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Merge pull request #34534 from keszybz/man-exitrd

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Formally document exitrds
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Mike Yuan 2024-09-30 21:02:04 +02:00 committed by GitHub
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6
TODO
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@ -1374,12 +1374,6 @@ Features:
CapabilityQuintet we already have. (This likely allows us to drop libcap
dep in the base OS image)
* add concept for "exitrd" as inverse of "initrd", that we can transition to at
shutdown, and has similar security semantics. This should then take the place
of dracut's shutdown logic. Should probably support sysexts too. Care needs
to be taken that the resulting logic ends up in RAM, i.e. is copied out of
on-disk storage.
* userdbd: implement an additional varlink service socket that provides the
host user db in restricted form, then allow this to be bind mounted into
sandboxed environments that want the host database in minimal form. All

17
man/bootup.xml
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@ -47,9 +47,9 @@
necessary file systems and spawning all configured services.</para>
<para>On shutdown, the system manager stops all services, unmounts all non-busy file systems (detaching
the storage technologies backing them), and then (optionally) jumps into the exitrd, which is backed by
tmpfs, and unmounts/detaches the remaining file systems, including the real root. As a last step,
the system is powered down.</para>
the storage technologies backing them), and then (optionally) jumps into the exitrd. The exitrd is backed
by tmpfs and unmounts/detaches the remaining file systems, including the real root. As a last step, the
system is powered down.</para>
<para>Additional information about the system boot process may be
found in
@ -343,6 +343,17 @@ systemd-reboot.service | | | |
shutdown phase described above.</para>
</refsect1>
<refsect1>
<title>The exitrd</title>
<para>The "exitrd" is a concept symmetrical to the initrd. When the system manager is shutting down and
<filename>/run/initramfs/shutdown</filename> exists, it will switch root to
<filename>/run/initramfs/</filename> and execute <filename>/shutdown</filename>. This program runs from
the tmpfs mounted on <filename>/run/</filename>, so it can unmount the old root file system and perform
additional steps, for example dismantle complex storage or perform additional logging about the shutdown.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">

20
man/os-release.xml
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@ -53,9 +53,9 @@
precedence over <filename>/usr/lib/os-release</filename>.
Applications should check for the former, and exclusively use its
data if it exists, and only fall back to
<filename>/usr/lib/os-release</filename> if it is missing.
Applications should not read data from both files at the same
time. <filename>/usr/lib/os-release</filename> is the recommended
<filename>/usr/lib/os-release</filename> if that is missing.
Applications should not combine the data from both files.
<filename>/usr/lib/os-release</filename> is the recommended
place to store OS release information as part of vendor trees.
<filename>/etc/os-release</filename> should be a relative symlink
to <filename>/usr/lib/os-release</filename>, to provide
@ -88,10 +88,10 @@
<refsect2>
<title><filename>/etc/initrd-release</filename></title>
<para>In the <ulink
url="https://docs.kernel.org/admin-guide/initrd.html">initrd</ulink>,
<para>In the <ulink url="https://docs.kernel.org/admin-guide/initrd.html">initrd</ulink>
and exitrd,
<filename>/etc/initrd-release</filename> plays the same role as <filename>os-release</filename> in the
main system. Additionally, the presence of that file means that the system is in the initrd phase.
main system. Additionally, the presence of that file means that the system is in the initrd/exitrd phase.
<filename>/etc/os-release</filename> should be symlinked to <filename>/etc/initrd-release</filename>
(or vice versa), so programs that only look for <filename>/etc/os-release</filename> (as described
above) work correctly.</para>
@ -594,10 +594,10 @@
<listitem><para>Takes a space-separated list of one or more of the strings
<literal>system</literal>, <literal>initrd</literal> and <literal>portable</literal>. This field is
only supported in <filename>extension-release.d/</filename> files and indicates what environments
the system extension is applicable to: i.e. to regular systems, to initrds, or to portable service
images. If unspecified, <literal>SYSEXT_SCOPE=system portable</literal> is implied, i.e. any system
extension without this field is applicable to regular systems and to portable service environments,
but not to initrd environments.</para>
the system extension is applicable to: i.e. to regular systems, to initrds and exitrds, or to
portable service images. If not specified, <literal>SYSEXT_SCOPE=system portable</literal> is
implied, i.e. any system extension without this field is applicable to regular systems and to
portable service environments, but not to initrd/exitrd environments.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
</varlistentry>