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<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xml:id="chap-installation">
<title>Installation</title>
<section><title>Supported platforms</title>
<para>Nix is currently supported on the following platforms:
<itemizedlist>
<listitem><para>Linux (particularly on x86, x86_64, and
PowerPC).</para></listitem>
<listitem><para>Mac OS X, both on Intel and
PowerPC.</para></listitem>
<listitem><para>FreeBSD (only tested on Intel).</para></listitem>
<listitem><para>Windows through <link
xlink:href="http://www.cygwin.com/">Cygwin</link>.</para>
<warning><para>On Cygwin, Nix <emphasis>must</emphasis> be installed
on an NTFS partition. It will not work correctly on a FAT
partition.</para></warning>
</listitem>
</itemizedlist>
</para>
<para>Nix is pretty portable, so it should work on most other Unix
platforms as well.</para>
</section>
<section><title>Obtaining Nix</title>
<para>The easiest way to obtain Nix is to download a <link
xlink:href="http://www.cs.uu.nl/groups/ST/Trace/Nix">source
distribution</link>. RPMs for Red Hat, SuSE, and Fedora Core are also
available.</para>
<para>Alternatively, the most recent sources of Nix can be obtained
from its <link
xlink:href="https://svn.cs.uu.nl:12443/repos/trace/nix/trunk">Subversion
repository</link>. For example, the following command will check out
the latest revision into a directory called
<filename>nix</filename>:</para>
<screen>
$ svn checkout https://svn.cs.uu.nl:12443/repos/trace/nix/trunk nix</screen>
<para>Likewise, specific releases can be obtained from the <link
xlink:href="https://svn.cs.uu.nl:12443/repos/trace/nix/tags">tags
directory</link> of the repository. If you don't have Subversion, you
can also download an automatically generated <link
xlink:href="https://svn.cs.uu.nl:12443/dist/trace/">compressed
tar-file</link> of the head revision of the trunk.</para>
</section>
<section><title>Prerequisites</title>
<para><emphasis>The following prerequisites only apply when you build
from source</emphasis>. Binary releases (e.g., RPMs) have no
prerequisites.</para>
<para>A fairly recent version of GCC/G++ is required. Version 2.95
and higher should work.</para>
<para>To build this manual and the man-pages you need the
<command>xmllint</command> and <command>xsltproc</command> programs,
which are part of the <literal>libxml2</literal> and
<literal>libxslt</literal> packages, respectively. You also need the
<link
xlink:href="http://docbook.sourceforge.net/projects/xsl/">DocBook XSL
stylesheets</link> and optionally the <link
xlink:href="http://www.docbook.org/schemas/5x"> DocBook 5.0 RELAX NG
schemas</link>. Note that these are only required if you modify the
manual sources or when you are building from the Subversion
repository.</para>
<para>To build the parser, very <emphasis>recent</emphasis> versions
of Bison and Flex are required. (This is because Nix needs GLR
support in Bison and reentrancy support in Flex.) For Bison, you need
version 2.3 or higher (1.875 does <emphasis>not</emphasis> work),
which can be obtained from
the <link xlink:href="ftp://alpha.gnu.org/pub/gnu/bison">GNU FTP
server</link>. For Flex, you need version 2.5.33, which is available
on <link xlink:href="http://lex.sourceforge.net/">SourceForge</link>.
Slightly older versions may also work, but ancient versions like the
ubiquitous 2.5.4a won't. Note that these are only required if you
modify the parser or when you are building from the Subversion
repository.</para>
<para>Nix uses Sleepycat's Berkeley DB and CWI's ATerm library. These
are included in the Nix source distribution. If you build from the
Subversion repository, you must download them yourself and place them
in the <filename>externals/</filename> directory. See
<filename>externals/Makefile.am</filename> for the precise URLs of
these packages. Alternatively, if you already have them installed,
you can use <command>configure</command>'s <option>--with-bdb</option>
and <option>--with-aterm</option> options to point to their respective
locations. Note that Berkeley DB <emphasis>must</emphasis> be version
4.5; other versions may not have compatible database formats.</para>
</section>
<section><title>Building Nix from source</title>
<para>After unpacking or checking out the Nix sources, issue the
following commands:
</para>
<screen>
$ ./configure <replaceable>options...</replaceable>
$ make
$ make install</screen>
<para>When building from the Subversion repository, these should be
preceded by the command:
</para>
<screen>
$ ./boostrap</screen>
<para>The installation path can be specified by passing the
<option>--prefix=<replaceable>prefix</replaceable></option> to
<command>configure</command>. The default installation directory is
<filename>/nix</filename>. You can change this to any location you
like. You must have write permission to the
<replaceable>prefix</replaceable> path.</para>
<warning><para>It is best <emphasis>not</emphasis> to change the
installation prefix from its default, since doing so makes it
impossible to use pre-built binaries from the standard Nixpkgs
channels.</para></warning>
<para>If you want to rebuilt the documentation, pass the full path to
the DocBook RELAX NG schemas and to the DocBook XSL stylesheets using
the
<option>--with-docbook-rng=<replaceable>path</replaceable></option>
and
<option>--with-docbook-xsl=<replaceable>path</replaceable></option>
options.</para>
</section>
<section><title>Installing from RPMs</title>
<para>RPM packages of Nix can be downloaded from <uri
xlink:href="http://www.cs.uu.nl/groups/ST/Trace/Nix">http://www.cs.uu.nl/groups/ST/Trace/Nix</uri>.
