nixpkgs/doc/package-specific-user-notes.xml

<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="package-specific-user-notes">
 <title>Package-specific usage notes</title>
 <para>
         These chapters includes some notes
         that apply to specific packages and should
         answer some of the frequently asked questions
         related to Nixpkgs use.

  Some useful information related to package use 
  can be found in <link linkend="chap-package-notes">package-specific development notes</link>.

 </para>
 <section xml:id="opengl">
  <title>OpenGL</title>

  <para>
   Packages that use OpenGL have NixOS desktop as their primary target. The
   current solution for loading the GPU-specific drivers is based on
   <literal>libglvnd</literal> and looks for the driver implementation in
   <literal>LD_LIBRARY_PATH</literal>. If you are using a non-NixOS
   GNU/Linux/X11 desktop with free software video drivers, consider launching
   OpenGL-dependent programs from Nixpkgs with Nixpkgs versions of
   <literal>libglvnd</literal> and <literal>mesa_drivers</literal> in
   <literal>LD_LIBRARY_PATH</literal>. For proprietary video drivers you might
   have luck with also adding the corresponding video driver package.
  </para>
 </section>
 <section xml:id="locales">
  <title>Locales</title>

  <para>
   To allow simultaneous use of packages linked against different versions of
   <literal>glibc</literal> with different locale archive formats Nixpkgs
   patches <literal>glibc</literal> to rely on
   <literal>LOCALE_ARCHIVE</literal> environment variable.
  </para>

  <para>
   On non-NixOS distributions this variable is obviously not set. This can
   cause regressions in language support or even crashes in some
   Nixpkgs-provided programs. The simplest way to mitigate this problem is
   exporting the <literal>LOCALE_ARCHIVE</literal> variable pointing to
   <literal>${glibcLocales}/lib/locale/locale-archive</literal>. The drawback
   (and the reason this is not the default) is the relatively large (a hundred
   MiB) size of the full set of locales. It is possible to build a custom set
   of locales by overriding parameters <literal>allLocales</literal> and
   <literal>locales</literal> of the package.
  </para>
 </section>

 <section xml:id="sec-emacs">
  <title>Emacs</title>

  <section xml:id="sec-emacs-config">
   <title>Configuring Emacs</title>

   <para>
    The Emacs package comes with some extra helpers to make it easier to
    configure. <varname>emacsWithPackages</varname> allows you to manage
    packages from ELPA. This means that you will not have to install that
    packages from within Emacs. For instance, if you wanted to use
    <literal>company</literal>, <literal>counsel</literal>,
    <literal>flycheck</literal>, <literal>ivy</literal>,
    <literal>magit</literal>, <literal>projectile</literal>, and
    <literal>use-package</literal> you could use this as a
    <filename>~/.config/nixpkgs/config.nix</filename> override:
   </para>

<screen>
{
  packageOverrides = pkgs: with pkgs; {
    myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
      company
      counsel
      flycheck
      ivy
      magit
      projectile
      use-package
    ]));
  }
}
</screen>

   <para>
    You can install it like any other packages via <command>nix-env -iA
    myEmacs</command>. However, this will only install those packages. It will
    not <literal>configure</literal> them for us. To do this, we need to
    provide a configuration file. Luckily, it is possible to do this from
    within Nix! By modifying the above example, we can make Emacs load a custom
    config file. The key is to create a package that provide a
    <filename>default.el</filename> file in
    <filename>/share/emacs/site-start/</filename>. Emacs knows to load this
    file automatically when it starts.
   </para>

<screen>
{
  packageOverrides = pkgs: with pkgs; rec {
    myEmacsConfig = writeText "default.el" ''
;; initialize package

(require 'package)
(package-initialize 'noactivate)
(eval-when-compile
  (require 'use-package))

;; load some packages

(use-package company
  :bind ("&lt;C-tab&gt;" . company-complete)
  :diminish company-mode
  :commands (company-mode global-company-mode)
  :defer 1
  :config
  (global-company-mode))

(use-package counsel
  :commands (counsel-descbinds)
  :bind (([remap execute-extended-command] . counsel-M-x)
         ("C-x C-f" . counsel-find-file)
         ("C-c g" . counsel-git)
         ("C-c j" . counsel-git-grep)
         ("C-c k" . counsel-ag)
         ("C-x l" . counsel-locate)
         ("M-y" . counsel-yank-pop)))

(use-package flycheck
  :defer 2
  :config (global-flycheck-mode))

(use-package ivy
  :defer 1
  :bind (("C-c C-r" . ivy-resume)
         ("C-x C-b" . ivy-switch-buffer)
         :map ivy-minibuffer-map
         ("C-j" . ivy-call))
  :diminish ivy-mode
  :commands ivy-mode
  :config
  (ivy-mode 1))

(use-package magit
  :defer
  :if (executable-find "git")
  :bind (("C-x g" . magit-status)
         ("C-x G" . magit-dispatch-popup))
  :init
  (setq magit-completing-read-function 'ivy-completing-read))

(use-package projectile
  :commands projectile-mode
  :bind-keymap ("C-c p" . projectile-command-map)
  :defer 5
  :config
  (projectile-global-mode))
    '';
    myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
      (runCommand "default.el" {} ''
mkdir -p $out/share/emacs/site-lisp
cp ${myEmacsConfig} $out/share/emacs/site-lisp/default.el
'')
      company
      counsel
      flycheck
      ivy
      magit
      projectile
      use-package
    ]));
  };
}
</screen>

   <para>
    This provides a fairly full Emacs start file. It will load in addition to
    the user's presonal config. You can always disable it by passing
    <command>-q</command> to the Emacs command.
   </para>

