about summary refs log tree commit diff
path: root/doc/manual/release-notes.xml
diff options
context:
space:
mode:
Diffstat (limited to 'doc/manual/release-notes.xml')
-rw-r--r--doc/manual/release-notes.xml2272
1 files changed, 2272 insertions, 0 deletions
diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml
new file mode 100644
index 000000000000..37bb730f4063
--- /dev/null
+++ b/doc/manual/release-notes.xml
@@ -0,0 +1,2272 @@
+<article xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xml:id="sec-relnotes">
+
+<title>Nix Release Notes</title>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.7"><title>Release 1.7 (TBA)</title>
+
+<para>This release has the following changes:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>New built-in function: <function>builtins.toJSON</function>,
+    which returns a JSON representation of a value.</para>
+  </listitem>
+
+  <listitem><para><command>nix-setuid-helper</command> is
+  gone.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.6.1"><title>Release 1.6.1 (October 28, 2013)</title>
+
+<para>This is primarily a bug fix release.  Changes of interest
+are:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix 1.6 accidentally changed the semantics of antiquoted
+    paths in strings, such as <literal>"${/foo}/bar"</literal>.  This
+    release reverts to the Nix 1.5.3 behaviour.</para>
+  </listitem>
+
+  <listitem>
+    <para>Previously, Nix optimised expressions such as
+    <literal>"${<replaceable>expr</replaceable>}"</literal> to
+    <replaceable>expr</replaceable>.  Thus it neither checked whether
+    <replaceable>expr</replaceable> could be coerced to a string, nor
+    applied such coercions.  This meant that
+    <literal>"${123}"</literal> evaluatued to <literal>123</literal>,
+    and <literal>"${./foo}"</literal> evaluated to
+    <literal>./foo</literal> (even though
+    <literal>"${./foo} "</literal> evaluates to
+    <literal>"/nix/store/<replaceable>hash</replaceable>-foo "</literal>).
+    Nix now checks the type of antiquoted expressions and
+    applies coercions.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now shows the exact position of undefined variables.  In
+    particular, undefined variable errors in a <literal>with</literal>
+    previously didn't show <emphasis>any</emphasis> position
+    information, so this makes it a lot easier to fix such
+    errors.</para>
+  </listitem>
+
+  <listitem>
+    <para>Undefined variables are now treated consistently.
+    Previously, the <function>tryEval</function> function would catch
+    undefined variables inside a <literal>with</literal> but not
+    outside.  Now <function>tryEval</function> never catches undefined
+    variables.</para>
+  </listitem>
+
+  <listitem>
+    <para>Bash completion in <command>nix-shell</command> now works
+    correctly.</para>
+  </listitem>
+
+  <listitem>
+    <para>Stack traces are less verbose: they no longer show calls to
+    builtin functions and only show a single line for each derivation
+    on the call stack.</para>
+  </listitem>
+
+  <listitem>
+    <para>New built-in function: <function>builtins.typeOf</function>,
+    which returns the type of its argument as a string.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.6.0"><title>Release 1.6 (September 10, 2013)</title>
+
+<para>In addition to the usual bug fixes, this release has several new
+features:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The command <command>nix-build --run-env</command> has been
+    renamed to <command>nix-shell</command>.</para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-shell</command> now sources
+    <filename>$stdenv/setup</filename> <emphasis>inside</emphasis> the
+    interactive shell, rather than in a parent shell.  This ensures
+    that shell functions defined by <literal>stdenv</literal> can be
+    used in the interactive shell.</para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-shell</command> has a new flag
+    <option>--pure</option> to clear the environment, so you get an
+    environment that more closely corresponds to the “real” Nix build.
+    </para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-shell</command> now sets the shell prompt
+    (<envar>PS1</envar>) to ensure that Nix shells are distinguishable
+    from your regular shells.</para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-env</command> no longer requires a
+    <literal>*</literal> argument to match all packages, so
+    <literal>nix-env -qa</literal> is equivalent to <literal>nix-env
+    -qa '*'</literal>.</para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-env -i</command> has a new flag
+    <option>--remove-all</option> (<option>-r</option>) to remove all
+    previous packages from the profile.  This makes it easier to do
+    declarative package management similar to NixOS’s
+    <option>environment.systemPackages</option>.  For instance, if you
+    have a specification <filename>my-packages.nix</filename> like this:
+
+<programlisting>
+with import &lt;nixpkgs> {};
+[ thunderbird
+  geeqie
+  ...
+]
+</programlisting>
+
+    then after any change to this file, you can run:
+
+<screen>
+$ nix-env -f my-packages.nix -ir
+</screen>
+
+    to update your profile to match the specification.</para>
+  </listitem>
+
+  <listitem>
+    <para>The ‘<literal>with</literal>’ language construct is now more
+    lazy.  It only evaluates its argument if a variable might actually
+    refer to an attribute in the argument.  For instance, this now
+    works:
+
+<programlisting>
+let
+  pkgs = with pkgs; { foo = "old"; bar = foo; } // overrides;
+  overrides = { foo = "new"; };
+in pkgs.bar
+</programlisting>
+
+    This evaluates to <literal>"new"</literal>, while previously it
+    gave an “infinite recursion” error.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now has proper integer arithmetic operators. For
+    instance, you can write <literal>x + y</literal> instead of
+    <literal>builtins.add x y</literal>, or <literal>x &lt;
+    y</literal> instead of <literal>builtins.lessThan x y</literal>.
