<orderedlist>
<listitem><para>Close all open file
- descriptors except STDIN, STDOUT,
- STDERR (i.e. the first three file
+ descriptors except standard input, output,
+ and error (i.e. the first three file
descriptors 0, 1, 2). This ensures
that no accidentally passed file
descriptor stays around in the daemon
with a fallback of iterating from file
descriptor 3 to the value returned by
<function>getrlimit()</function> for
- RLIMIT_NOFILE.</para></listitem>
+ <constant>RLIMIT_NOFILE</constant>.
+ </para></listitem>
<listitem><para>Reset all signal
handlers to their default. This is
best done by iterating through the
available signals up to the limit of
- _NSIG and resetting them to
+ <constant>_NSIG</constant> and resetting them to
<constant>SIG_DFL</constant>.</para></listitem>
<listitem><para>Reset the signal mask
<listitem><para>In the daemon process,
connect <filename>/dev/null</filename>
- to STDIN, STDOUT,
- STDERR.</para></listitem>
+ to standard input, output, and error.
+ </para></listitem>
<listitem><para>In the daemon process,
reset the umask to 0, so that the file
write the daemon PID (as returned by
<function>getpid()</function>) to a
PID file, for example
- <filename>/var/run/foobar.pid</filename>
+ <filename>/run/foobar.pid</filename>
(for a hypothetical daemon "foobar")
to ensure that the daemon cannot be
started more than once. This must be
it is verified at the same time that
the PID previously stored in the PID
file no longer exists or belongs to a
- foreign process. Commonly, some kind of
- file locking is employed to implement
- this logic.</para></listitem>
+ foreign process.</para></listitem>
<listitem><para>In the daemon process,
drop privileges, if possible and
service.</para>
<para>Note that new-style init systems
- guarantee execution of daemon processes in
- a clean process context: it is guaranteed that
+ guarantee execution of daemon processes in a
+ clean process context: it is guaranteed that
the environment block is sanitized, that the
signal handlers and mask is reset and that no
left-over file descriptors are passed. Daemons
- will be executed in their own session, and
- STDIN/STDOUT/STDERR connected to
+ will be executed in their own session, with
+ standard input/output/error connected to
<filename>/dev/null</filename> unless
- otherwise configured. The umask is reset.</para>
+ otherwise configured. The umask is reset.
+ </para>
<para>It is recommended for new-style daemons
to implement the following:</para>
detect service errors and problems. It
is recommended to follow the exit code
scheme as defined in the <ulink
- url="http://refspecs.freestandards.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB
+ url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB
recommendations for SysV init
scripts</ulink>.</para></listitem>
interface.</para></listitem>
<listitem><para>Instead of using the
- <function>syslog()</function> call to log directly to the
- system syslog service, a new-style daemon may
- choose to simply log to STDERR via
- <function>fprintf()</function>, which is then forwarded to
- syslog by the init system. If log
- priorities are necessary, these can be
- encoded by prefixing individual log
- lines with strings like "<4>"
- (for log priority 4 "WARNING" in the
- syslog priority scheme), following a
- similar style as the Linux kernel's
- <function>printk()</function> priority system. In fact,
- using this style of logging also
- enables the init system to optionally
- direct all application logging to the
- kernel log buffer (kmsg), as
- accessible via
- <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. This
- kind of logging may be enabled by
- setting
- <varname>StandardError=syslog</varname>
- in the service unit file. For details,
- see
+ <function>syslog()</function> call to
+ log directly to the system syslog
+ service, a new-style daemon may choose
+ to simply log to standard error via
+ <function>fprintf()</function>, which
+ is then forwarded to syslog by the
+ init system. If log levels are
+ necessary, these can be encoded by
+ prefixing individual log lines with
+ strings like <literal><4></literal> (for log
+ level 4 "WARNING" in the syslog
+ priority scheme), following a similar
+ style as the Linux kernel's
+ <function>printk()</function> level
+ system. For details, see
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
<para>These recommendations are similar but
not identical to the <ulink
- url="http://developer.apple.com/mac/library/documentation/MacOSX/Conceptual/BPSystemStartup/Articles/LaunchOnDemandDaemons.html#//apple_ref/doc/uid/TP40001762-104738">Apple
+ url="https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html">Apple
MacOS X Daemon Requirements</ulink>.</para>
</refsect2>
exclusively on boot (and manually by the
administrator) via SysV init scripts, as
detailed in the <ulink
- url="http://refspecs.freestandards.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB
+ url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB
Linux Standard Base Core
Specification</ulink>. This method of
activation is supported ubiquitously on Linux
on a network interface, because network
sockets shall be bound to the
address. However, an alternative to implement
- this is by utilizing the Linux IP_FREEBIND
+ this is by utilizing the Linux <constant>IP_FREEBIND</constant>
socket option, as accessible via
<varname>FreeBind=yes</varname> in systemd
socket files (see
boot.</para>
<para>Packages using
- <citerefentry><refentrytitle>autoconf</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ <citerefentry project='die-net'><refentrytitle>autoconf</refentrytitle><manvolnum>1</manvolnum></citerefentry>
are recommended to use a configure script
excerpt like the following to determine the
unit installation path during source
<programlisting>PKG_PROG_PKG_CONFIG
AC_ARG_WITH([systemdsystemunitdir],
- AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files]),,
+ [AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files])],,
[with_systemdsystemunitdir=auto])
AS_IF([test "x$with_systemdsystemunitdir" = "xyes" -o "x$with_systemdsystemunitdir" = "xauto"], [
def_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd)
[AS_IF([test "x$with_systemdsystemunitdir" = "xyes"],
[AC_MSG_ERROR([systemd support requested but pkg-config unable to query systemd package])])
with_systemdsystemunitdir=no],
- [with_systemdsystemunitdir=$def_systemdsystemunitdir])])
+ [with_systemdsystemunitdir="$def_systemdsystemunitdir"])])
AS_IF([test "x$with_systemdsystemunitdir" != "xno"],
[AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])])
-AM_CONDITIONAL(HAVE_SYSTEMD, [test "x$with_systemdsystemunitdir" != "xno"])</programlisting>
+AM_CONDITIONAL([HAVE_SYSTEMD], [test "x$with_systemdsystemunitdir" != "xno"])</programlisting>
<para>This snippet allows automatic
installation of the unit files on systemd
work, it is recommended to add the following
to the top-level <filename>Makefile.am</filename>
file in
- <citerefentry><refentrytitle>automake</refentrytitle><manvolnum>1</manvolnum></citerefentry>-based
+ <citerefentry project='die-net'><refentrytitle>automake</refentrytitle><manvolnum>1</manvolnum></citerefentry>-based
projects:</para>
<programlisting>DISTCHECK_CONFIGURE_FLAGS = \
endif</programlisting>
<para>In the
- <citerefentry><refentrytitle>rpm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ <citerefentry project='die-net'><refentrytitle>rpm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
<filename>.spec</filename> file, use snippets
like the following to enable/disable the
service during
</orderedlist>
</refsect1>
+ <refsect1>
+ <title>Placing Daemon Data</title>
+
+ <para>It is recommended to follow the general
+ guidelines for placing package files, as discussed in
+ <citerefentry><refentrytitle>file-hierarchy</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
+ </refsect1>
+
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>file-hierarchy</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff