man/systemd.socket.xml

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   9   Copyright 2010 Lennart Poettering
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  24
  25 <refentry id="systemd.socket">
  26         <refentryinfo>
  27                 <title>systemd.socket</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.socket</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.socket</refname>
  47                 <refpurpose>Socket unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename><replaceable>socket</replaceable>.socket</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <filename>.socket</filename> encodes information about
  59                 an IPC or network socket or a file system FIFO
  60                 controlled and supervised by systemd, for socket-based
  61                 activation.</para>
  62
  63                 <para>This man page lists the configuration options
  64                 specific to this unit type. See
  65                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  66                 for the common options of all unit configuration
  67                 files. The common configuration items are configured
  68                 in the generic [Unit] and [Install] sections. The
  69                 socket specific configuration options are configured
  70                 in the [Socket] section.</para>
  71
  72                 <para>Additional options are listed in
  73                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  74                 which define the execution environment the
  75                 <option>ExecStartPre=</option>,
  76                 <option>ExecStartPost=</option>,
  77                 <option>ExecStopPre=</option> and
  78                 <option>ExecStopPost=</option> commands are executed
  79                 in, and in
  80                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  81                 which define the way the processes are
  82                 terminated.</para>
  83
  84                 <para>For each socket file a matching service file
  85                 (see
  86                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  87                 for details) must exist, describing the service to
  88                 start on incoming traffic on the socket. Depending on
  89                 the setting of <option>Accept=</option> (see below),
  90                 this must either be named like the socket unit, but
  91                 with the suffix replaced; or it must be a template
  92                 file named the same way. Example: a socket file
  93                 <filename>foo.socket</filename> needs a matching
  94                 service <filename>foo.service</filename> if
  95                 <option>Accept=false</option> is set. If
  96                 <option>Accept=true</option> is set a service template
  97                 file <filename>foo@.service</filename> must exist from
  98                 which services are instantiated for each incoming
  99                 connection.</para>
 100
 101                 <para>Unless <varname>DefaultDependencies=</varname>
 102                 is set to <option>false</option>, socket units will
 103                 implicitly have dependencies of type
 104                 <varname>Requires=</varname> and
 105                 <varname>After=</varname> on
 106                 <filename>sysinit.target</filename> as well as
 107                 dependencies of type <varname>Conflicts=</varname> and
 108                 <varname>Before=</varname> on
 109                 <filename>shutdown.target</filename>. These ensure
 110                 that socket units pull in basic system
 111                 initialization, and are terminated cleanly prior to
 112                 system shutdown. Only sockets involved with early
 113                 boot or late system shutdown should disable this
 114                 option.</para>
 115
 116                 <para>Socket units may be used to implement on-demand
 117                 starting of services, as well as parallelized starting
 118                 of services.</para>
 119
 120                 <para>Note that the daemon software configured for
 121                 socket activation with socket units needs to be able
 122                 to accept sockets from systemd, either via systemd's
 123                 native socket passing interface (see
 124                 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 125                 for details) or via the traditional
 126                 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>-style
 127                 socket passing (i.e. sockets passed in via STDIN and
 128                 STDOUT, using <varname>StandardInput=socket</varname>
 129                 in the service file).</para>
 130         </refsect1>
 131
 132         <refsect1>
 133                 <title>Options</title>
 134
 135                 <para>Socket files must include a [Socket] section,
 136                 which carries information about the socket or FIFO it
 137                 supervises. A number of options that may be used in
 138                 this section are shared with other unit types. These
 139                 options are documented in
 140                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 141                 and
 142                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
 143                 options specific to the [Socket] section of socket
 144                 units are the following:</para>
 145
 146                 <variablelist class='unit-directives'>
 147                         <varlistentry>
 148                                 <term><varname>ListenStream=</varname></term>
 149                                 <term><varname>ListenDatagram=</varname></term>
 150                                 <term><varname>ListenSequentialPacket=</varname></term>
 151                                 <listitem><para>Specifies an address
 152                                 to listen on for a stream
 153                                 (SOCK_STREAM), datagram (SOCK_DGRAM),
 154                                 or sequential packet
 155                                 (SOCK_SEQPACKET) socket, respectively. The address
 156                                 can be written in various formats:</para>
 157
 158                                 <para>If the address starts with a
 159                                 slash (/), it is read as file system
 160                                 socket in the AF_UNIX socket
 161                                 family.</para>
 162
 163                                 <para>If the address starts with an
 164                                 at symbol (@) it is read as abstract
 165                                 namespace socket in the AF_UNIX
 166                                 family. The @ is replaced with a NUL
 167                                 character before binding. For details
 168                                 see
 169                                 <citerefentry><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 170
 171                                 <para>If the address string is a
 172                                 single number it is read as port
 173                                 number to listen on via
 174                                 IPv6. Depending on the value of
 175                                 <varname>BindIPv6Only=</varname> (see below) this
 176                                 might result in the service being
 177                                 available via both IPv6 and IPv4 (default) or
 178                                 just via IPv6.
