nixpkgs/doc/functions/fhs-environments.xml

<section xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         xml:id="sec-fhs-environments">
  <title>buildFHSUserEnv</title>

  <para>
   <function>buildFHSUserEnv</function> provides a way to build and run
   FHS-compatible lightweight sandboxes. It creates an isolated root with bound
   <filename>/nix/store</filename>, so its footprint in terms of disk space
   needed is quite small. This allows one to run software which is hard or
   unfeasible to patch for NixOS -- 3rd-party source trees with FHS
   assumptions, games distributed as tarballs, software with integrity checking
   and/or external self-updated binaries. It uses Linux namespaces feature to
   create temporary lightweight environments which are destroyed after all
   child processes exit, without root user rights requirement. Accepted
   arguments are:
  </para>

  <variablelist>
   <varlistentry>
    <term>
     <literal>name</literal>
    </term>
    <listitem>
     <para>
      Environment name.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>targetPkgs</literal>
    </term>
    <listitem>
     <para>
      Packages to be installed for the main host's architecture (i.e. x86_64 on
      x86_64 installations). Along with libraries binaries are also installed.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>multiPkgs</literal>
    </term>
    <listitem>
     <para>
      Packages to be installed for all architectures supported by a host (i.e.
      i686 and x86_64 on x86_64 installations). Only libraries are installed by
      default.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>extraBuildCommands</literal>
    </term>
    <listitem>
     <para>
      Additional commands to be executed for finalizing the directory
      structure.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>extraBuildCommandsMulti</literal>
    </term>
    <listitem>
     <para>
      Like <literal>extraBuildCommands</literal>, but executed only on multilib
      architectures.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>extraOutputsToInstall</literal>
    </term>
    <listitem>
     <para>
      Additional derivation outputs to be linked for both target and
      multi-architecture packages.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>extraInstallCommands</literal>
    </term>
    <listitem>
     <para>
      Additional commands to be executed for finalizing the derivation with
      runner script.
     </para>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term>
     <literal>runScript</literal>
    </term>
    <listitem>
     <para>
      A command that would be executed inside the sandbox and passed all the
      command line arguments. It defaults to <literal>bash</literal>.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <para>
   One can create a simple environment using a <literal>shell.nix</literal>
   like that:
  </para>

<programlisting><![CDATA[
{ pkgs ? import <nixpkgs> {} }:

(pkgs.buildFHSUserEnv {
  name = "simple-x11-env";
  targetPkgs = pkgs: (with pkgs;
    [ udev
      alsaLib
    ]) ++ (with pkgs.xorg;
    [ libX11
      libXcursor
      libXrandr
    ]);
  multiPkgs = pkgs: (with pkgs;
    [ udev
      alsaLib
    ]);
  runScript = "bash";
}).env
]]></programlisting>

  <para>
   Running <literal>nix-shell</literal> would then drop you into a shell with
   these libraries and binaries available. You can use this to run
   closed-source applications which expect FHS structure without hassles:
   simply change <literal>runScript</literal> to the application path, e.g.
   <filename>./bin/start.sh</filename> -- relative paths are supported.
  </para>
 </section>