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<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xml:id="chap-package-notes">
<title>Package Notes</title>
<para>This chapter contains information about how to use and maintain
the Nix expressions for a number of specific packages, such as the
Linux kernel or X.org.</para>
<!--============================================================-->
<section xml:id="sec-linux-kernel">
<title>Linux kernel</title>
<para>The Nix expressions to build the Linux kernel are in <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/os-specific/linux/kernel"><filename>pkgs/os-specific/linux/kernel</filename></link>.</para>
<para>The function that builds the kernel has an argument
<varname>kernelPatches</varname> which should be a list of
<literal>{name, patch, extraConfig}</literal> attribute sets, where
<varname>name</varname> is the name of the patch (which is included in
the kernels <varname>meta.description</varname> attribute),
<varname>patch</varname> is the patch itself (possibly compressed),
and <varname>extraConfig</varname> (optional) is a string specifying
extra options to be concatenated to the kernel configuration file
(<filename>.config</filename>).</para>
<para>The kernel derivation exports an attribute
<varname>features</varname> specifying whether optional functionality
is or isnt enabled. This is used in NixOS to implement
kernel-specific behaviour. For instance, if the kernel has the
<varname>iwlwifi</varname> feature (i.e. has built-in support for
Intel wireless chipsets), then NixOS doesnt have to build the
external <varname>iwlwifi</varname> package:
<programlisting>
modulesTree = [kernel]
++ pkgs.lib.optional (!kernel.features ? iwlwifi) kernelPackages.iwlwifi
++ ...;
</programlisting>
</para>
<para>How to add a new (major) version of the Linux kernel to Nixpkgs:
<orderedlist>
<listitem>
<para>Copy the old Nix expression
(e.g. <filename>linux-2.6.21.nix</filename>) to the new one
(e.g. <filename>linux-2.6.22.nix</filename>) and update it.</para>
</listitem>
<listitem>
<para>Add the new kernel to <filename>all-packages.nix</filename>
(e.g., create an attribute
<varname>kernel_2_6_22</varname>).</para>
</listitem>
<listitem>
<para>Now were going to update the kernel configuration. First
unpack the kernel. Then for each supported platform
(<literal>i686</literal>, <literal>x86_64</literal>,
<literal>uml</literal>) do the following:
<orderedlist>
<listitem>
<para>Make an copy from the old
config (e.g. <filename>config-2.6.21-i686-smp</filename>) to
the new one
(e.g. <filename>config-2.6.22-i686-smp</filename>).</para>
</listitem>
<listitem>
<para>Copy the config file for this platform
(e.g. <filename>config-2.6.22-i686-smp</filename>) to
<filename>.config</filename> in the kernel source tree.
</para>
</listitem>
<listitem>
<para>Run <literal>make oldconfig
ARCH=<replaceable>{i386,x86_64,um}</replaceable></literal>
and answer all questions. (For the uml configuration, also
add <literal>SHELL=bash</literal>.) Make sure to keep the
configuration consistent between platforms (i.e. dont
enable some feature on <literal>i686</literal> and disable
it on <literal>x86_64</literal>).
</para>
</listitem>
<listitem>
<para>If needed you can also run <literal>make
menuconfig</literal>:
<screen>
$ nix-env -i ncurses
$ export NIX_CFLAGS_LINK=-lncurses
$ make menuconfig ARCH=<replaceable>arch</replaceable></screen>
</para>
</listitem>
<listitem>
<para>Copy <filename>.config</filename> over the new config
file (e.g. <filename>config-2.6.22-i686-smp</filename>).</para>
</listitem>
</orderedlist>
</para>
</listitem>
<listitem>
<para>Test building the kernel: <literal>nix-build -A
kernel_2_6_22</literal>. If it compiles, ship it! For extra
credit, try booting NixOS with it.</para>
</listitem>
<listitem>
<para>It may be that the new kernel requires updating the external
kernel modules and kernel-dependent packages listed in the
<varname>linuxPackagesFor</varname> function in
<filename>all-packages.nix</filename> (such as the NVIDIA drivers,
AUFS, etc.). If the updated packages arent backwards compatible
with older kernels, you may need to keep the older versions
around.</para>
</listitem>
</orderedlist>
</para>
</section>
<!--============================================================-->
<section xml:id="sec-xorg">
<title>X.org</title>
<para>The Nix expressions for the X.org packages reside in
<filename>pkgs/servers/x11/xorg/default.nix</filename>. This file is
automatically generated from lists of tarballs in an X.org release.