 179                                 </para>
 180
 181                                 <para>If the address string is a
 182                                 string in the format v.w.x.y:z it is
 183                                 read as IPv4 specifier for listening
 184                                 on an address v.w.x.y on a port
 185                                 z.</para>
 186
 187                                 <para>If the address string is a
 188                                 string in the format [x]:y it is read
 189                                 as IPv6 address x on a port y. Note
 190                                 that this might make the service
 191                                 available via IPv4, too, depending on
 192                                 the <varname>BindIPv6Only=</varname>
 193                                 setting (see below).
 194                                 </para>
 195
 196                                 <para>Note that SOCK_SEQPACKET
 197                                 (i.e. <varname>ListenSequentialPacket=</varname>)
 198                                 is only available for AF_UNIX
 199                                 sockets. SOCK_STREAM
 200                                 (i.e. <varname>ListenStream=</varname>)
 201                                 when used for IP sockets refers to TCP
 202                                 sockets, SOCK_DGRAM
 203                                 (i.e. <varname>ListenDatagram=</varname>)
 204                                 to UDP.</para>
 205
 206                                 <para>These options may be specified
 207                                 more than once in which case incoming
 208                                 traffic on any of the sockets will
 209                                 trigger service activation, and all
 210                                 listed sockets will be passed to the
 211                                 service, regardless whether there is
 212                                 incoming traffic on them or not. If
 213                                 the empty string is assigned to any of
 214                                 these options, the list of addresses
 215                                 to listen on is reset, all prior uses
 216                                 of any of these options will have no
 217                                 effect.</para>
 218
 219                                 <para>If an IP address is used here,
 220                                 it is often desirable to listen on it
 221                                 before the interface it is configured
 222                                 on is up and running, and even
 223                                 regardless whether it will be up and
 224                                 running ever at all. To deal with this
 225                                 it is recommended to set the
 226                                 <varname>FreeBind=</varname> option
 227                                 described below.</para></listitem>
 228                         </varlistentry>
 229
 230                         <varlistentry>
 231                                 <term><varname>ListenFIFO=</varname></term>
 232                                 <listitem><para>Specifies a file
 233                                 system FIFO to listen on. This expects
 234                                 an absolute file system path as
 235                                 argument. Behavior otherwise is very
 236                                 similar to the
 237                                 <varname>ListenDatagram=</varname>
 238                                 directive above.</para></listitem>
 239                         </varlistentry>
 240
 241                         <varlistentry>
 242                                 <term><varname>ListenSpecial=</varname></term>
 243                                 <listitem><para>Specifies a special
 244                                 file in the file system to listen
 245                                 on. This expects an absolute file
 246                                 system path as argument. Behavior
 247                                 otherwise is very similar to the
 248                                 <varname>ListenFIFO=</varname>
 249                                 directive above. Use this to open
 250                                 character device nodes as well as
 251                                 special files in
 252                                 <filename>/proc</filename> and
 253                                 <filename>/sys</filename>.</para></listitem>
 254                         </varlistentry>
 255
 256                         <varlistentry>
 257                                 <term><varname>ListenNetlink=</varname></term>
 258                                 <listitem><para>Specifies a Netlink
 259                                 family to create a socket for to
 260                                 listen on. This expects a short string
 261                                 referring to the AF_NETLINK family
 262                                 name (such as <varname>audit</varname>
 263                                 or <varname>kobject-uevent</varname>)
 264                                 as argument, optionally suffixed by a
 265                                 whitespace followed by a multicast
 266                                 group integer. Behavior otherwise is
 267                                 very similar to the
 268                                 <varname>ListenDatagram=</varname>
 269                                 directive above.</para></listitem>
 270                         </varlistentry>
 271
 272                         <varlistentry>
 273                                 <term><varname>ListenMessageQueue=</varname></term>
 274                                 <listitem><para>Specifies a POSIX
 275                                 message queue name to listen on. This
 276                                 expects a valid message queue name
 277                                 (i.e. beginning with /). Behavior
 278                                 otherwise is very similar to the
 279                                 <varname>ListenFIFO=</varname>
 280                                 directive above. On Linux message
 281                                 queue descriptors are actually file
 282                                 descriptors and can be inherited
