+ <para>Each configuration file shall be named in the
+ 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 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>If the administrator wants to disable a
+ 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> 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>