mirror of
https://github.com/systemd/systemd.git
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77 lines
3.7 KiB
XML
77 lines
3.7 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="systemd-boot-system-token.service" conditional='ENABLE_EFI'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-boot-system-token.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-boot-system-token.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-boot-system-token.service</refname>
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<refpurpose>Generate an initial boot loader system token and random seed</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-boot-system-token.service</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-boot-system-token.service</filename> is a system service that automatically
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generates a 'system token' to store in an EFI variable in the system's NVRAM and a random seed to store
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on the EFI System Partition ESP on disk. The boot loader may then combine these two randomized data
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fields by cryptographic hashing, and pass it to the OS it boots as initialization seed for its entropy
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pool. The random seed stored in the ESP is refreshed on each reboot ensuring that multiple subsequent
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boots will boot with different seeds. The 'system token' is generated randomly once, and then
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persistently stored in the system's EFI variable storage.</para>
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<para>The <filename>systemd-boot-system-token.service</filename> unit invokes the <command>bootctl
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random-seed</command> command, which updates the random seed in the ESP, and initializes the 'system
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token' if it's not initialized yet. The service is conditionalized so that it is run only when all of the
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below apply:</para>
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<itemizedlist>
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<listitem><para>A boot loader is used that implements the <ulink
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url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink> (which defines the 'system
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token' concept).</para></listitem>
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<listitem><para>Either a 'system token' was not set yet, or the boot loader has not passed the OS a
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random seed yet (and thus most likely has been missing the random seed file in the
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ESP).</para></listitem>
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<listitem><para>The system is not running in a VM environment. This case is explicitly excluded since
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on VM environments the ESP backing storage and EFI variable storage is typically not physically
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separated and hence booting the same OS image in multiple instances would replicate both, thus reusing
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the same random seed and 'system token' among all instances, which defeats its purpose. Note that it's
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still possible to use boot loader random seed provisioning in this mode, but the automatic logic
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implemented by this service has no effect then, and the user instead has to manually invoke the
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<command>bootctl random-seed</command> acknowledging these restrictions.</para></listitem>
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</itemizedlist>
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<para>For further details see
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<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, regarding
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the command this service invokes.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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