 283                                 between processes.</para></listitem>
 284                         </varlistentry>
 285
 286                         <varlistentry>
 287                                 <term><varname>BindIPv6Only=</varname></term>
 288                                 <listitem><para>Takes a one of
 289                                 <option>default</option>,
 290                                 <option>both</option> or
 291                                 <option>ipv6-only</option>. Controls
 292                                 the IPV6_V6ONLY socket option (see
 293                                 <citerefentry><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 294                                 for details). If
 295                                 <option>both</option>, IPv6 sockets
 296                                 bound will be accessible via both IPv4
 297                                 and IPv6. If
 298                                 <option>ipv6-only</option>, they will
 299                                 be accessible via IPv6 only. If
 300                                 <option>default</option> (which is the
 301                                 default, surprise!) the system wide
 302                                 default setting is used, as controlled
 303                                 by
 304                                 <filename>/proc/sys/net/ipv6/bindv6only</filename>,
 305                                 which in turn defaults to the
 306                                 equivalent of
 307                                 <option>both</option>.</para>
 308                                 </listitem>
 309                         </varlistentry>
 310
 311                         <varlistentry>
 312                                 <term><varname>Backlog=</varname></term>
 313                                 <listitem><para>Takes an unsigned
 314                                 integer argument. Specifies the number
 315                                 of connections to queue that have not
 316                                 been accepted yet. This setting
 317                                 matters only for stream and sequential
 318                                 packet sockets. See
 319                                 <citerefentry><refentrytitle>listen</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 320                                 for details. Defaults to SOMAXCONN
 321                                 (128).</para></listitem>
 322                         </varlistentry>
 323
 324                         <varlistentry>
 325                                 <term><varname>BindToDevice=</varname></term>
 326                                 <listitem><para>Specifies a network
 327                                 interface name to bind this socket
 328                                 to. If set traffic will only be
 329                                 accepted from the specified network
 330                                 interfaces. This controls the
 331                                 SO_BINDTODEVICE socket option (see
 332                                 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 333                                 for details). If this option is used,
 334                                 an automatic dependency from this
 335                                 socket unit on the network interface
 336                                 device unit
 337                                 (<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 338                                 is created.</para></listitem>
 339                         </varlistentry>
 340
 341                         <varlistentry>
 342                                 <term><varname>DirectoryMode=</varname></term>
 343                                 <listitem><para>If listening on a file
 344                                 system socket or FIFO, the parent
 345                                 directories are automatically created
 346                                 if needed. This option specifies the
 347                                 file system access mode used when
 348                                 creating these directories. Takes an
 349                                 access mode in octal
 350                                 notation. Defaults to
 351                                 0755.</para></listitem>
 352                         </varlistentry>
 353
 354                         <varlistentry>
 355                                 <term><varname>SocketMode=</varname></term>
 356                                 <listitem><para>If listening on a file
 357                                 system socket or FIFO, this option
 358                                 specifies the file system access mode
 359                                 used when creating the file
 360                                 node. Takes an access mode in octal
 361                                 notation. Defaults to
 362                                 0666.</para></listitem>
 363                         </varlistentry>
 364
 365                         <varlistentry>
 366                                 <term><varname>Accept=</varname></term>
 367                                 <listitem><para>Takes a boolean
 368                                 argument. If true, a service instance
 369                                 is spawned for each incoming
 370                                 connection and only the connection
 371                                 socket is passed to it. If false, all
 372                                 listening sockets themselves are
 373                                 passed to the started service unit,
 374                                 and only one service unit is spawned
 375                                 for all connections (also see
 376                                 above). This value is ignored for
 377                                 datagram sockets and FIFOs where
 378                                 a single service unit unconditionally
 379                                 handles all incoming traffic. Defaults
 380                                 to <option>false</option>. For
 381                                 performance reasons, it is recommended
 382                                 to write new daemons only in a way
 383                                 that is suitable for