As such it should not be modified directly; rather, you should modify
the lists, the generator script or the file
<filename>pkgs/servers/x11/xorg/overrides.nix</filename>, in which you
can override or add to the derivations produced by the
generator.</para>
<para>The generator is invoked as follows:
<screen>
$ cd pkgs/servers/x11/xorg
$ cat tarballs-7.5.list extra.list old.list \
| perl ./generate-expr-from-tarballs.pl
</screen>
For each of the tarballs in the <filename>.list</filename> files, the
script downloads it, unpacks it, and searches its
<filename>configure.ac</filename> and <filename>*.pc.in</filename>
files for dependencies. This information is used to generate
<filename>default.nix</filename>. The generator caches downloaded
tarballs between runs. Pay close attention to the <literal>NOT FOUND:
<replaceable>name</replaceable></literal> messages at the end of the
run, since they may indicate missing dependencies. (Some might be
optional dependencies, however.)</para>
<para>A file like <filename>tarballs-7.5.list</filename> contains all
tarballs in a X.org release. It can be generated like this:
<screen>
$ export i="mirror://xorg/X11R7.4/src/everything/"
$ cat $(PRINT_PATH=1 nix-prefetch-url $i | tail -n 1) \
| perl -e 'while (&lt;>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'i'}$2\n"; }; }' \
| sort > tarballs-7.4.list
</screen>
<filename>extra.list</filename> contains libraries that arent part of
X.org proper, but are closely related to it, such as
<literal>libxcb</literal>. <filename>old.list</filename> contains
some packages that were removed from X.org, but are still needed by
some people or by other packages (such as
<varname>imake</varname>).</para>
<para>If the expression for a package requires derivation attributes
that the generator cannot figure out automatically (say,
<varname>patches</varname> or a <varname>postInstall</varname> hook),
you should modify
<filename>pkgs/servers/x11/xorg/overrides.nix</filename>.</para>
</section>
<!--============================================================-->
<!--
<section>
<title>Gnome</title>
<para>* Expression is auto-generated</para>
<para>* How to update</para>
</section>
-->
<!--============================================================-->
<!--
<section>
<title>GCC</title>
<para>…</para>
</section>
-->
<!--============================================================-->
<section xml:id="sec-eclipse">
<title>Eclipse</title>
<para>
The Nix expressions related to the Eclipse platform and IDE are in
<link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/eclipse"><filename>pkgs/applications/editors/eclipse</filename></link>.
</para>
<para>
Nixpkgs provides a number of packages that will install Eclipse in
its various forms, these range from the bare-bones Eclipse
Platform to the more fully featured Eclipse SDK or Scala-IDE
packages and multiple version are often available. It is possible
to list available Eclipse packages by issuing the command:
<screen>
$ nix-env -f '&lt;nixpkgs&gt;' -qaP -A eclipses --description
</screen>
Once an Eclipse variant is installed it can be run using the
<command>eclipse</command> command, as expected. From within
Eclipse it is then possible to install plugins in the usual manner
by either manually specifying an Eclipse update site or by
installing the Marketplace Client plugin and using it to discover
and install other plugins. This installation method provides an
Eclipse installation that closely resemble a manually installed
Eclipse.