+    The comparison operators also work on strings.</para>
+  </listitem>
+
+  <listitem>
+    <para>On 64-bit systems, Nix integers are now 64 bits rather than
+    32 bits.</para>
+  </listitem>
+
+  <listitem>
+    <para>When using the Nix daemon, the <command>nix-daemon</command>
+    worker process now runs on the same CPU as the client, on systems
+    that support setting CPU affinity.  This gives a significant speedup
+    on some systems.</para>
+  </listitem>
+
+  <listitem>
+    <para>If a stack overflow occurs in the Nix evaluator, you now get
+    a proper error message (rather than “Segmentation fault”) on some
+    systems.</para>
+  </listitem>
+
+  <listitem>
+    <para>In addition to directories, you can now bind-mount regular
+    files in chroots through the (now misnamed) option
+    <option>build-chroot-dirs</option>.</para>
+  </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Domen Kožar, Eelco Dolstra,
+Florian Friesdorf, Gergely Risko, Ivan Kozik, Ludovic Courtès and Shea
+Levy.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.5.3"><title>Release 1.5.3 (June 17, 2013)</title>
+
+<para>This is primarily a bug fix release.  The following changes are
+noteworthy:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Yet another security bug involving hard links to files
+    outside the store was fixed.  This bug only affected multi-user
+    installations that do not have hard link restrictions
+    enabled.  (NixOS is thus not vulnerable.)</para>
+  </listitem>
+
+  <listitem>
+    <para>The default binary cache URL has changed from
+    <uri>http://nixos.org/binary-cache</uri> to
+    <uri>http://cache.nixos.org</uri>.  The latter is hosted on Amazon
+    CloudFront (courtesy of <link
+    xlink:href="http://www.logicblox.com/">LogicBlox</link>) and
+    should provide better performance for users in both Europe and
+    North America.</para>
+  </listitem>
+
+  <listitem>
+    <para>The binary cache substituter now prints a warning message if
+    fetching information from the cache takes more than five seconds.
+    Thus network or server problems no longer make Nix appear to just
+    hang.</para>
+  </listitem>
+
+  <listitem>
+    <para>Stack traces now show function names, e.g.
+<screen>
+while evaluating `concatMapStrings' at `<replaceable>...</replaceable>/nixpkgs/pkgs/lib/strings.nix:18:25':
+</screen>
+      Also, if a function is called with an unexpected argument, Nix
+      now shows the name of the argument.
+    </para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.5.2"><title>Release 1.5.2 (May 13, 2013)</title>
+
+<para>This is primarily a bug fix release.  It has contributions from
+Eelco Dolstra, Lluís Batlle i Rossell and Shea Levy.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.5.1"><title>Release 1.5.1 (February 28, 2013)</title>
+
+<para>The bug fix to the bug fix had a bug itself, of course.  But
+this time it will work for sure!</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.5"><title>Release 1.5 (February 27, 2013)</title>
+
+<para>This is a brown paper bag release to fix a regression introduced
+by the hard link security fix in 1.4.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.4"><title>Release 1.4 (February 26, 2013)</title>
+
+<para>This release fixes a security bug in multi-user operation.  It
+was possible for derivations to cause the mode of files outside of the
+Nix store to be changed to 444 (read-only but world-readable) by
+creating hard links to those files (<link
+xlink:href="https://github.com/NixOS/nix/commit/5526a282b5b44e9296e61e07d7d2626a79141ac4">details</link>).</para>
+
+<para>There are also the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem><para>New built-in function:
+  <function>builtins.hashString</function>.</para></listitem>
+
+  <listitem><para>Build logs are now stored in
+  <filename>/nix/var/log/nix/drvs/<replaceable>XX</replaceable>/</filename>,
+  where <replaceable>XX</replaceable> is the first two characters of
+  the derivation.  This is useful on machines that keep a lot of build
+  logs (such as Hydra servers).</para></listitem>
+
+  <listitem><para>The function <function>corepkgs/fetchurl</function>
+  can now make the downloaded file executable.  This will allow
+  getting rid of all bootstrap binaries in the Nixpkgs source
+  tree.</para></listitem>
+
+  <listitem><para>Language change: The expression <literal>"${./path}
+  ..."</literal> now evaluates to a string instead of a
+  path.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.3"><title>Release 1.3 (January 4, 2013)</title>
+
+<para>This is primarily a bug fix release.  When this version is first
+run on Linux, it removes any immutable bits from the Nix store and
+increases the schema version of the Nix store.  (The previous release
+removed support for setting the immutable bit; this release clears any
+remaining immutable bits to make certain operations more
+efficient.)</para>
+
+<para>This release has contributions from Eelco Dolstra and Stuart
+Pernsteiner.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.2"><title>Release 1.2 (December 6, 2012)</title>
+
+<para>This release has the following improvements and changes:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix has a new binary substituter mechanism: the
+    <emphasis>binary cache</emphasis>.  A binary cache contains
+    pre-built binaries of Nix packages.  Whenever Nix wants to build a
+    missing Nix store path, it will check a set of binary caches to
+    see if any of them has a pre-built binary of that path.  The
+    configuration setting <option>binary-caches</option> contains a
+    list of URLs of binary caches.  For instance, doing
+<screen>
+$ nix-env -i thunderbird --option binary-caches http://cache.nixos.org
+</screen>
+    will install Thunderbird and its dependencies, using the available
+    pre-built binaries in <uri>http://cache.nixos.org</uri>.
