nixos manual: add grub option to avoid #21830

Close #22659. vcunat edited this slightly.

Changed files
+4
nixos
doc
manual
configuration
+4
nixos/doc/manual/configuration/luks-file-systems.xml
···
fileSystems."/".device = "/dev/mapper/crypted";
</programlisting>
+
Should grub be used as bootloader, and <filename>/boot</filename> is located
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on an encrypted partition, it is necessary to add the following grub option:
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<programlisting>boot.loader.grub.enableCryptodisk = true;</programlisting>
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</para>
</section>