 384                                 <option>Accept=false</option>. A daemon
 385                                 listening on an AF_UNIX socket may, but does not need to, call
 386                                 <citerefentry><refentrytitle>close</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 387                                 or
 388                                 <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 389                                 on the received socket before exiting. However,
 390                                 it must not unlink the socket from a
 391                                 filesystem. This option is mostly useful
 392                                 to allow daemons designed for usage with
 393                                 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 394                                 to work unmodified with systemd socket
 395                                 activation.</para></listitem>
 396                         </varlistentry>
 397
 398                         <varlistentry>
 399                                 <term><varname>MaxConnections=</varname></term>
 400                                 <listitem><para>The maximum number of
 401                                 connections to simultaneously run
 402                                 services instances for, when
 403                                 <option>Accept=true</option> is
 404                                 set. If more concurrent connections
 405                                 are coming in, they will be refused
 406                                 until at least one existing connection
 407                                 is terminated. This setting has no
 408                                 effect for sockets configured with
 409                                 <option>Accept=false</option> or datagram
 410                                 sockets. Defaults to
 411                                 64.</para></listitem>
 412                         </varlistentry>
 413
 414                         <varlistentry>
 415                                 <term><varname>KeepAlive=</varname></term>
 416                                 <listitem><para>Takes a boolean
 417                                 argument. If true, the TCP/IP stack
 418                                 will send a keep alive message after
 419                                 2h (depending on the configuration of
 420                                 <filename>/proc/sys/net/ipv4/tcp_keepalive_time</filename>)
 421                                 for all TCP streams accepted on this
 422                                 socket. This controls the SO_KEEPALIVE
 423                                 socket option (see
 424                                 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 425                                 and the <ulink
 426                                 url="http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/">TCP
 427                                 Keepalive HOWTO</ulink> for details.)
 428                                 Defaults to
 429                                 <option>false</option>.</para></listitem>
 430                         </varlistentry>
 431
 432                         <varlistentry>
 433                                 <term><varname>Priority=</varname></term>
 434                                 <listitem><para>Takes an integer
 435                                 argument controlling the priority for
 436                                 all traffic sent from this
 437                                 socket. This controls the SO_PRIORITY
 438                                 socket option (see
 439                                 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 440                                 for details.).</para></listitem>
 441                         </varlistentry>
 442
 443                         <varlistentry>
 444                                 <term><varname>ReceiveBuffer=</varname></term>
 445                                 <term><varname>SendBuffer=</varname></term>
 446                                 <listitem><para>Takes an integer
 447                                 argument controlling the receive
 448                                 or send buffer sizes of this
 449                                 socket, respectively. This controls the SO_RCVBUF
 450                                 and SO_SNDBUF socket options (see
 451                                 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 452                                 for details.).</para></listitem>
 453                         </varlistentry>
 454
 455                         <varlistentry>
 456                                 <term><varname>IPTOS=</varname></term>
 457                                 <listitem><para>Takes an integer
 458                                 argument controlling the IP
 459                                 Type-Of-Service field for packets
 460                                 generated from this socket. This
 461                                 controls the IP_TOS socket option (see
 462                                 <citerefentry><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 463                                 for details.). Either a numeric string
 464                                 or one of <option>low-delay</option>,
 465                                 <option>throughput</option>,
 466                                 <option>reliability</option> or
 467                                 <option>low-cost</option> may be
 468                                 specified.</para></listitem>
 469                         </varlistentry>
 470
 471                         <varlistentry>
 472                                 <term><varname>IPTTL=</varname></term>
 473                                 <listitem><para>Takes an integer
 474                                 argument controlling the IPv4
 475                                 Time-To-Live/IPv6 Hop-Count field for
 476                                 packets generated from this
 477                                 socket. This sets the
 478                                 IP_TTL/IPV6_UNICAST_HOPS socket
 479                                 options (see
 480                                 <citerefentry><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 481                                 and
