which configure resource control settings for the
processes of the socket.</para>
- <para>For each socket file a matching service file
+ <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
+ name of the .socket unit, but can be altered with the
<option>Service=</option> option described below.
- Depending on the setting of <option>Accept=</option>
+ 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
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 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 introduction.</para>
+ for an introduction.</para>
<para>Note that the daemon software configured for
socket activation with socket units needs to be able
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
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
+ 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>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 interger 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
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
+ 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> from the
- 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>
<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
+ 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
~ianmdlvl / elogind.git / blobdiff