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nixpkgs/doc/builders/special/fhs-environments.xml
Frederik Rietdijk 2b9713c281 doc: move fhs and mkShell under builders/special
In my opinion Functions should only contain pure functions. These are
both meant to provide derivations so I put them under Builders. Don't
know exactly *where* to put them so "special" it is...
2019-10-21 11:39:46 +02:00

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<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>