nixpkgs/nixos/doc/manual/preface.xml

<preface xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xml:id="preface">
 <title>Preface</title>
 <para>
  This manual describes how to install, use and extend NixOS, a Linux
  distribution based on the purely functional package management system
  <link xlink:href="https://nixos.org/nix">Nix</link>, that is composed
  using modules and packages defined in the
  <link xlink:href="https://nixos.org/nixpkgs">Nixpkgs</link> project.
 </para>
 <para>
  Additional information regarding the Nix package manager and the Nixpkgs
  project can be found in respectively the
  <link xlink:href="https://nixos.org/nix/manual">Nix manual</link> and the
  <link xlink:href="https://nixos.org/nixpkgs/manual">Nixpkgs manual</link>.
 </para>
 <para>
  If you encounter problems, please report them on the
  <literal
   xlink:href="https://discourse.nixos.org">Discourse</literal> or
  on the <link
   xlink:href="irc://irc.libera.chat/#nixos">
  <literal>#nixos</literal> channel on Libera.Chat</link>, or
  consider
  <link
   xlink:href="#chap-contributing">
   contributing to this manual</link>. Bugs should be
  reported in
  <link
   xlink:href="https://github.com/NixOS/nixpkgs/issues">NixOS’
  GitHub issue tracker</link>.
 </para>
 <note>
  <para>
   Commands prefixed with <literal>#</literal> have to be run as root, either
   requiring to login as root user or temporarily switching to it using
   <literal>sudo</literal> for example.
  </para>
 </note>
</preface>