+    The main advantage over the old “manifest”-based method of getting
+    pre-built binaries is that you don’t have to worry about your
+    manifest being in sync with the Nix expressions you’re installing
+    from; i.e., you don’t need to run <command>nix-pull</command> to
+    update your manifest.  It’s also more scalable because you don’t
+    need to redownload a giant manifest file every time.
+    </para>
+
+    <para>A Nix channel can provide a binary cache URL that will be
+    used automatically if you subscribe to that channel.  If you use
+    the Nixpkgs or NixOS channels
+    (<uri>http://nixos.org/channels</uri>) you automatically get the
+    cache <uri>http://cache.nixos.org</uri>.</para>
+
+    <para>Binary caches are created using <command>nix-push</command>.
+    For details on the operation and format of binary caches, see the
+    <command>nix-push</command> manpage.  More details are provided in
+    <link xlink:href="http://lists.science.uu.nl/pipermail/nix-dev/2012-September/009826.html">this
+    nix-dev posting</link>.</para>
+  </listitem>
+
+  <listitem>
+    <para>Multiple output support should now be usable.  A derivation
+    can declare that it wants to produce multiple store paths by
+    saying something like
+<programlisting>
+outputs = [ "lib" "headers" "doc" ];
+</programlisting>
+    This will cause Nix to pass the intended store path of each output
+    to the builder through the environment variables
+    <literal>lib</literal>, <literal>headers</literal> and
+    <literal>doc</literal>.  Other packages can refer to a specific
+    output by referring to
+    <literal><replaceable>pkg</replaceable>.<replaceable>output</replaceable></literal>,
+    e.g.
+<programlisting>
+buildInputs = [ pkg.lib pkg.headers ];
+</programlisting>
+    If you install a package with multiple outputs using
+    <command>nix-env</command>, each output path will be symlinked
+    into the user environment.</para>
+  </listitem>
+
+  <listitem>
+    <para>Dashes are now valid as part of identifiers and attribute
+    names.</para>
+  </listitem>
+
+  <listitem>
+    <para>The new operation <command>nix-store --repair-path</command>
+    allows corrupted or missing store paths to be repaired by
+    redownloading them.  <command>nix-store --verify --check-contents
+    --repair</command> will scan and repair all paths in the Nix
+    store.  Similarly, <command>nix-env</command>,
+    <command>nix-build</command>, <command>nix-instantiate</command>
+    and <command>nix-store --realise</command> have a
+    <option>--repair</option> flag to detect and fix bad paths by
+    rebuilding or redownloading them.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix no longer sets the immutable bit on files in the Nix
+    store.  Instead, the recommended way to guard the Nix store
+    against accidental modification on Linux is to make it a read-only
+    bind mount, like this:
+
+<screen>
+$ mount --bind /nix/store /nix/store
+$ mount -o remount,ro,bind /nix/store
+</screen>
+
+    Nix will automatically make <filename>/nix/store</filename>
+    writable as needed (using a private mount namespace) to allow
+    modifications.</para>
+  </listitem>
+
+  <listitem>
+    <para>Store optimisation (replacing identical files in the store
+    with hard links) can now be done automatically every time a path
+    is added to the store.  This is enabled by setting the
+    configuration option <literal>auto-optimise-store</literal> to
+    <literal>true</literal> (disabled by default).</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now supports <command>xz</command> compression for NARs
+    in addition to <command>bzip2</command>.  It compresses about 30%
+    better on typical archives and decompresses about twice as
+    fast.</para>
+  </listitem>
+
+  <listitem>
+    <para>Basic Nix expression evaluation profiling: setting the
+    environment variable <envar>NIX_COUNT_CALLS</envar> to
+    <literal>1</literal> will cause Nix to print how many times each
+    primop or function was executed.</para>
+  </listitem>
+
+  <listitem>
+    <para>New primops: <varname>concatLists</varname>,
+    <varname>elem</varname>, <varname>elemAt</varname> and
+    <varname>filter</varname>.</para>
+  </listitem>
+
+  <listitem>
+    <para>The command <command>nix-copy-closure</command> has a new
+    flag <option>--use-substitutes</option> (<option>-s</option>) to
+    download missing paths on the target machine using the substitute
+    mechanism.</para>
+  </listitem>
+
+  <listitem>
+    <para>The command <command>nix-worker</command> has been renamed
+    to <command>nix-daemon</command>.  Support for running the Nix
+    worker in “slave” mode has been removed.</para>
+  </listitem>
+
+  <listitem>
+    <para>The <option>--help</option> flag of every Nix command now
+    invokes <command>man</command>.</para>
+  </listitem>
+
+  <listitem>
+    <para>Chroot builds are now supported on systemd machines.</para>
+  </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Eelco Dolstra, Florian
+Friesdorf, Mats Erik Andersson and Shea Levy.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.1"><title>Release 1.1 (July 18, 2012)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>On Linux, when doing a chroot build, Nix now uses various
+    namespace features provided by the Linux kernel to improve
+    build isolation.  Namely:
+    <itemizedlist>
+      <listitem><para>The private network namespace ensures that
+      builders cannot talk to the outside world (or vice versa): each
+      build only sees a private loopback interface.  This also means
+      that two concurrent builds can listen on the same port (e.g. as
+      part of a test) without conflicting with each
+      other.</para></listitem>