</para>
<para>
If you prefer to install plugins in a more declarative manner then
Nixpkgs also offer a number of Eclipse plugins that can be
installed in an <emphasis>Eclipse environment</emphasis>. This
type of environment is created using the function
<varname>eclipseWithPlugins</varname> found inside the
<varname>nixpkgs.eclipses</varname> attribute set. This function
takes as argument <literal>{ eclipse, plugins ? [], jvmArgs ? []
}</literal> where <varname>eclipse</varname> is a one of the
Eclipse packages described above, <varname>plugins</varname> is a
list of plugin derivations, and <varname>jvmArgs</varname> is a
list of arguments given to the JVM running the Eclipse. For
example, say you wish to install the latest Eclipse Platform with
the popular Eclipse Color Theme plugin and also allow Eclipse to
use more RAM. You could then add
<screen>
packageOverrides = pkgs: {
myEclipse = with pkgs.eclipses; eclipseWithPlugins {
eclipse = eclipse-platform;
jvmArgs = [ "-Xmx2048m" ];
plugins = [ plugins.color-theme ];
};
}
</screen>
to your Nixpkgs configuration
(<filename>~/.config/nixpkgs/config.nix</filename>) and install it by
running <command>nix-env -f '&lt;nixpkgs&gt;' -iA
myEclipse</command> and afterward run Eclipse as usual. It is
possible to find out which plugins are available for installation
using <varname>eclipseWithPlugins</varname> by running
<screen>
$ nix-env -f '&lt;nixpkgs&gt;' -qaP -A eclipses.plugins --description
</screen>
</para>
<para>
If there is a need to install plugins that are not available in
Nixpkgs then it may be possible to define these plugins outside
Nixpkgs using the <varname>buildEclipseUpdateSite</varname> and
<varname>buildEclipsePlugin</varname> functions found in the
<varname>nixpkgs.eclipses.plugins</varname> attribute set. Use the
<varname>buildEclipseUpdateSite</varname> function to install a
plugin distributed as an Eclipse update site. This function takes
<literal>{ name, src }</literal> as argument where
<literal>src</literal> indicates the Eclipse update site archive.
All Eclipse features and plugins within the downloaded update site
will be installed. When an update site archive is not available
then the <varname>buildEclipsePlugin</varname> function can be
used to install a plugin that consists of a pair of feature and
plugin JARs. This function takes an argument <literal>{ name,
srcFeature, srcPlugin }</literal> where
<literal>srcFeature</literal> and <literal>srcPlugin</literal> are
the feature and plugin JARs, respectively.
</para>
<para>
Expanding the previous example with two plugins using the above
functions we have
<screen>
packageOverrides = pkgs: {
myEclipse = with pkgs.eclipses; eclipseWithPlugins {
eclipse = eclipse-platform;
jvmArgs = [ "-Xmx2048m" ];
plugins = [
plugins.color-theme
(plugins.buildEclipsePlugin {
name = "myplugin1-1.0";
srcFeature = fetchurl {
url = "http://…/features/myplugin1.jar";
sha256 = "123…";
};
srcPlugin = fetchurl {
url = "http://…/plugins/myplugin1.jar";
sha256 = "123…";
};
});
(plugins.buildEclipseUpdateSite {
name = "myplugin2-1.0";
src = fetchurl {
stripRoot = false;
url = "http://…/myplugin2.zip";
sha256 = "123…";
};
});
];
};
}
</screen>
</para>
</section>
<section xml:id="sec-elm">
<title>Elm</title>
<para>
The Nix expressions for Elm reside in
<filename>pkgs/development/compilers/elm</filename>. They are generated
automatically by <command>update-elm.rb</command> script. One should
specify versions of Elm packages inside the script, clear the
<filename>packages</filename> directory and run the script from inside it.
<literal>elm-reactor</literal> is special because it also has Elm package
dependencies. The process is not automated very much for now -- you should
get the <literal>elm-reactor</literal> source tree (e.g. with
<command>nix-shell</command>) and run <command>elm2nix.rb</command> inside
it. Place the resulting <filename>package.nix</filename> file into
<filename>packages/elm-reactor-elm.nix</filename>.
</para>
</section>
<section xml:id="sec-autojump">
<title>Autojump</title>
<para>
autojump needs the shell integration to be useful but unlike other systems,
nix doesn't have a standard share directory location. This is why a
<command>autojump-share</command> script is shipped that prints the location
of the shared folder. This can then be used in the .bashrc like this:
<screen>
source "$(autojump-share)/autojump.bash"
</screen>
</para>
</section>
<section xml:id="sec-steam">
<title>Steam</title>
<section xml:id="sec-steam-nix">
<title>Steam in Nix</title>
<para>
Steam is distributed as a <filename>.deb</filename> file, for now only
as an i686 package (the amd64 package only has documentation).
