which configure resource control settings for the
processes of the socket.</para>
- <para>For each socket file a matching service file
- (see
+ <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 details) must exist, describing the service to
- start on incoming traffic on the socket. Depending on
- 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
+ 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>
+ <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
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.</para>
+ 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
<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>
+ socket passing (i.e. sockets passed in via standard input and
+ output, using <varname>StandardInput=socket</varname>
in the service file).</para>
</refsect1>
replaced with a
<constant>NUL</constant> character
before binding. For details, see
- <citerefentry><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
+ <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
traffic on any of the sockets will
trigger service activation, and all
listed sockets will be passed to the
- service, regardless whether there is
+ 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
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 whether it will be up and
- running ever at all. To deal with this
+ 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>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>
+ <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>
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
<option>false</option>.</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
<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
+ 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.).</para></listitem>
+ for details.). The usual suffixes K,
+ M, G are supported and are understood
+ to the base of 1024.</para></listitem>
</varlistentry>
<varlistentry>
<varlistentry>
<term><varname>PipeSize=</varname></term>
- <listitem><para>Takes an integer
- value. Controls the pipe buffer size
+ <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.</para></listitem>
+ for details. The usual suffixes K, M,
+ G are supported and are understood to
+ the base of 1024.</para></listitem>
</varlistentry>
<varlistentry>
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
<constant>SIGTERM</constant>, and after another delay of
this time with <constant>SIGKILL</constant>. (See
<option>KillMode=</option> in <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
Takes a unit-less value in seconds, or
a time span value such as "5min
- 20s". Pass 0 to disable the timeout
- logic. Defaults to <varname>TimeoutStartSec=</varname> in
- manager configuration file.</para></listitem>
+ 20s". Pass <literal>0</literal> to disable the timeout
+ logic. Defaults to <varname>DefaultTimeoutStartSec=</varname> from the
+ manager configuration file
+ (see <citerefentry><refentrytitle>systemd-systemd.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 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>
+ 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>
~ianmdlvl / elogind.git / blobdiff