+      <listitem><para>The PID namespace causes each build to start as
+      PID 1.  Processes outside of the chroot are not visible to those
+      on the inside.  On the other hand, processes inside the chroot
+      <emphasis>are</emphasis> visible from the outside (though with
+      different PIDs).</para></listitem>
+      <listitem><para>The IPC namespace prevents the builder from
+      communicating with outside processes using SysV IPC mechanisms
+      (shared memory, message queues, semaphores).  It also ensures
+      that all IPC objects are destroyed when the builder
+      exits.</para></listitem>
+      <listitem><para>The UTS namespace ensures that builders see a
+      hostname of <literal>localhost</literal> rather than the actual
+      hostname.</para></listitem>
+      <listitem><para>The private mount namespace was already used by
+      Nix to ensure that the bind-mounts used to set up the chroot are
+      cleaned up automatically.</para></listitem>
+    </itemizedlist>
+    </para>
+  </listitem>
+
+  <listitem>
+    <para>Build logs are now compressed using
+    <command>bzip2</command>.  The command <command>nix-store
+    -l</command> decompresses them on the fly.  This can be disabled
+    by setting the option <literal>build-compress-log</literal> to
+    <literal>false</literal>.</para>
+  </listitem>
+
+  <listitem>
+    <para>The creation of build logs in
+    <filename>/nix/var/log/nix/drvs</filename> can be disabled by
+    setting the new option <literal>build-keep-log</literal> to
+    <literal>false</literal>.  This is useful, for instance, for Hydra
+    build machines.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now reserves some space in
+    <filename>/nix/var/nix/db/reserved</filename> to ensure that the
+    garbage collector can run successfully if the disk is full.  This
+    is necessary because SQLite transactions fail if the disk is
+    full.</para>
+  </listitem>
+
+  <listitem>
+    <para>Added a basic <function>fetchurl</function> function.  This
+    is not intended to replace the <function>fetchurl</function> in
+    Nixpkgs, but is useful for bootstrapping; e.g., it will allow us
+    to get rid of the bootstrap binaries in the Nixpkgs source tree
+    and download them instead.  You can use it by doing
+    <literal>import &lt;nix/fetchurl.nix> { url =
+    <replaceable>url</replaceable>; sha256 =
+    "<replaceable>hash</replaceable>"; }</literal>. (Shea Levy)</para>
+  </listitem>
+
+  <listitem>
+    <para>Improved RPM spec file. (Michel Alexandre Salim)</para>
+  </listitem>
+
+  <listitem>
+    <para>Support for on-demand socket-based activation in the Nix
+    daemon with <command>systemd</command>.</para>
+  </listitem>
+
+  <listitem>
+    <para>Added a manpage for
+    <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+  </listitem>
+
+  <listitem>
+    <para>When using the Nix daemon, the <option>-s</option> flag in
+    <command>nix-env -qa</command> is now much faster.</para>
+  </listitem>
+    
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.0"><title>Release 1.0 (May 11, 2012)</title>
+
+<para>There have been numerous improvements and bug fixes since the
+previous release.  Here are the most significant:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix can now optionally use the Boehm garbage collector.
+    This significantly reduces the Nix evaluator’s memory footprint,
+    especially when evaluating large NixOS system configurations.  It
+    can be enabled using the <option>--enable-gc</option> configure
+    option.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now uses SQLite for its database.  This is faster and
+    more flexible than the old <emphasis>ad hoc</emphasis> format.
+    SQLite is also used to cache the manifests in
+    <filename>/nix/var/nix/manifests</filename>, resulting in a
+    significant speedup.</para>
+  </listitem>
+    
+  <listitem>
+    <para>Nix now has an search path for expressions.  The search path
+    is set using the environment variable <envar>NIX_PATH</envar> and
+    the <option>-I</option> command line option.  In Nix expressions,
+    paths between angle brackets are used to specify files that must
+    be looked up in the search path.  For instance, the expression
+    <literal>&lt;nixpkgs/default.nix></literal> looks for a file
+    <filename>nixpkgs/default.nix</filename> relative to every element
+    in the search path.</para>
+  </listitem>
+
+  <listitem>
+    <para>The new command <command>nix-build --run-env</command>
+    builds all dependencies of a derivation, then starts a shell in an
+    environment containing all variables from the derivation.  This is
+    useful for reproducing the environment of a derivation for
+    development.</para>
+  </listitem>
+
+  <listitem>
+    <para>The new command <command>nix-store --verify-path</command>
+    verifies that the contents of a store path have not
+    changed.</para>
+  </listitem>
+
+  <listitem>
+    <para>The new command <command>nix-store --print-env</command>
+    prints out the environment of a derivation in a format that can be
+    evaluated by a shell.</para>
+  </listitem>
+
+  <listitem>
+    <para>Attribute names can now be arbitrary strings.  For instance,
+    you can write <literal>{ "foo-1.2" = …; "bla bla" = …; }."bla
+    bla"</literal>.</para>
+  </listitem>
+    
+  <listitem>
+    <para>Attribute selection can now provide a default value using
+    the <literal>or</literal> operator.  For instance, the expression
+    <literal>x.y.z or e</literal> evaluates to the attribute
+    <literal>x.y.z</literal> if it exists, and <literal>e</literal>
+    otherwise.</para>
+  </listitem>
+
+  <listitem>
+    <para>The right-hand side of the <literal>?</literal> operator can
+    now be an attribute path, e.g., <literal>attrs ?
