nixpkgs/nixos/doc/manual/administration/rebooting.xml

<chapter 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-rebooting">
 <title>Rebooting and Shutting Down</title>
 <para>
  The system can be shut down (and automatically powered off) by doing:
<screen>
# shutdown
</screen>
  This is equivalent to running <command>systemctl poweroff</command>.
 </para>
 <para>
  To reboot the system, run
<screen>
# reboot
</screen>
  which is equivalent to <command>systemctl reboot</command>. Alternatively,
  you can quickly reboot the system using <literal>kexec</literal>, which
  bypasses the BIOS by directly loading the new kernel into memory:
<screen>
# systemctl kexec
</screen>
 </para>
 <para>
  The machine can be suspended to RAM (if supported) using <command>systemctl
  suspend</command>, and suspended to disk using <command>systemctl
  hibernate</command>.
 </para>
 <para>
  These commands can be run by any user who is logged in locally, i.e. on a
  virtual console or in X11; otherwise, the user is asked for authentication.
 </para>
</chapter>