   <para>
    Sometimes <varname>emacsWithPackages</varname> is not enough, as this
    package set has some priorities imposed on packages (with the lowest
    priority assigned to Melpa Unstable, and the highest for packages manually
    defined in <filename>pkgs/top-level/emacs-packages.nix</filename>). But you
    can't control this priorities when some package is installed as a
    dependency. You can override it on per-package-basis, providing all the
    required dependencies manually - but it's tedious and there is always a
    possibility that an unwanted dependency will sneak in through some other
    package. To completely override such a package you can use
    <varname>overrideScope'</varname>.
   </para>

<screen>
overrides = self: super: rec {
  haskell-mode = self.melpaPackages.haskell-mode;
  ...
};
((emacsPackagesNgGen emacs).overrideScope' overrides).emacsWithPackages (p: with p; [
  # here both these package will use haskell-mode of our own choice
  ghc-mod
  dante
])
</screen>
  </section>
 </section>

 <section xml:id="dlib">
  <title>DLib</title>

  <para>
    <link xlink:href="http://dlib.net/">DLib</link> is a modern, C++-based toolkit which
    provides several machine learning algorithms.
  </para>

  <section xml:id="compiling-without-avx-support">
   <title>Compiling without AVX support</title>

   <para>
     Especially older CPUs don't support
     <link xlink:href="https://en.wikipedia.org/wiki/Advanced_Vector_Extensions">AVX</link>
     (<abbrev>Advanced Vector Extensions</abbrev>) instructions that are used by DLib to
     optimize their algorithms.
   </para>

   <para>
    On the affected hardware errors like <literal>Illegal instruction</literal> will occur.
    In those cases AVX support needs to be disabled:
<programlisting>self: super: {
  dlib = super.dlib.override { avxSupport = false; };
}</programlisting>
   </para>
  </section>
 </section>

 <section xml:id="unfree-software">
  <title>Unfree software</title>

  <para>
   All users of Nixpkgs are free software users, and many users (and
   developers) of Nixpkgs want to limit and tightly control their exposure to
   unfree software. At the same time, many users need (or want)
   to run some specific
   pieces of proprietary software. Nixpkgs includes some expressions for unfree
   software packages. By default unfree software cannot be installed and
   doesn’t show up in searches. To allow installing unfree software in a
   single Nix invocation one can export
   <literal>NIXPKGS_ALLOW_UNFREE=1</literal>. For a persistent solution, users
   can set <literal>allowUnfree</literal> in the Nixpkgs configuration.
  </para>

  <para>
   Fine-grained control is possible by defining
   <literal>allowUnfreePredicate</literal> function in config; it takes the
   <literal>mkDerivation</literal> parameter attrset and returns
   <literal>true</literal> for unfree packages that should be allowed.
  </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 or other Steam supported controllers such as
    the DualShock 4 or Nintendo Switch Pro, you need to add
<programlisting>hardware.steam-hardware.enable = true;</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 or nouveau (nvidia) drivers
      </term>
      <listitem>
       <itemizedlist>
        <listitem>
         <para>
          The <literal>newStdcpp</literal> parameter was removed since NixOS
          17.09 and should not be needed anymore.
         </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>

 <section xml:id="sec-citrix">
  <title>Citrix Receiver</title>

  <para>
   The <link xlink:href="https://www.citrix.com/products/receiver/">Citrix
   Receiver</link> is a remote desktop viewer which provides access to
   <link xlink:href="https://www.citrix.com/products/xenapp-xendesktop/">XenDesktop</link>
   installations.
  </para>

  <section xml:id="sec-citrix-base">
   <title>Basic usage</title>

   <para>
    The tarball archive needs to be downloaded manually as the license
    agreements of the vendor need to be accepted first. This is available at
    the
    <link xlink:href="https://www.citrix.com/downloads/citrix-receiver/">download
    page at citrix.com</link>. Then run <literal>nix-prefetch-url
    file://$PWD/linuxx64-$version.tar.gz</literal>. With the archive available
    in the store the package can be built and installed with Nix.
   </para>

   <para>
    <emphasis>Note: it's recommended to install <literal>Citrix
    Receiver</literal> using <literal>nix-env -i</literal> or globally to
    ensure that the <literal>.desktop</literal> files are installed properly
    into <literal>$XDG_CONFIG_DIRS</literal>. Otherwise it won't be possible to
    open <literal>.ica</literal> files automatically from the browser to start
    a Citrix connection.</emphasis>
   </para>
  </section>

  <section xml:id="sec-citrix-custom-certs">
   <title>Custom certificates</title>

   <para>
    The <literal>Citrix Receiver</literal> in <literal>nixpkgs</literal> trusts
    several certificates
    <link xlink:href="https://curl.haxx.se/docs/caextract.html">from the
    Mozilla database</link> by default. However several companies using Citrix
    might require their own corporate certificate. On distros with imperative
    packaging these certs can be stored easily in
    <link xlink:href="https://developer-docs.citrix.com/projects/receiver-for-linux-command-reference/en/13.7/"><literal>$ICAROOT</literal></link>,
    however this directory is a store path in <literal>nixpkgs</literal>. In
    order to work around this issue the package provides a simple mechanism to
    add custom certificates without rebuilding the entire package using
    <literal>symlinkJoin</literal>:
<programlisting>
<![CDATA[with import <nixpkgs> { config.allowUnfree = true; };
let extraCerts = [ ./custom-cert-1.pem ./custom-cert-2.pem /* ... */ ]; in
citrix_receiver.override {
  inherit extraCerts;
}]]>
</programlisting>
   </para>
  </section>
 </section>
</chapter>