X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=man%2Fsysctl.d.xml;h=3002ebd0fdc13bcbca3206793e0e7fac2ea4a5c9;hp=20f2e24820e53e2d38225a5e5593c526a1a12dc4;hb=1b600437bac3c0676cc72f589909c4cbfe38ba10;hpb=95f77929d8d94480015cd7383a5504cf9ebf2fa5

diff --git a/man/sysctl.d.xml b/man/sysctl.d.xml
index 20f2e2482..3002ebd0f 100644
--- a/man/sysctl.d.xml
+++ b/man/sysctl.d.xml
@@ -7,16 +7,16 @@
   Copyright 2011 Lennart Poettering
 
   systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
   (at your option) any later version.
 
   systemd is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  General Public License for more details.
+  Lesser General Public License for more details.
 
-  You should have received a copy of the GNU General Public License
+  You should have received a copy of the GNU Lesser General Public License
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 -->
 <refentry id="sysctl.d">
@@ -54,60 +54,136 @@
         <refsect1>
                 <title>Description</title>
 
-		<para><command>systemd</command> uses configuration
-		files from the above directories to configure
-		<citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
-		kernel parameters during boot.</para>
+                <para>At boot,
+                <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                reads configuration files from the above directories
+                to configure
+                <citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                kernel parameters.</para>
         </refsect1>
 
         <refsect1>
-		<title>Configuration Format</title>
+                <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 # or ; are ignored.</para>
-
-                <para>Note that both / and . are accepted as label
-                separators within sysctl variable
-                names. <literal>kernel.domainname=foo</literal> and
-                <literal>kernel/domainname=foo</literal> hence are
-                entirely equivalent.</para>
+                <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>Each configuration file shall be named in the
-                style of <filename>&lt;program&gt;.conf</filename>.
-                Files in <filename>/run/</filename> override files
-                with the same name in <filename>/usr/lib/</filename>.
-                Files in <filename>/etc</filename> override files with
-                the same name in <filename>/run/</filename> and
-                <filename>/usr/lib/</filename>. Packages should
-                install their configuration files in
+                style of <filename><replaceable>program</replaceable>.conf</filename>.
+                Files in <filename>/etc/</filename> override files
+                with the same name in <filename>/usr/lib/</filename>
+                and <filename>/run/</filename>.  Files in
+                <filename>/run/</filename> override files with the same
+                name in <filename>/usr/lib/</filename>. Packages
+                should install their configuration files in
                 <filename>/usr/lib/</filename>. Files in
                 <filename>/etc/</filename> are reserved for the local
                 administrator, who may use this logic to override the
-                configuration installed by vendor packages. All
-                configuration files are sorted by their name in
-                alphabetical order, regardless in which of the
-                directories they reside, to guarantee that a specific
-                configuration file takes precedence over another file
-                with an alphabetically earlier name, if both files
-                contain the same variable setting.</para>
+                configuration files installed by vendor packages. All
+                configuration files are sorted by their filename in
+                lexicographic order, regardless of which of the
+                directories they reside in. If multiple files specify the
+                same variable name, the entry in the file with the
+                lexicographically latest name will be applied. It is
+                recommended to prefix all filenames with a two-digit
+                number and a dash, to simplify the ordering of the
+                files.</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>If the administrator wants to disable a
-                configuration file supplied by the vendor the
+                configuration file supplied by the vendor, the
                 recommended way is to place a symlink to
                 <filename>/dev/null</filename> in
-                <filename>/etc/sysctl.d</filename> carrying with the
-                same name.</para>
+                <filename>/etc/sysctl.d/</filename> bearing the
+                same 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>
 
         <refsect1>
-                <title>Example</title>
+                <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>/etc/sysctl.d/domain-name.conf example:</title>
+                        <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># Set kernel YP domain name
-kernel.domainname=example.com</programlisting>
+                        <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>
 
@@ -115,8 +191,11 @@ kernel.domainname=example.com</programlisting>
                 <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><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                        <citerefentry><refentrytitle>modprobe</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                 </para>
         </refsect1>