 482                                 <citerefentry><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 483                                 for details.)</para></listitem>
 484                         </varlistentry>
 485
 486                         <varlistentry>
 487                                 <term><varname>Mark=</varname></term>
 488                                 <listitem><para>Takes an integer
 489                                 value. Controls the firewall mark of
 490                                 packets generated by this socket. This
 491                                 can be used in the firewall logic to
 492                                 filter packets from this socket. This
 493                                 sets the SO_MARK socket option. See
 494                                 <citerefentry><refentrytitle>iptables</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 495                                 for details.</para></listitem>
 496                         </varlistentry>
 497
 498                         <varlistentry>
 499                                 <term><varname>SmackLabel=</varname></term>
 500                                 <term><varname>SmackLabelIPIn=</varname></term>
 501                                 <term><varname>SmackLabelIPOut=</varname></term>
 502                                 <listitem><para>Takes a string
 503                                 value. Controls the extended
 504                                 attributes
 505                                 <literal>security.SMACK64</literal>,
 506                                 <literal>security.SMACK64IPIN</literal>
 507                                 and
 508                                 <literal>security.SMACK64IPOUT</literal>,
 509                                 respectively, i.e. the security label
 510                                 of the FIFO, or the security label for
 511                                 the incoming or outgoing connections
 512                                 of the socket, respectively.  See
 513                                 <ulink
 514                                 url="https://www.kernel.org/doc/Documentation/security/Smack.txt">Smack.txt</ulink>
 515                                 for details.</para></listitem>
 516                         </varlistentry>
 517
 518                         <varlistentry>
 519                                 <term><varname>PipeSize=</varname></term>
 520                                 <listitem><para>Takes an integer
 521                                 value. Controls the pipe buffer size
 522                                 of FIFOs configured in this socket
 523                                 unit.  See
 524                                 <citerefentry><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 525                                 for details.</para></listitem>
 526                         </varlistentry>
 527
 528                         <varlistentry>
 529                                 <term><varname>MessageQueueMaxMessages=</varname>,
 530                                 <varname>MessageQueueMessageSize=</varname></term>
 531                                 <listitem><para>These two settings
 532                                 take integer values and control the
 533                                 mq_maxmsg field or the mq_msgsize field, respectively, when
 534                                 creating the message queue. Note that
 535                                 either none or both of these variables
 536                                 need to be set. See
 537                                 <citerefentry><refentrytitle>mq_setattr</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 538                                 for details.</para></listitem>
 539                         </varlistentry>
 540
 541                         <varlistentry>
 542                                 <term><varname>FreeBind=</varname></term>
 543                                 <listitem><para>Takes a boolean
 544                                 value. Controls whether the socket can
 545                                 be bound to non-local IP
 546                                 addresses. This is useful to configure
 547                                 sockets listening on specific IP
 548                                 addresses before those IP addresses
 549                                 are successfully configured on a
 550                                 network interface. This sets the
 551                                 IP_FREEBIND socket option. For
 552                                 robustness reasons it is recommended
 553                                 to use this option whenever you bind a
 554                                 socket to a specific IP
 555                                 address. Defaults to <option>false</option>.</para></listitem>
 556                         </varlistentry>
 557
 558                         <varlistentry>
 559                                 <term><varname>Transparent=</varname></term>
 560                                 <listitem><para>Takes a boolean
 561                                 value. Controls the IP_TRANSPARENT
 562                                 socket option. Defaults to
 563                                 <option>false</option>.</para></listitem>
 564                         </varlistentry>
 565
 566                         <varlistentry>
 567                                 <term><varname>Broadcast=</varname></term>
 568                                 <listitem><para>Takes a boolean
 569                                 value. This controls the SO_BROADCAST
 570                                 socket option, which allows broadcast
 571                                 datagrams to be sent from this
 572                                 socket. Defaults to
 573                                 <option>false</option>.</para></listitem>
 574                         </varlistentry>
 575
 576                         <varlistentry>
 577                                 <term><varname>PassCredentials=</varname></term>
 578                                 <listitem><para>Takes a boolean
 579                                 value. This controls the SO_PASSCRED
 580                                 socket option, which allows AF_UNIX sockets to
 581                                 receive the credentials of the sending
 582                                 process in an ancillary message.