+    a.b.c</literal>.</para>
+  </listitem>
+
+  <listitem>
+    <para>On Linux, Nix will now make files in the Nix store immutable
+    on filesystems that support it.  This prevents accidental
+    modification of files in the store by the root user.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix has preliminary support for derivations with multiple
+    outputs.  This is useful because it allows parts of a package to
+    be deployed and garbage-collected separately.  For instance,
+    development parts of a package such as header files or static
+    libraries would typically not be part of the closure of an
+    application, resulting in reduced disk usage and installation
+    time.</para>
+  </listitem>
+
+  <listitem>
+    <para>The Nix store garbage collector is faster and holds the
+    global lock for a shorter amount of time.</para>
+  </listitem>
+
+  <listitem>
+    <para>The option <option>--timeout</option> (corresponding to the
+    configuration setting <literal>build-timeout</literal>) allows you
+    to set an absolute timeout on builds — if a build runs for more than
+    the given number of seconds, it is terminated.  This is useful for
+    recovering automatically from builds that are stuck in an infinite
+    loop but keep producing output, and for which
+    <literal>--max-silent-time</literal> is ineffective.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix development has moved to GitHub (<link
+    xlink:href="https://github.com/NixOS/nix" />).</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.16"><title>Release 0.16 (August 17, 2010)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The Nix expression evaluator is now much faster in most
+    cases: typically, <link
+    xlink:href="http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html">3
+    to 8 times compared to the old implementation</link>.  It also
+    uses less memory.  It no longer depends on the ATerm
+    library.</para>
+  </listitem>
+
+  <listitem>
+    <para>
+      Support for configurable parallelism inside builders.  Build
+      scripts have always had the ability to perform multiple build
+      actions in parallel (for instance, by running <command>make -j
+      2</command>), but this was not desirable because the number of
+      actions to be performed in parallel was not configurable.  Nix
+      now has an option <option>--cores
+      <replaceable>N</replaceable></option> as well as a configuration
+      setting <varname>build-cores =
+      <replaceable>N</replaceable></varname> that causes the
+      environment variable <envar>NIX_BUILD_CORES</envar> to be set to
+      <replaceable>N</replaceable> when the builder is invoked.  The
+      builder can use this at its discretion to perform a parallel
+      build, e.g., by calling <command>make -j
+      <replaceable>N</replaceable></command>.  In Nixpkgs, this can be
+      enabled on a per-package basis by setting the derivation
+      attribute <varname>enableParallelBuilding</varname> to
+      <literal>true</literal>.
+    </para>
+  </listitem>
+
+  <listitem>
+    <para><command>nix-store -q</command> now supports XML output
+    through the <option>--xml</option> flag.</para>
+  </listitem>
+
+  <listitem>
+    <para>Several bug fixes.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.15"><title>Release 0.15 (March 17, 2010)</title>
+
+<para>This is a bug-fix release.  Among other things, it fixes
+building on Mac OS X (Snow Leopard), and improves the contents of
+<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
+in <literal>chroot</literal> builds.</para>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.14"><title>Release 0.14 (February 4, 2010)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The garbage collector now starts deleting garbage much
+    faster than before.  It no longer determines liveness of all paths
+    in the store, but does so on demand.</para>
+  </listitem>
+
+  <listitem>
+    <para>Added a new operation, <command>nix-store --query
+    --roots</command>, that shows the garbage collector roots that
+    directly or indirectly point to the given store paths.</para>
+  </listitem>
+
+  <listitem>
+    <para>Removed support for converting Berkeley DB-based Nix
+    databases to the new schema.</para>
+  </listitem>
+
+  <listitem>
+    <para>Removed the <option>--use-atime</option> and
+    <option>--max-atime</option> garbage collector options.  They were
+    not very useful in practice.</para>
+  </listitem>
+
+  <listitem>
+    <para>On Windows, Nix now requires Cygwin 1.7.x.</para>
+  </listitem>
+
+  <listitem>
+    <para>A few bug fixes.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.13"><title>Release 0.13 (November 5,
+2009)</title>
+
+<para>This is primarily a bug fix release.  It has some new
+features:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Syntactic sugar for writing nested attribute sets.  Instead of
+
+<programlisting>
+{
+  foo = {
+    bar = 123;
+    xyzzy = true;
+  };
+  a = { b = { c = "d"; }; };
+}
+</programlisting>
+
+    you can write
+
+<programlisting>
+{
+  foo.bar = 123;
+  foo.xyzzy = true;
+  a.b.c = "d";
+}
+</programlisting>
+
+    This is useful, for instance, in NixOS configuration files.</para>
+    
+  </listitem>
+
+  <listitem>
+    <para>Support for Nix channels generated by Hydra, the Nix-based
+    continuous build system.  (Hydra generates NAR archives on the
+    fly, so the size and hash of these archives isn’t known in
+    advance.)</para>
+  </listitem>
+
+  <listitem>
+    <para>Support <literal>i686-linux</literal> builds directly on
