nixpkgs/nixos/doc/manual/configuration/profiles/clone-config.xml

<section xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="sec-profile-clone-config">
 <title>Clone Config</title>

 <para>
  This profile is used in installer images. It provides an editable configuration.nix that imports all the modules that were also used when creating the image in the first place. As a result it allows users to edit and rebuild the live-system.
 </para>

 <para>
  On images where the installation media also becomes an installation target, copying over <literal>configuration.nix</literal> should be disabled by setting <literal>installer.cloneConfig</literal> to <literal>false</literal>. For example, this is done in <literal>sd-image-aarch64.nix</literal>.
 </para>
</section>