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man: rework documentation of kernel-install config

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Variables read by kernel-install and those exported by it were described
without any clear separation. So in particular it was pretty hard to answer
a question like "what variables can be set in install.conf". The in- and
out-variables are now split into two separate subsections.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2022-07-01 10:52:12 +02:00
parent 5e193bef89
commit f5f5047ff1
1 changed files with 90 additions and 65 deletions
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83
man/kernel-install.xml
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@ -144,6 +144,7 @@
<refsect1>
<title>The <varname>$BOOT</varname> partition</title>
<para>The partition where the kernels and <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
Loader Specification</ulink> snippets are located is called <varname>$BOOT</varname>.
<command>kernel-install</command> determines the location of this partition by checking
@ -173,45 +174,45 @@
<refsect1>
<title>Environment variables</title>
<para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be set for
the plugins. They may output additional logs in this case.</para>
<refsect2>
<title>Environment variables exported for plugins</title>
<para>If <varname>$MACHINE_ID</varname> is set and not empty when <command>kernel-install</command> is
invoked, it will be used as <replaceable>MACHINE-ID</replaceable>, overriding any automatic detection
attempts. The value must be a valid machine ID (32 hexadecimal characters).</para>
<para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be
exported for plugins. They may output additional logs in this case.</para>
<para><varname>$KERNEL_INSTALL_MACHINE_ID</varname> is set for the plugins to the desired
<replaceable>MACHINE-ID</replaceable> to use. It's always a 128bit ID, and typically the ID from
<filename>/etc/machine-id</filename> or the one passed in via <varname>$MACHINE_ID</varname>. (If no
machine ID was specified via these methods it might be generated randomly by
<command>kernel-install</command>, in which case it only applies to this invocation.)</para>
<para><varname>$KERNEL_INSTALL_MACHINE_ID</varname> is set for the plugins to the desired machine-id to
use. It's always a 128-bit ID. Normally it's read from <filename>/etc/machine-id</filename>, but it can
also be overriden via <varname>$MACHINE_ID</varname> (see below). If not specified via these methods a
fallback value will generated by <command>kernel-install</command>, and used only for a single
invocation.</para>
<para><varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> is set for the plugins to the desired entry "token"
to use. It's an identifier that shall be used to identify the local installation, and is often the
machine ID, i.e. same as <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, but might also be a different
type of identifier, for example a fixed string or the <varname>ID=</varname>,
<para><varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> is set for the plugins to the desired entry
"token" to use. It's an identifier that shall be used to identify the local installation, and is often
the machine ID, i.e. same as <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, but might also be a
different type of identifier, for example a fixed string or the <varname>ID=</varname>,
<varname>IMAGE_ID=</varname> values from <filename>/etc/os-release</filename>. The string passed here
will be used to name Boot Loader Specification entries, or the directories the kernel image and initial
RAM disk images are placed into. Note that while oftentimes
<varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> and <varname>$KERNEL_INSTALL_MACHINE_ID</varname> are set
to the same value, the latter is guaranteed to be a valid 32 character ID in lowercase hexadecimals while
the former can be any short string. The entry token to use is read from
<filename>/etc/kernel/entry-token</filename>, if it exists. Otherwise a few possible candidates below the
<varname>$BOOT</varname> are searched for Boot Loader Specification Type 1 entry directories, and if
found the entry token is derived from that. If that is not successful the machine ID is used as
fallback.</para>
RAM disk images are placed into.</para>
<para>Note that while <varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> and
<varname>$KERNEL_INSTALL_MACHINE_ID</varname> are often set to the same value, the latter is guaranteed
to be a valid 32 character ID in lowercase hexadecimals while the former can be any short string. The
entry token to use is read from <filename>/etc/kernel/entry-token</filename>, if it exists. Otherwise a
few possible candidates below <varname>$BOOT</varname> are checked for Boot Loader Specification Type 1
entry directories, and if found the entry token is derived from that. If that is not successful,
<varname>$KERNEL_INSTALL_MACHINE_ID</varname> is used as fallback.</para>
<para><varname>$KERNEL_INSTALL_BOOT_ROOT</varname> is set for the plugins to the absolute path of the
root directory (mount point, usually) of the hierarchy where boot loader entries, kernel images, and
associated resources should be placed. This usually is the path where the XBOOTLDR partition or the ESP
(EFI System Partition) are mounted, and also conceptually referred to as <varname>$BOOT</varname>. Can be
overridden by setting <varname>$BOOT_ROOT</varname>.</para>
(EFI System Partition) are mounted, and also conceptually referred to as <varname>$BOOT</varname>. Can
be overridden by setting <varname>$BOOT_ROOT</varname> (see below).</para>
<para><varname>$KERNEL_INSTALL_LAYOUT=bls|other|...</varname> is set for the plugins to specify the
installation layout. Defaults to <option>bls</option> if
<filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable></filename> exists, or <option>other</option>
otherwise. Additional layout names may be defined by convention. If a plugin uses a special layout, it's
encouraged to declare its own layout name and configure <varname>layout=</varname> in
otherwise. Additional layout names may be defined by convention. If a plugin uses a special layout,
it's encouraged to declare its own layout name and configure <varname>layout=</varname> in
<filename>install.conf</filename> upon initial installation. The following values are currently
understood:</para>
@ -239,11 +240,25 @@
<para><varname>$KERNEL_INSTALL_INITRD_GENERATOR</varname> is set for plugins to select the initrd
generator. This may be configured as <varname>initrd_generator=</varname> in
<filename>install.conf</filename>. See below.</para>
<filename>install.conf</filename>, see below.</para>
<para><varname>$KERNEL_INSTALL_STAGING_AREA</varname> is set for plugins to a path to a directory.
Plugins may drop files in that directory, and they will be installed as part of the loader entry, based
on the file name and extension.</para>
</refsect2>
<refsect2>
<title>Environment variables understood by <command>kernel-install</command></title>
<para><varname>$MACHINE_ID</varname> can be set for <command>kernel-install</command> to override
<varname>$KERNEL_INSTALL_MACHINE_ID</varname>, the machine ID.</para>
<para><varname>$BOOT_ROOT</varname> can be set for <command>kernel-install</command> to override
<varname>$KERNEL_INSTALL_BOOT_ROOT</varname>, the installation location for boot entries.</para>
<para>Those variables may also be set in <filename>install.conf</filename>. Variables set in the
environment take precedence over the values specified in the config file.</para>
</refsect2>
</refsect1>
<refsect1>
@ -327,8 +342,18 @@
<listitem>
<para>Configuration options for <command>kernel-install</command>, as a series of
<varname>KEY=</varname><replaceable>VALUE</replaceable> assignments, compatible with shell
syntax. This currently supports two keys: <varname>layout=</varname> and
<varname>initrd_generator=</varname>, for details see the Environment variables section above.</para>
syntax, following the same rules as described in
<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
<filename>/etc/kernel/install.conf</filename> will be read if present, and
<filename>/usr/lib/kernel/install.conf</filename> otherwise. This file is optional.
</para>
<para>Currently, the following keys are supported:
<varname>MACHINE_ID=</varname>,
<varname>BOOT_ROOT=</varname>,
<varname>layout=</varname>,
<varname>initrd_generator=</varname>.
See the Environment variables section above for details.</para>
</listitem>
</varlistentry>
</variablelist>