systemd/man/sysctl.d.xml
Tom Gundersen 12b42c7667 man: revert dynamic paths for split-usr setups
This did not really work out as we had hoped. Trying to do this upstream
introduced several problems that probably makes it better suited as a
downstream patch after all. At any rate, it is not releaseable in the
current state, so we at least need to revert this before the release.

 * by adjusting the path to binaries, but not do the same thing to the
   search path we end up with inconsistent man-pages. Adjusting the search
   path too would be quite messy, and it is not at all obvious that this is
   worth the effort, but at any rate it would have to be done before we
   could ship this.

 * this means that distributed man-pages does not make sense as they depend
   on config options, and for better or worse we are still distributing
   man pages, so that is something that definitely needs sorting out before
   we could ship with this patch.

 * we have long held that split-usr is only minimally supported in order
   to boot, and something we hope will eventually go away. So before we start
   adding even more magic/effort in order to make this work nicely, we should
   probably question if it makes sense at all.
2015-06-18 19:47:44 +02:00

172 lines
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XML

<?xml version="1.0"?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="sysctl.d"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sysctl.d</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sysctl.d</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>sysctl.d</refname>
<refpurpose>Configure kernel parameters at boot</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/etc/sysctl.d/*.conf</filename></para>
<para><filename>/run/sysctl.d/*.conf</filename></para>
<para><filename>/usr/lib/sysctl.d/*.conf</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>At boot,
<citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
reads configuration files from the above directories to configure
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
kernel parameters.</para>
</refsect1>
<refsect1>
<title>Configuration Format</title>
<para>The configuration files contain a list of variable
assignments, separated by newlines. Empty lines and lines whose
first non-whitespace character is <literal>#</literal> or
<literal>;</literal> are ignored.</para>
<para>Note that either <literal>/</literal> or
<literal>.</literal> may be used as separators within sysctl
variable names. If the first separator is a slash, remaining
slashes and dots are left intact. If the first separator is a dot,
dots and slashes are interchanged.
<literal>kernel.domainname=foo</literal> and
<literal>kernel/domainname=foo</literal> are equivalent and will
cause <literal>foo</literal> to be written to
<filename>/proc/sys/kernel/domainname</filename>. Either
<literal>net.ipv4.conf.enp3s0/200.forwarding</literal> or
<literal>net/ipv4/conf/enp3s0.200/forwarding</literal> may be used
to refer to
<filename>/proc/sys/net/ipv4/conf/enp3s0.200/forwarding</filename>.
</para>
<para>The settings configured with <filename>sysctl.d</filename>
files will be applied early on boot. The network
interface-specific options will also be applied individually for
each network interface as it shows up in the system. (More
specifically, <filename>net.ipv4.conf.*</filename>,
<filename>net.ipv6.conf.*</filename>,
<filename>net.ipv4.neigh.*</filename> and
<filename>net.ipv6.neigh.*</filename>).</para>
<para>Many sysctl parameters only become available when certain
kernel modules are loaded. Modules are usually loaded on demand,
e.g. when certain hardware is plugged in or network brought up.
This means that
<citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
which runs during early boot will not configure such parameters if
they become available after it has run. To set such parameters, it
is recommended to add an
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
rule to set those parameters when they become available.
Alternatively, a slightly simpler and less efficient option is to
add the module to
<citerefentry><refentrytitle>modules-load.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
causing it to be loaded statically before sysctl settings are
applied (see example below).</para>
</refsect1>
<xi:include href="standard-conf.xml" xpointer="confd" />
<refsect1>
<title>Examples</title>
<example>
<title>Set kernel YP domain name</title>
<para><filename>/etc/sysctl.d/domain-name.conf</filename>:
</para>
<programlisting>kernel.domainname=example.com</programlisting>
</example>
<example>
<title>Disable packet filter on bridged packets (method one)</title>
<para><filename>/etc/udev/rules.d/99-bridge.rules</filename>:
</para>
<programlisting>ACTION=="add", SUBSYSTEM=="module", KERNEL=="bridge", RUN+="/usr/lib/systemd/systemd-sysctl --prefix=/net/bridge"
</programlisting>
<para><filename>/etc/sysctl.d/bridge.conf</filename>:
</para>
<programlisting>net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
</programlisting>
</example>
<example>
<title>Disable packet filter on bridged packets (method two)</title>
<para><filename>/etc/modules-load.d/bridge.conf</filename>:
</para>
<programlisting>bridge</programlisting>
<para><filename>/etc/sysctl.d/bridge.conf</filename>:
</para>
<programlisting>net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>modprobe</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>