+    <literal>x86_64-linux</literal> Nix installations.  This is
+    implemented using the <function>personality()</function> syscall,
+    which causes <command>uname</command> to return
+    <literal>i686</literal> in child processes.</para>
+  </listitem>
+  
+  <listitem>
+    <para>Various improvements to the <literal>chroot</literal>
+    support.  Building in a <literal>chroot</literal> works quite well
+    now.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix no longer blocks if it tries to build a path and another
+    process is already building the same path.  Instead it tries to
+    build another buildable path first.  This improves
+    parallelism.</para>
+  </listitem>
+
+  <listitem>
+    <para>Support for large (> 4 GiB) files in NAR archives.</para>
+  </listitem>
+    
+  <listitem>
+    <para>Various (performance) improvements to the remote build
+    mechanism.</para>
+  </listitem>
+    
+  <listitem>
+    <para>New primops: <varname>builtins.addErrorContext</varname> (to
+    add a string to stack traces — useful for debugging),
+    <varname>builtins.isBool</varname>,
+    <varname>builtins.isString</varname>,
+    <varname>builtins.isInt</varname>,
+    <varname>builtins.intersectAttrs</varname>.</para>
+  </listitem>
+
+  <listitem>
+    <para>OpenSolaris support (Sander van der Burg).</para>
+  </listitem>
+
+  <listitem>
+    <para>Stack traces are no longer displayed unless the
+    <option>--show-trace</option> option is used.</para>
+  </listitem>
+
+  <listitem>
+    <para>The scoping rules for <literal>inherit
+    (<replaceable>e</replaceable>) ...</literal> in recursive
+    attribute sets have changed.  The expression
+    <replaceable>e</replaceable> can now refer to the attributes
+    defined in the containing set.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.12"><title>Release 0.12 (November 20,
+2008)</title>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix no longer uses Berkeley DB to store Nix store metadata.
+    The principal advantages of the new storage scheme are: it works
+    properly over decent implementations of NFS (allowing Nix stores
+    to be shared between multiple machines); no recovery is needed
+    when a Nix process crashes; no write access is needed for
+    read-only operations; no more running out of Berkeley DB locks on
+    certain operations.</para>
+
+    <para>You still need to compile Nix with Berkeley DB support if
+    you want Nix to automatically convert your old Nix store to the
+    new schema.  If you don’t need this, you can build Nix with the
+    <filename>configure</filename> option
+    <option>--disable-old-db-compat</option>.</para>
+
+    <para>After the automatic conversion to the new schema, you can
+    delete the old Berkeley DB files:
+
+    <screen>
+$ cd /nix/var/nix/db
+$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</screen>
+
+    The new metadata is stored in the directories
+    <filename>/nix/var/nix/db/info</filename> and
+    <filename>/nix/var/nix/db/referrer</filename>.  Though the
+    metadata is stored in human-readable plain-text files, they are
+    not intended to be human-editable, as Nix is rather strict about
+    the format.</para>
+
+    <para>The new storage schema may or may not require less disk
+    space than the Berkeley DB environment, mostly depending on the
+    cluster size of your file system.  With 1 KiB clusters (which
+    seems to be the <literal>ext3</literal> default nowadays) it
+    usually takes up much less space.</para>
+  </listitem>
+
+  <listitem><para>There is a new substituter that copies paths
+  directly from other (remote) Nix stores mounted somewhere in the
+  filesystem.  For instance, you can speed up an installation by
+  mounting some remote Nix store that already has the packages in
+  question via NFS or <literal>sshfs</literal>.  The environment
+  variable <envar>NIX_OTHER_STORES</envar> specifies the locations of
+  the remote Nix directories,
+  e.g. <literal>/mnt/remote-fs/nix</literal>.</para></listitem>
+
+  <listitem><para>New <command>nix-store</command> operations
+  <option>--dump-db</option> and <option>--load-db</option> to dump
+  and reload the Nix database.</para></listitem>
+
+  <listitem><para>The garbage collector has a number of new options to
+  allow only some of the garbage to be deleted.  The option
+  <option>--max-freed <replaceable>N</replaceable></option> tells the
+  collector to stop after at least <replaceable>N</replaceable> bytes
+  have been deleted.  The option <option>--max-links
+  <replaceable>N</replaceable></option> tells it to stop after the
+  link count on <filename>/nix/store</filename> has dropped below
+  <replaceable>N</replaceable>.  This is useful for very large Nix
+  stores on filesystems with a 32000 subdirectories limit (like
+  <literal>ext3</literal>).  The option <option>--use-atime</option>
+  causes store paths to be deleted in order of ascending last access
+  time.  This allows non-recently used stuff to be deleted.  The
+  option <option>--max-atime <replaceable>time</replaceable></option>
+  specifies an upper limit to the last accessed time of paths that may
+  be deleted.  For instance,
+
+    <screen>
+    $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</screen>
+
+  deletes everything that hasn’t been accessed in two months.</para></listitem>
+
+  <listitem><para><command>nix-env</command> now uses optimistic
+  profile locking when performing an operation like installing or
+  upgrading, instead of setting an exclusive lock on the profile.