These RPMs should work for most fairly recent releases of SuSE and Red
Hat Linux. They have been known to work work on SuSE Linux 8.1 and
9.0, and Red Hat 9.0. In fact, it should work on any RPM-based Linux
distribution based on <literal>glibc</literal> 2.3 or later.</para>
<para>Once downloaded, the RPMs can be installed or upgraded using
<command>rpm -U</command>. For example,</para>
<screen>
$ rpm -U nix-0.5pre664-1.i386.rpm</screen>
<para>The RPMs install into the directory <filename>/nix</filename>.
Nix can be uninstalled using <command>rpm -e nix</command>. After
this it will be necessary to manually remove the Nix store and other
auxiliary data:</para>
<screen>
$ rm -rf /nix/store
$ rm -rf /nix/var</screen>
</section>
<section><title>Upgrading Nix through Nix</title>
<para>You can install the latest stable version of Nix through Nix
itself by subscribing to the channel <link
xlink:href="http://nix.cs.uu.nl/dist/nix/channels-v3/nix-stable" />,
or the latest unstable version by subscribing to the channel<link
xlink:href="http://nix.cs.uu.nl/dist/nix/channels-v3/nix-unstable" />.
You can also do a <link linkend="sec-one-click">one-click
installation</link> by clicking on the package links at <link
xlink:href="http://nix.cs.uu.nl/dist/nix/" />.</para>
</section>
<section><title>Security</title>
<para>Nix has two basic security models. First, it can be used in
“single-user mode”, which is similar to what most other package
management tools do: there is a single user (typically <systemitem
class="username">root</systemitem>) who performs all package
management operations. All other users can then use the installed
packages, but they cannot perform package management operations
themselves.</para>
<para>Alternatively, you can configure Nix in “multi-user mode”. In
this model, all users can perform package management operations — for
instance, every user can install software without requiring root
privileges. Nix ensures that this is secure. For instance, it’s not
possible for one user to overwrite a package used by another user with
a Trojan horse.</para>
<section><title>Single-user mode</title>
<para>In single-user mode, all Nix operations that access the database
in <filename><replaceable>prefix</replaceable>/var/nix/db</filename>
or modify the Nix store in
<filename><replaceable>prefix</replaceable>/store</filename> must be
performed under the user ID that owns those directories. This is
typically <systemitem class="username">root</systemitem>. (If you
install from RPM packages, that’s in fact the default ownership.)
However, on single-user machines, it is often convenient to
<command>chown</command> those directories to your normal user account
so that you don’t have to <command>su</command> to <systemitem
class="username">root</systemitem> all the time.</para>
</section>
<section><title>Multi-user mode</title>
<para></para>
<!--
warning: the nix-builders group should contain *only* the Nix
builders, and nothing else. If the Nix account is compromised, you
can execute programs under the accounts in the nix-builders group, so
it obviously shouldn’t contain any “real” user accounts. So don’t use
an existing group like <literal>users</literal> — just create a new
one.
-->
<note><para>Multi-user mode has one important limitation: only
<systemitem class="username">root</systemitem> can run <command
linkend="sec-nix-pull">nix-pull</command> to register the availability
of pre-built binaries. However, those registrations
<emphasis>are</emphasis> used by all users to speed up
builds.</para></note>
</section>
</section> <!-- end of permissions section -->
<section><title>Using Nix</title>
<para>To use Nix, some environment variables should be set. In
particular, <envar>PATH</envar> should contain the directories
<filename><replaceable>prefix</replaceable>/bin</filename> and
<filename>~/.nix-profile/bin</filename>. The first directory contains
the Nix tools themselves, while <filename>~/.nix-profile</filename> is
a symbolic link to the current <emphasis>user environment</emphasis>
(an automatically generated package consisting of symlinks to
installed packages). The simplest way to set the required environment
variables is to include the file
<filename><replaceable>prefix</replaceable>/etc/profile.d/nix.sh</filename>
in your <filename>~/.bashrc</filename> (or similar), like this:</para>
<screen>
source <replaceable>prefix</replaceable>/etc/profile.d/nix.sh</screen>
</section>
</chapter>
