mirror of
https://github.com/ilyakooo0/nixpkgs.git
synced 2024-11-11 15:27:20 +03:00
295 lines
9.5 KiB
XML
295 lines
9.5 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
|
||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
xml:id="chap-functions">
|
||
|
||
<title>Functions reference</title>
|
||
|
||
<para>
|
||
The nixpkgs repository has several utility functions to manipulate Nix expressions.
|
||
</para>
|
||
|
||
<section xml:id="sec-pkgs-overridePackages">
|
||
<title>pkgs.overridePackages</title>
|
||
|
||
<para>
|
||
This function inside the nixpkgs expression (<varname>pkgs</varname>)
|
||
can be used to override the set of packages itself.
|
||
</para>
|
||
<para>
|
||
Warning: this function is expensive and must not be used from within
|
||
the nixpkgs repository.
|
||
</para>
|
||
<para>
|
||
Example usage:
|
||
|
||
<programlisting>let
|
||
pkgs = import <nixpkgs> {};
|
||
newpkgs = pkgs.overridePackages (self: super: {
|
||
foo = super.foo.override { ... };
|
||
};
|
||
in ...</programlisting>
|
||
</para>
|
||
|
||
<para>
|
||
The resulting <varname>newpkgs</varname> will have the new <varname>foo</varname>
|
||
expression, and all other expressions depending on <varname>foo</varname> will also
|
||
use the new <varname>foo</varname> expression.
|
||
</para>
|
||
|
||
<para>
|
||
The behavior of this function is similar to <link
|
||
linkend="sec-modify-via-packageOverrides">config.packageOverrides</link>.
|
||
</para>
|
||
|
||
<para>
|
||
The <varname>self</varname> parameter refers to the final package set with the
|
||
applied overrides. Using this parameter may lead to infinite recursion if not
|
||
used consciously.
|
||
</para>
|
||
|
||
<para>
|
||
The <varname>super</varname> parameter refers to the old package set.
|
||
It's equivalent to <varname>pkgs</varname> in the above example.
|
||
</para>
|
||
|
||
</section>
|
||
|
||
<section xml:id="sec-pkg-override">
|
||
<title><pkg>.override</title>
|
||
|
||
<para>
|
||
The function <varname>override</varname> is usually available for all the
|
||
derivations in the nixpkgs expression (<varname>pkgs</varname>).
|
||
</para>
|
||
<para>
|
||
It is used to override the arguments passed to a function.
|
||
</para>
|
||
<para>
|
||
Example usages:
|
||
|
||
<programlisting>pkgs.foo.override { arg1 = val1; arg2 = val2; ... }</programlisting>
|
||
<programlisting>pkgs.overridePackages (self: super: {
|
||
foo = super.foo.override { barSupport = true ; };
|
||
})</programlisting>
|
||
<programlisting>mypkg = pkgs.callPackage ./mypkg.nix {
|
||
mydep = pkgs.mydep.override { ... };
|
||
})</programlisting>
|
||
</para>
|
||
|
||
<para>
|
||
In the first example, <varname>pkgs.foo</varname> is the result of a function call
|
||
with some default arguments, usually a derivation.
|
||
Using <varname>pkgs.foo.override</varname> will call the same function with
|
||
the given new arguments.
|
||
</para>
|
||
|
||
</section>
|
||
|
||
<section xml:id="sec-pkg-overrideDerivation">
|
||
<title><pkg>.overrideDerivation</title>
|
||
|
||
<warning>
|
||
<para>Do not use this function in Nixpkgs. Because it breaks
|
||
package abstraction and doesn’t provide error checking for
|
||
function arguments, it is only intended for ad-hoc customisation
|
||
(such as in <filename>~/.nixpkgs/config.nix</filename>).</para>
|
||
</warning>
|
||
|
||
<para>
|
||
The function <varname>overrideDerivation</varname> is usually available for all the
|
||
derivations in the nixpkgs expression (<varname>pkgs</varname>).
|
||
</para>
|
||
<para>
|
||
It is used to create a new derivation by overriding the attributes of
|
||
the original derivation according to the given function.
|
||
</para>
|
||
|
||
<para>
|
||
Example usage:
|
||
|
||
<programlisting>mySed = pkgs.gnused.overrideDerivation (oldAttrs: {
|
||
name = "sed-4.2.2-pre";
|
||
src = fetchurl {
|
||
url = ftp://alpha.gnu.org/gnu/sed/sed-4.2.2-pre.tar.bz2;
|
||
sha256 = "11nq06d131y4wmf3drm0yk502d2xc6n5qy82cg88rb9nqd2lj41k";
|
||
};
|
||
patches = [];
|
||
});</programlisting>
|
||
</para>
|
||
|
||
<para>
|
||
In the above example, the name, src and patches of the derivation
|
||
will be overridden, while all other attributes will be retained from the
|
||
original derivation.