+  This allows multiple <command>nix-env -i / -u / -e</command>
+  operations on the same profile in parallel.  If a
+  <command>nix-env</command> operation sees at the end that the profile
+  was changed in the meantime by another process, it will just
+  restart.  This is generally cheap because the build results are
+  still in the Nix store.</para></listitem>
+
+  <listitem><para>The option <option>--dry-run</option> is now
+  supported by <command>nix-store -r</command> and
+  <command>nix-build</command>.</para></listitem>
+
+  <listitem><para>The information previously shown by
+  <option>--dry-run</option> (i.e., which derivations will be built
+  and which paths will be substituted) is now always shown by
+  <command>nix-env</command>, <command>nix-store -r</command> and
+  <command>nix-build</command>.  The total download size of
+  substitutable paths is now also shown.  For instance, a build will
+  show something like
+
+    <screen>
+the following derivations will be built:
+  /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv
+  /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv
+  ...
+the following paths will be downloaded/copied (30.02 MiB):
+  /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4
+  /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6
+  ...</screen>      
+  
+  </para></listitem>
+
+  <listitem><para>Language features:
+
+    <itemizedlist>
+
+      <listitem><para>@-patterns as in Haskell.  For instance, in a
+      function definition
+
+      <programlisting>f = args @ {x, y, z}: <replaceable>...</replaceable>;</programlisting>
+
+      <varname>args</varname> refers to the argument as a whole, which
+      is further pattern-matched against the attribute set pattern
+      <literal>{x, y, z}</literal>.</para></listitem>
+
+      <listitem><para>“<literal>...</literal>” (ellipsis) patterns.
+      An attribute set pattern can now say <literal>...</literal>  at
+      the end of the attribute name list to specify that the function
+      takes <emphasis>at least</emphasis> the listed attributes, while
+      ignoring additional attributes.  For instance,
+
+      <programlisting>{stdenv, fetchurl, fuse, ...}: <replaceable>...</replaceable></programlisting>
+
+      defines a function that accepts any attribute set that includes
+      at least the three listed attributes.</para></listitem>
+
+      <listitem><para>New primops:
+      <varname>builtins.parseDrvName</varname> (split a package name
+      string like <literal>"nix-0.12pre12876"</literal> into its name
+      and version components, e.g. <literal>"nix"</literal> and
+      <literal>"0.12pre12876"</literal>),
+      <varname>builtins.compareVersions</varname> (compare two version
+      strings using the same algorithm that <command>nix-env</command>
+      uses), <varname>builtins.length</varname> (efficiently compute
+      the length of a list), <varname>builtins.mul</varname> (integer
+      multiplication), <varname>builtins.div</varname> (integer
+      division).
+      <!-- <varname>builtins.genericClosure</varname> -->
+      </para></listitem>
+      
+    </itemizedlist>
+
+  </para></listitem>
+
+  <listitem><para><command>nix-prefetch-url</command> now supports
+  <literal>mirror://</literal> URLs, provided that the environment
+  variable <envar>NIXPKGS_ALL</envar> points at a Nixpkgs
+  tree.</para></listitem>
+
+  <listitem><para>Removed the commands
+  <command>nix-pack-closure</command> and
+  <command>nix-unpack-closure</command>.   You can do almost the same
+  thing but much more efficiently by doing <literal>nix-store --export
+  $(nix-store -qR <replaceable>paths</replaceable>) > closure</literal> and
+  <literal>nix-store --import &lt;
+  closure</literal>.</para></listitem>
+
+  <listitem><para>Lots of bug fixes, including a big performance bug in
+  the handling of <literal>with</literal>-expressions.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.11"><title>Release 0.11 (December 31,
+2007)</title>
+
+<para>Nix 0.11 has many improvements over the previous stable release.
