nixpkgs/nixos/doc/manual/from_md/installation/installing-behind-a-proxy.section.xml

<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-installing-behind-proxy">
  <title>Installing behind a proxy</title>
  <para>
    To install NixOS behind a proxy, do the following before running
    <literal>nixos-install</literal>.
  </para>
  <orderedlist numeration="arabic">
    <listitem>
      <para>
        Update proxy configuration in
        <literal>/mnt/etc/nixos/configuration.nix</literal> to keep the
        internet accessible after reboot.
      </para>
      <programlisting language="bash">
networking.proxy.default = &quot;http://user:password@proxy:port/&quot;;
networking.proxy.noProxy = &quot;127.0.0.1,localhost,internal.domain&quot;;
</programlisting>
    </listitem>
    <listitem>
      <para>
        Setup the proxy environment variables in the shell where you are
        running <literal>nixos-install</literal>.
      </para>
      <programlisting>
# proxy_url=&quot;http://user:password@proxy:port/&quot;
# export http_proxy=&quot;$proxy_url&quot;
# export HTTP_PROXY=&quot;$proxy_url&quot;
# export https_proxy=&quot;$proxy_url&quot;
# export HTTPS_PROXY=&quot;$proxy_url&quot;
</programlisting>
    </listitem>
  </orderedlist>
  <note>
    <para>
      If you are switching networks with different proxy configurations,
      use the <literal>specialisation</literal> option in
      <literal>configuration.nix</literal> to switch proxies at runtime.
      Refer to <xref linkend="ch-options" /> for more information.
    </para>
  </note>
</section>