When unpacked, it has a script called <filename>steam</filename> that
in ubuntu (their target distro) would go to <filename>/usr/bin
</filename>. When run for the first time, this script copies some
files to the user's home, which include another script that is the
ultimate responsible for launching the steam binary, which is also
in $HOME.
</para>
<para>
Nix problems and constraints:
<itemizedlist>
<listitem><para>We don't have <filename>/bin/bash</filename> and many
scripts point there. Similarly for <filename>/usr/bin/python</filename>
.</para></listitem>
<listitem><para>We don't have the dynamic loader in <filename>/lib
</filename>.</para></listitem>
<listitem><para>The <filename>steam.sh</filename> script in $HOME can
not be patched, as it is checked and rewritten by steam.</para></listitem>
<listitem><para>The steam binary cannot be patched, it's also checked.</para></listitem>
</itemizedlist>
</para>
<para>
The current approach to deploy Steam in NixOS is composing a FHS-compatible
chroot environment, as documented
<link xlink:href="http://sandervanderburg.blogspot.nl/2013/09/composing-fhs-compatible-chroot.html">here</link>.
This allows us to have binaries in the expected paths without disrupting the system,
and to avoid patching them to work in a non FHS environment.
</para>
</section>
<section xml:id="sec-steam-play">
<title>How to play</title>
<para>
For 64-bit systems it's important to have
<programlisting>hardware.opengl.driSupport32Bit = true;</programlisting>
in your <filename>/etc/nixos/configuration.nix</filename>. You'll also need
<programlisting>hardware.pulseaudio.support32Bit = true;</programlisting>
if you are using PulseAudio - this will enable 32bit ALSA apps integration.
To use the Steam controller, you need to add
<programlisting>services.udev.extraRules = ''
SUBSYSTEM=="usb", ATTRS{idVendor}=="28de", MODE="0666"
KERNEL=="uinput", MODE="0660", GROUP="users", OPTIONS+="static_node=uinput"
'';</programlisting>
to your configuration.
</para>
</section>
<section xml:id="sec-steam-troub">
<title>Troubleshooting</title>
<para>
<variablelist>
<varlistentry>
<term>Steam fails to start. What do I do?</term>
<listitem><para>Try to run
<programlisting>strace steam</programlisting>
to see what is causing steam to fail.</para></listitem>
</varlistentry>
<varlistentry>
<term>Using the FOSS Radeon drivers</term>
<listitem><itemizedlist><listitem><para>
The open source radeon drivers need a newer libc++ than is provided
by the default runtime, which leads to a crash on launch. Use
<programlisting>environment.systemPackages = [(pkgs.steam.override { newStdcpp = true; })];</programlisting>
in your config if you get an error like
<programlisting>
libGL error: unable to load driver: radeonsi_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: radeonsi
libGL error: unable to load driver: swrast_dri.so
libGL error: failed to load driver: swrast</programlisting></para></listitem>
<listitem><para>
Steam ships statically linked with a version of libcrypto that
conflics with the one dynamically loaded by radeonsi_dri.so.
If you get the error
<programlisting>steam.sh: line 713: 7842 Segmentation fault (core dumped)</programlisting>
have a look at <link xlink:href="https://github.com/NixOS/nixpkgs/pull/20269">this pull request</link>.
</para></listitem>
</itemizedlist></listitem></varlistentry>
<varlistentry>
<term>Java</term>
<listitem><orderedlist>
<listitem><para>
There is no java in steam chrootenv by default. If you get a message like
<programlisting>/home/foo/.local/share/Steam/SteamApps/common/towns/towns.sh: line 1: java: command not found</programlisting>
You need to add
<programlisting> steam.override { withJava = true; };</programlisting>
to your configuration.
</para></listitem>
</orderedlist></listitem></varlistentry>
</variablelist>
</para>
</section>
<section xml:id="sec-steam-run">
<title>steam-run</title>
<para>
The FHS-compatible chroot used for steam can also be used to run
other linux games that expect a FHS environment.
To do it, add
<programlisting>pkgs.(steam.override {
nativeOnly = true;
newStdcpp = true;
}).run</programlisting>
to your configuration, rebuild, and run the game with
<programlisting>steam-run ./foo</programlisting>
</para>
</section>
</section>
</chapter>