nixpkgs/nixos/doc/manual/from_md/configuration/ssh.section.xml

<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-ssh">
  <title>Secure Shell Access</title>
  <para>
    Secure shell (SSH) access to your machine can be enabled by setting:
  </para>
  <programlisting language="bash">
services.openssh.enable = true;
</programlisting>
  <para>
    By default, root logins using a password are disallowed. They can be
    disabled entirely by setting
    <xref linkend="opt-services.openssh.permitRootLogin" /> to
    <literal>&quot;no&quot;</literal>.
  </para>
  <para>
    You can declaratively specify authorised RSA/DSA public keys for a
    user as follows:
  </para>
  <programlisting language="bash">
users.users.alice.openssh.authorizedKeys.keys =
  [ &quot;ssh-dss AAAAB3NzaC1kc3MAAACBAPIkGWVEt4...&quot; ];
</programlisting>
</section>