nixpkgs/doc/package-notes.xml
John Ericson b9dce11712 lib: Make overrideScope' which takes arguments in the conventional order
The `overrideScope` bound by `makeScope` (via special `callPackage`)
took an override in the form `super: self { … }`. But this is
dangerously close to the `self: super { … }` form used by *everything*
else, even other definitions of `overrideScope`! Since that
implementation did not even share any code either until I changed it
recently in 3cf43547f4, this inconsistency
is almost certainly an oversight and not intentional.

Unfortunately, just as the inconstency is hard to debug if one just
assumes the conventional order, any sudden fix would break existing
overrides in the same hard-to-debug way. So instead of changing the
definition a new `overrideScope'` with the conventional order is added,
and old `overrideScope` deprecated with a warning saying to use
`overrideScope'` instead. That will hopefully get people to stop using
`overrideScope`, freeing our hand to change or remove it in the future.
2018-09-24 17:50:11 -04:00

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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 xml:id="sec-package-notes-gnome">
<title>Gnome</title>
<para>* Expression is auto-generated</para>
<para>* How to update</para>
</section>
-->
<!--============================================================-->
<!--
<section xml:id="sec-package-notes-gcc">
<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-shell-helpers">
<title>Interactive shell helpers</title>
<para>
Some packages provide the shell integration to be more useful. But unlike
other systems, nix doesn't have a standard share directory location. This is
why a bunch <command>PACKAGE-share</command> scripts are shipped that print
the location of the corresponding shared folder. Current list of such
packages is as following:
<itemizedlist>
<listitem>
<para>
<literal>autojump</literal>: <command>autojump-share</command>
</para>
</listitem>
<listitem>
<para>
<literal>fzf</literal>: <command>fzf-share</command>
</para>
</listitem>
</itemizedlist>
E.g. <literal>autojump</literal> can then 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 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-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="sec-weechat">
<title>Weechat</title>
<para>
Weechat can be configured to include your choice of plugins, reducing its
closure size from the default configuration which includes all available
plugins. To make use of this functionality, install an expression that
overrides its configuration such as
<programlisting>weechat.override {configure = {availablePlugins, ...}: {
plugins = with availablePlugins; [ python perl ];
}
}</programlisting>
</para>
<para>
The plugins currently available are <literal>python</literal>,
<literal>perl</literal>, <literal>ruby</literal>, <literal>guile</literal>,
<literal>tcl</literal> and <literal>lua</literal>.
</para>
<para>
The python plugin allows the addition of extra libraries. For instance, the
<literal>inotify.py</literal> script in weechat-scripts requires D-Bus or
libnotify, and the <literal>fish.py</literal> script requires pycrypto. To
use these scripts, use the <literal>python</literal> plugin's
<literal>withPackages</literal> attribute:
<programlisting>weechat.override { configure = {availablePlugins, ...}: {
plugins = with availablePlugins; [
(python.withPackages (ps: with ps; [ pycrypto python-dbus ]))
];
};
}
</programlisting>
</para>
<para>
In order to also keep all default plugins installed, it is possible to use
the following method:
<programlisting>weechat.override { configure = { availablePlugins, ... }: {
plugins = builtins.attrValues (availablePlugins // {
python = availablePlugins.python.withPackages (ps: with ps; [ pycrypto python-dbus ]);
});
}; }
</programlisting>
</para>
</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 licenses
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>