</refnamediv>
<refsynopsisdiv>
- <para><filename>systemd.socket</filename></para>
+ <para><filename><replaceable>socket</replaceable>.socket</filename></para>
</refsynopsisdiv>
<refsect1>
<term><varname>ListenSequentialPacket=</varname></term>
<listitem><para>Specifies an address
to listen on for a stream
- (SOCK_STREAM), datagram (SOCK_DGRAM),
+ (<constant>SOCK_STREAM</constant>), datagram (<constant>SOCK_DGRAM</constant>),
or sequential packet
- (SOCK_SEQPACKET) socket, respectively. The address
+ (<constant>SOCK_SEQPACKET</constant>) socket, respectively. The address
can be written in various formats:</para>
<para>If the address starts with a
slash (/), it is read as file system
- socket in the AF_UNIX socket
+ socket in the <constant>AF_UNIX</constant> socket
family.</para>
<para>If the address starts with an
at symbol (@) it is read as abstract
- namespace socket in the AF_UNIX
+ namespace socket in the <constant>AF_UNIX</constant>
family. The @ is replaced with a NUL
character before binding. For details
see
setting (see below).
</para>
- <para>Note that SOCK_SEQPACKET
+ <para>Note that <constant>SOCK_SEQPACKET</constant>
(i.e. <varname>ListenSequentialPacket=</varname>)
- is only available for AF_UNIX
- sockets. SOCK_STREAM
+ 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, SOCK_DGRAM
+ sockets, <constant>SOCK_DGRAM</constant>
(i.e. <varname>ListenDatagram=</varname>)
to UDP.</para>
<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
+ 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
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
+ 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>. This
- option is mostly useful to allow
- daemons designed for usage with
- <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <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>
are coming in, they will be refused
until at least one existing connection
is terminated. This setting has no
- effect for sockets configured with
+ effect on sockets configured with
<option>Accept=false</option> or datagram
sockets. Defaults to
64.</para></listitem>
respectively, i.e. the security label
of the FIFO, or the security label for
the incoming or outgoing connections
- of the socket, respectively. See
+ of the socket, respectively. See
<ulink
url="https://www.kernel.org/doc/Documentation/security/Smack.txt">Smack.txt</ulink>
for details.</para></listitem>
<listitem><para>Takes an integer
value. Controls the pipe buffer size
of FIFOs configured in this socket
- unit. See
+ unit. See
<citerefentry><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for details.</para></listitem>
</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
+ socket option, which allows <constant>AF_UNIX</constant> sockets to
receive the credentials of the sending
process in an ancillary message.
Defaults to
<term><varname>PassSecurity=</varname></term>
<listitem><para>Takes a boolean
value. This controls the SO_PASSSEC
- socket option, which allows AF_UNIX
+ socket option, which allows <constant>AF_UNIX</constant>
sockets to receive the security
context of the sending process in an
- ancillary message. Defaults to
+ ancillary message. Defaults to
<option>false</option>.</para></listitem>
</varlistentry>
before or after the listening
sockets/FIFOs are created and
bound, respectively. The first token of the command
- line must be an absolute file name,
+ line must be an absolute filename,
then followed by arguments for the
process. Multiple command lines may be
specified following the same scheme as
<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>
~ianmdlvl / elogind.git / blobdiff