<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-<!-- SPDX-License-Identifier: LGPL-2.1+ -->
-<refentry id="systemd-random-seed.service" conditional='ENABLE_RANDOMSEED'>
+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+<refentry id="systemd-random-seed.service" conditional='ENABLE_RANDOMSEED'
+ xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-random-seed.service</title>
<refnamediv>
<refname>systemd-random-seed.service</refname>
<refname>systemd-random-seed</refname>
- <refpurpose>Load and save the system random seed at boot and shutdown</refpurpose>
+ <refpurpose>Load and save the OS system random seed at boot and shutdown</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-random-seed.service</filename></para>
- <para><filename>/usr/lib/systemd/random-seed</filename></para>
+ <para><filename>/usr/lib/systemd/systemd-random-seed</filename></para>
</refsynopsisdiv>
<refsect1>
into the kernel entropy pool during boot and saves it at shutdown. See
<citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for
details. By default, no entropy is credited when the random seed is written into the kernel entropy pool,
- but this may be changed with <varname>$SYSTEMD_RANDOM_SEED_CREDIT</varname>, see below. On disk the random
+ but this may be changed with <varname>$SYSTEMD_RANDOM_SEED_CREDIT</varname>, see below. On disk the random
seed is stored in <filename>/var/lib/systemd/random-seed</filename>.</para>
<para>Note that this service runs relatively late during the early boot phase, i.e. generally after the
- initial RAM disk (initrd) completed its work, and the <filename>/var/</filename> file system has been
- mounted writable. Many system services require entropy much earlier than this — this service is hence of
- limited use for complex system. It is recommended to use a boot loader that can pass an initial random
- seed to the kernel to ensure that entropy is available from earliest boot on, for example
+ initrd phase has finished and the <filename>/var/</filename> file system has been mounted. Many system
+ services require entropy much earlier than this — this service is hence of limited use for complex
+ system. It is recommended to use a boot loader that can pass an initial random seed to the kernel to
+ ensure that entropy is available from earliest boot on, for example
<citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>, with
its <command>bootctl random-seed</command> functionality.</para>
- <para>When loading the random seed from disk its file is immediately updated with a new seed retrieved
+ <para>When loading the random seed from disk, the file is immediately updated with a new seed retrieved
from the kernel, in order to ensure no two boots operate with the same random seed. This new seed is
retrieved synchronously from the kernel, which means the service will not complete start-up until the
random pool is fully initialized. On entropy-starved systems this may take a while. This functionality is
thus — if otherwise entropy-starved — generate the same or at least guessable random seed streams. As a
safety precaution crediting entropy is thus disabled by default. It is recommended to remove the random
seed from OS images intended for replication on multiple systems, in which case it is safe to enable
- entropy crediting, see below.</para>
+ entropy crediting, see below. Also see <ulink url="https://systemd.io/BUILDING_IMAGES">Safely Building
+ Images</ulink>.</para>
<para>See <ulink url="https://systemd.io/RANDOM_SEEDS">Random Seeds</ulink> for further
information.</para>
a boolean parameter or the special string <literal>force</literal>. Defaults to false, in which case
no entropy is credited. If true, entropy is credited if the random seed file and system state pass
various superficial concisistency checks. If set to <literal>force</literal> entropy is credited,
- regardless of these checks, as long as the random seed file exists.</para></listitem>
+ regardless of these checks, as long as the random seed file exists.</para>
+
+ <xi:include href="version-info.xml" xpointer="v243"/></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>4</manvolnum></citerefentry>
- </para>
+ <para><simplelist type="inline">
+ <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>4</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>systemd-boot-random-seed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
+ </simplelist></para>
</refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff