keyMap = mkOption {
        type = types.nullOr types.string;
        default = null;
        description = ''
          Which layout to use in the GRUB menu.

          <note><para>This does not affect the core image (for example the LUKS
          password prompt).</para></note>

          Acceptables values are:
          <itemizedlist>
          <listitem><para><litteral>null</litteral>: leave GRUB default</para></listitem>
          <listitem><para><litteral>"console"</litteral>: use the value of <option>i18n.consoleKeyMap</option></para></listitem>
          <listitem><para><litteral>"x"</litteral>: use the layout configured for the X server</para></listitem>
          <listitem><para>another string, like <literal>"fr"</literal>.</para></listitem>
          </itemizedlist>
        '';
      };