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>
in the [Socket] section.</para>
<para>Additional options are listed in
- <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+ <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>ExecStoptPost=</option> commands are executed
+ in, and in
+ <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ which define the way the processes are
+ terminated.</para>
<para>For each socket file a matching service file
(see
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details) must exist, describing the service to
start on incoming traffic on the socket. Depending on
- the setting of <option>Accept=</option> (see below)
+ the setting of <option>Accept=</option> (see below),
this must either be named like the socket unit, but
with the suffix replaced; or it must be a template
file named the same way. Example: a socket file
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 may be used to implement on-demand
- starting of services as well as parallelized starting
+ starting of services, as well as parallelized starting
of services.</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 STDIN and
+ STDOUT, using <varname>StandardInput=socket</varname>
+ in the service file).</para>
</refsect1>
<refsect1>
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>
family.</para>
<para>If the address starts with an
- ampersand (@) it is read as abstract
+ at symbol (@) it is read as abstract
namespace socket in the AF_UNIX
family. The @ is replaced with a NUL
character before binding. For details
regardless whether there is incoming
traffic on them or not.</para>
- <para>If an IP address is used here it
+ <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
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. Behaviour
+ 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 AF_NETLINK 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. Behaviour 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 /). Behaviour
+ 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
interfaces. This controls the
SO_BINDTODEVICE socket option (see
<citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- for details). If this option is used
+ for details). If this option is used,
an automatic dependency from this
socket unit on the network interface
device unit
<varlistentry>
<term><varname>DirectoryMode=</varname></term>
<listitem><para>If listening on a file
- system socket of FIFO the parent
+ system socket of FIFO, the parent
directories are automatically created
if needed. This option specifies the
file system access mode used when
- creating these directories. Defaults
- to 0755.</para></listitem>
+ creating these directories. Takes an
+ access mode in octal
+ notation. Defaults to
+ 0755.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SocketMode=</varname></term>
<listitem><para>If listening on a file
- system socket of FIFO this option
+ system socket of FIFO, this option
specifies the file system access mode
used when creating the file
- node. Defaults to
+ node. Takes an access mode in octal
+ notation. Defaults to
0666.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Accept=</varname></term>
<listitem><para>Takes a boolean
- argument. If true a service instance
+ argument. If true, a service instance
is spawned for each incoming
connection and only the connection
- socket is passed to it. If false all
+ 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
- unconditionally a single service unit
+ a single service unit unconditionally
handles all incoming traffic. Defaults
to <option>false</option>. For
- performance reasons it is recommended
+ 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>
- to work unmodified with system socket
+ <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ to work unmodified with systemd socket
activation.</para></listitem>
</varlistentry>
services instances for, when
<option>Accept=true</option> is
set. If more concurrent connections
- are coming in they will be refused,
+ are coming in, they will be refused
until at least one existing connection
is terminated. This setting has no
effect for sockets configured with
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 resp. mq_msgsize field 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
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 AF_UNIX 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 AF_UNIX
+ 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 a command line
- that is executed before (resp. after)
- the listening sockets/FIFOs are created and
+ <listitem><para>Takes one or more
+ command lines, which are executed
+ before (resp. after) the listening
+ sockets/FIFOs are created and
bound. The first token of the command
line must be an absolute file name,
then followed by arguments for the
- process. If specified more than once,
- all commands are executed one after
- the other, serially. Use of these
- settings is optional.</para></listitem>
+ 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>
<listitem><para>Additional commands
that are executed before (resp. after)
the listening sockets/FIFOs are closed
- and removed. If specified more than
- once, all commands are executed one
- after the other, serially. Use of
- these settings is
- optional.</para></listitem>
+ and removed. Multiple command lines
+ may be specified following the same
+ scheme as used for
+ <varname>ExecStartPre=</varname> of
+ service unit files.</para></listitem>
</varlistentry>
<varlistentry>
<varname>ExecStartPost=</varname>,
<varname>ExecStopPre=</varname> and
<varname>ExecStopPost=</varname> to
- finish. If a comand does not exit
- within the configured time the socket
+ 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
+ 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.)
+ <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>
+ 90s.</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-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>
+ <term><varname>Service=</varname></term>
+ <listitem><para>Specifies the service
+ unit name to activate on incoming
+ traffic. This defaults to the service
+ that bears the same name as the socket
+ (ignoring the different suffixes). In
+ most cases it should not be necessary
+ to use this option.</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>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<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.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff