the IP stack. This |
| setting applies only to stream |
| sockets.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>ExecStartPre=</varname></term> |
| <term><varname>ExecStartPost=</varname></term> |
| <listitem><para>Takes one or more |
| command lines, which are executed |
| before or after the listening |
| sockets/FIFOs are created and |
| 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 |
| used for |
| <varname>ExecStartPre=</varname> of |
| service unit files.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>ExecStopPre=</varname></term> |
| <term><varname>ExecStopPost=</varname></term> |
| <listitem><para>Additional commands |
| that are executed before or after |
| the listening sockets/FIFOs are closed |
| and removed, respectively. Multiple command lines |
| may be specified following the same |
| scheme as used for |
| <varname>ExecStartPre=</varname> of |
| service unit files.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>TimeoutSec=</varname></term> |
| <listitem><para>Configures the time to |
| wait for the commands specified in |
| <varname>ExecStartPre=</varname>, |
| <varname>ExecStartPost=</varname>, |
| <varname>ExecStopPre=</varname> and |
| <varname>ExecStopPost=</varname> to |
| finish. If a command does not exit |
| within the configured time, the socket |
| will be considered failed and be shut |
| down again. All commands still running |
| will be terminated forcibly via |
| <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 <literal>0</literal> to disable the timeout |
| logic. Defaults to <varname>DefaultTimeoutStartSec=</varname> from the |
| manager configuration file |
| (see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>). |
| </para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Service=</varname></term> |
| <listitem><para>Specifies the service |
| unit name to activate on incoming |
| traffic. This setting is only allowed |
| for sockets with |
| <varname>Accept=no</varname>. It |
| defaults to the service that bears the |
| same name as the socket (with the |
| suffix replaced). In most cases, it |
| should not be necessary to use this |
| option.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>RemoveOnStop=</varname></term> |
| <listitem><para>Takes a boolean |
| argument. If enabled, any file nodes |
| created by this socket unit are |
| removed when it is stopped. This |
| applies to AF_UNIX sockets in the file |
| system, POSIX message queues, FIFOs, |
| as well as any symlinks to |
| them configured with |
| <varname>Symlinks=</varname>. Normally, |
| it should not be necessary to use this |
| option, and is not recommended as |
| services might continue to run after |
| the socket unit has been terminated |
| and it should still be possible to |
| communicate with them via their file |
| system node. Defaults to |
| off.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>Symlinks=</varname></term> |
| <listitem><para>Takes a list of file |
| system paths. The specified paths will |
| be created as symlinks to the AF_UNIX |
| socket path or FIFO path of this |
| socket unit. If this setting is used, |
| only one AF_UNIX socket in the file |
| system or one FIFO may be configured |
| for the socket unit. Use this option |
| to manage one or more symlinked alias |
| names for a socket, binding their |
| lifecycle together. Defaults to the |
| empty list.</para></listitem> |
| </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> |
| <title>See Also</title> |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.resource-control</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> |
| |
| </refentry> |