|
||
</para>
|
||
|
||
<para>
|
||
The argument <varname>oldAttrs</varname> is used to refer to the attribute set of
|
||
the original derivation.
|
||
</para>
|
||
|
||
</section>
|
||
|
||
<section xml:id="sec-lib-makeOverridable">
|
||
<title>lib.makeOverridable</title>
|
||
|
||
<para>
|
||
The function <varname>lib.makeOverridable</varname> is used to make the result
|
||
of a function easily customizable. This utility only makes sense for functions
|
||
that accept an argument set and return an attribute set.
|
||
</para>
|
||
|
||
<para>
|
||
Example usage:
|
||
|
||
<programlisting>f = { a, b }: { result = a+b; }
|
||
c = lib.makeOverridable f { a = 1; b = 2; }</programlisting>
|
||
|
||
</para>
|
||
|
||
<para>
|
||
The variable <varname>c</varname> is the value of the <varname>f</varname> function
|
||
applied with some default arguments. Hence the value of <varname>c.result</varname>
|
||
is <literal>3</literal>, in this example.
|
||
</para>
|
||
|
||
<para>
|
||
The variable <varname>c</varname> however also has some additional functions, like
|
||
<link linkend="sec-pkg-override">c.override</link> which can be used to
|
||
override the default arguments. In this example the value of
|
||
<varname>(c.override { a = 4; }).result</varname> is 6.
|
||
</para>
|
||
|
||
</section>
|
||
|
||
|
||
<section xml:id="sec-fhs-environments">
|
||
<title>buildFHSChrootEnv/buildFHSUserEnv</title>
|
||
|
||
<para>
|
||
<function>buildFHSChrootEnv</function> and
|
||
<function>buildFHSUserEnv</function> provide a way to build and run
|
||
FHS-compatible lightweight sandboxes. They get their own isolated root with
|
||
binded <filename>/nix/store</filename>, so their 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.
|
||
</para>
|
||
|
||
<para>
|
||
<function>buildFHSChrootEnv</function> allows to create persistent
|
||
environments, which can be constructed, deconstructed and entered by
|
||
multiple users at once. A downside is that it requires
|
||
<literal>root</literal> access for both those who create and destroy and
|
||
those who enter it. It can be useful to create environments for daemons that
|
||
one can enter and observe.
|
||
</para>
|
||
|
||
<para>
|
||
<function>buildFHSUserEnv</function> uses Linux namespaces feature to create
|
||
temporary lightweight environments which are destroyed after all child
|
||
processes exit. It does not require root access, and can be useful to create
|
||
sandboxes and wrap applications.
|
||
</para>
|
||
|
||
<para>
|
||
Those functions both rely on <function>buildFHSEnv</function>, which creates
|
||
an actual directory structure given a list of necessary packages and extra
|
||
build commands.
|
||
<function>buildFHSChrootEnv</function> and <function>buildFHSUserEnv</function>
|
||
both accept those arguments which are passed to
|
||
<function>buildFHSEnv</function>:
|
||
</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).</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).</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>extraBuildCommandsMulti</literal>, but
|
||
executed only on multilib architectures.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
<para>
|
||
Additionally, <function>buildFHSUserEnv</function> accepts
|
||
<literal>runScript</literal> parameter, which is a command that would be
|
||
executed inside the sandbox and passed all the command line arguments. It
|
||
default to <literal>bash</literal>.
|
||
</para>
|
||
<para>
|
||
It also uses <literal>CHROOTENV_EXTRA_BINDS</literal> environment variable
|
||
for binding extra directories in the sandbox to outside places. The format of
|
||
the variable is <literal>/mnt=test-mnt:/data</literal>, where
|
||
<literal>/mnt</literal> would be mounted as <literal>/test-mnt</literal>
|
||
and <literal>/data</literal> would be mounted as <literal>/data</literal>.
|
||
<literal>extraBindMounts</literal> array argument to
|
||
<function>buildFHSUserEnv</function> function is prepended to this variable.
|
||
Latter entries take priority if defined several times -- i.e. in case of
|
||
<literal>/data=data1:/data=data2</literal> the actual bind path would be
|
||
<literal>/data2</literal>.
|
||
</para>
|
||
<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>
|
||
|
||
</chapter>
|