 583                                 Defaults to
 584                                 <option>false</option>.</para></listitem>
 585                         </varlistentry>
 586
 587                         <varlistentry>
 588                                 <term><varname>PassSecurity=</varname></term>
 589                                 <listitem><para>Takes a boolean
 590                                 value. This controls the SO_PASSSEC
 591                                 socket option, which allows AF_UNIX
 592                                 sockets to receive the security
 593                                 context of the sending process in an
 594                                 ancillary message.  Defaults to
 595                                 <option>false</option>.</para></listitem>
 596                         </varlistentry>
 597
 598                         <varlistentry>
 599                                 <term><varname>TCPCongestion=</varname></term>
 600                                 <listitem><para>Takes a string
 601                                 value. Controls the TCP congestion
 602                                 algorithm used by this socket. Should
 603                                 be one of "westwood", "veno", "cubic",
 604                                 "lp" or any other available algorithm
 605                                 supported by the IP stack. This
 606                                 setting applies only to stream
 607                                 sockets.</para></listitem>
 608                         </varlistentry>
 609
 610                         <varlistentry>
 611                                 <term><varname>ExecStartPre=</varname></term>
 612                                 <term><varname>ExecStartPost=</varname></term>
 613                                 <listitem><para>Takes one or more
 614                                 command lines, which are executed
 615                                 before or after the listening
 616                                 sockets/FIFOs are created and
 617                                 bound, respectively. The first token of the command
 618                                 line must be an absolute file name,
 619                                 then followed by arguments for the
 620                                 process. Multiple command lines may be
 621                                 specified following the same scheme as
 622                                 used for
 623                                 <varname>ExecStartPre=</varname> of
 624                                 service unit files.</para></listitem>
 625                         </varlistentry>
 626
 627                         <varlistentry>
 628                                 <term><varname>ExecStopPre=</varname></term>
 629                                 <term><varname>ExecStopPost=</varname></term>
 630                                 <listitem><para>Additional commands
 631                                 that are executed before or after
 632                                 the listening sockets/FIFOs are closed
 633                                 and removed, respectively. Multiple command lines
 634                                 may be specified following the same
 635                                 scheme as used for
 636                                 <varname>ExecStartPre=</varname> of
 637                                 service unit files.</para></listitem>
 638                         </varlistentry>
 639
 640                         <varlistentry>
 641                                 <term><varname>TimeoutSec=</varname></term>
 642                                 <listitem><para>Configures the time to
 643                                 wait for the commands specified in
 644                                 <varname>ExecStartPre=</varname>,
 645                                 <varname>ExecStartPost=</varname>,
 646                                 <varname>ExecStopPre=</varname> and
 647                                 <varname>ExecStopPost=</varname> to
 648                                 finish. If a command does not exit
 649                                 within the configured time, the socket
 650                                 will be considered failed and be shut
 651                                 down again. All commands still running,
 652                                 will be terminated forcibly via
 653                                 SIGTERM, and after another delay of
 654                                 this time with SIGKILL. (See
 655                                 <option>KillMode=</option> in <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
 656                                 Takes a unit-less value in seconds, or
 657                                 a time span value such as "5min
 658                                 20s". Pass 0 to disable the timeout
 659                                 logic. Defaults to
 660                                 90s.</para></listitem>
 661                         </varlistentry>
 662
 663                         <varlistentry>
 664                                 <term><varname>Service=</varname></term>
 665                                 <listitem><para>Specifies the service
 666                                 unit name to activate on incoming
 667                                 traffic. This defaults to the service
 668                                 that bears the same name as the socket
 669                                 (ignoring the different suffixes). In
 670                                 most cases it should not be necessary
 671                                 to use this option.</para></listitem>
 672                         </varlistentry>
 673
 674                 </variablelist>
 675
 676                 <para>Check
 677                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 678                 and
 679                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 680                 for more settings.</para>
 681
 682         </refsect1>
 683
 684         <refsect1>
 685                   <title>See Also</title>
 686                   <para>
 687                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 688                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 689                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 690                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 691                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 692                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 693                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 694                   </para>
 695
 696                   <para>
 697                           For more extensive descriptions see the "Systemd for Developers" series:
 698                           <ulink url="http://0pointer.de/blog/projects/socket-activation.html">Socket Activation</ulink>,
 699                           <ulink url="http://0pointer.de/blog/projects/socket-activation2.html">Socket Activation, part II</ulink>,
 700                           <ulink url="http://0pointer.de/blog/projects/inetd.html">Converting inetd Services</ulink>,
 701                           <ulink url="http://0pointer.de/blog/projects/socket-activated-containers.html">Socket Activated Internet Services and OS Containers</ulink>.
 702                   </para>
 703         </refsect1>
 704
 705 </refentry>