+The most important improvement is secure multi-user support.  It also
+features many usability enhancements and language extensions, many of
+them prompted by NixOS, the purely functional Linux distribution based
+on Nix.  Here is an (incomplete) list:</para>
+
+
+<itemizedlist>
+
+
+  <listitem><para>Secure multi-user support.  A single Nix store can
+  now be shared between multiple (possible untrusted) users.  This is
+  an important feature for NixOS, where it allows non-root users to
+  install software.  The old setuid method for sharing a store between
+  multiple users has been removed.  Details for setting up a
+  multi-user store can be found in the manual.</para></listitem>
+
+
+  <listitem><para>The new command <command>nix-copy-closure</command>
+  gives you an easy and efficient way to exchange software between
+  machines.  It copies the missing parts of the closure of a set of
+  store path to or from a remote machine via
+  <command>ssh</command>.</para></listitem>
+
+
+  <listitem><para>A new kind of string literal: strings between double
+  single-quotes (<literal>''</literal>) have indentation
+  “intelligently” removed.  This allows large strings (such as shell
+  scripts or configuration file fragments in NixOS) to cleanly follow
+  the indentation of the surrounding expression.  It also requires
+  much less escaping, since <literal>''</literal> is less common in
+  most languages than <literal>"</literal>.</para></listitem>
+
+
+  <listitem><para><command>nix-env</command> <option>--set</option>
+  modifies the current generation of a profile so that it contains
+  exactly the specified derivation, and nothing else.  For example,
+  <literal>nix-env -p /nix/var/nix/profiles/browser --set
+  firefox</literal> lets the profile named
+  <filename>browser</filename> contain just Firefox.</para></listitem>
+  
+
+  <listitem><para><command>nix-env</command> now maintains
+  meta-information about installed packages in profiles.  The
+  meta-information is the contents of the <varname>meta</varname>
+  attribute of derivations, such as <varname>description</varname> or
+  <varname>homepage</varname>.  The command <literal>nix-env -q --xml
+  --meta</literal> shows all meta-information.</para></listitem>
+
+  
+  <listitem><para><command>nix-env</command> now uses the
+  <varname>meta.priority</varname> attribute of derivations to resolve
+  filename collisions between packages.  Lower priority values denote
+  a higher priority.  For instance, the GCC wrapper package and the
+  Binutils package in Nixpkgs both have a file
+  <filename>bin/ld</filename>, so previously if you tried to install
+  both you would get a collision.  Now, on the other hand, the GCC
+  wrapper declares a higher priority than Binutils, so the former’s
+  <filename>bin/ld</filename> is symlinked in the user
+  environment.</para></listitem>
+
+
+  <listitem><para><command>nix-env -i / -u</command>: instead of
+  breaking package ties by version, break them by priority and version
+  number.  That is, if there are multiple packages with the same name,
+  then pick the package with the highest priority, and only use the
+  version if there are multiple packages with the same
+  priority.</para>
+
+  <para>This makes it possible to mark specific versions/variant in
+  Nixpkgs more or less desirable than others.  A typical example would
+  be a beta version of some package (e.g.,
+  <literal>gcc-4.2.0rc1</literal>) which should not be installed even
+  though it is the highest version, except when it is explicitly
+  selected (e.g., <literal>nix-env -i
+  gcc-4.2.0rc1</literal>).</para></listitem>
+
+
+  <listitem><para><command>nix-env --set-flag</command> allows meta
+  attributes of installed packages to be modified.  There are several
+  attributes that can be usefully modified, because they affect the
+  behaviour of <command>nix-env</command> or the user environment
+  build script:
+
+    <itemizedlist>
+
+      <listitem><para><varname>meta.priority</varname> can be changed
+      to resolve filename clashes (see above).</para></listitem>
+
+      <listitem><para><varname>meta.keep</varname> can be set to
+      <literal>true</literal> to prevent the package from being
+      upgraded or replaced.  Useful if you want to hang on to an older
+      version of a package.</para></listitem>
+
+      <listitem><para><varname>meta.active</varname> can be set to
+      <literal>false</literal> to “disable” the package.  That is, no
+      symlinks will be generated to the files of the package, but it
+      remains part of the profile (so it won’t be garbage-collected).
+      Set it back to <literal>true</literal> to re-enable the
+      package.</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+
+  
+  <listitem><para><command>nix-env -q</command> now has a flag
+  <option>--prebuilt-only</option> (<option>-b</option>) that causes
+  <command>nix-env</command> to show only those derivations whose
+  output is already in the Nix store or that can be substituted (i.e.,
+  downloaded from somewhere).  In other words, it shows the packages
+  that can be installed “quickly”, i.e., don’t need to be built from
+  source.  The <option>-b</option> flag is also available in
+  <command>nix-env -i</command> and <command>nix-env -u</command> to
+  filter out derivations for which no pre-built binary is
+  available.</para></listitem>
+  
+
+  <listitem><para>The new option <option>--argstr</option> (in
+  <command>nix-env</command>, <command>nix-instantiate</command> and
+  <command>nix-build</command>) is like <option>--arg</option>, except
+  that the value is a string.  For example, <literal>--argstr system
+  i686-linux</literal> is equivalent to <literal>--arg system
+  \"i686-linux\"</literal> (note that <option>--argstr</option>
+  prevents annoying quoting around shell arguments).</para></listitem>
+
+
+  <listitem><para><command>nix-store</command> has a new operation
+  <option>--read-log</option> (<option>-l</option>)
+  <parameter>paths</parameter> that shows the build log of the given
+  paths.</para></listitem>
+
+  
+  <!--
+  <listitem><para>TODO: semantic cleanups of string concatenation
+  etc. (mostly in r6740).</para></listitem>
+  -->
+
+
+  <listitem><para>Nix now uses Berkeley DB 4.5.  The database is
+  upgraded automatically, but you should be careful not to use old
+  versions of Nix that still use Berkeley DB 4.4.</para></listitem>
+
+
+  <!-- foo
+  <listitem><para>TODO: option <option>- -reregister</option> in
+  <command>nix-store - -register-validity</command>.</para></listitem>
+  -->
+
+
+  <listitem><para>The option <option>--max-silent-time</option>
+  (corresponding to the configuration setting
+  <literal>build-max-silent-time</literal>) allows you to set a
+  timeout on builds — if a build produces no output on
+  <literal>stdout</literal> or <literal>stderr</literal> for the given
+  number of seconds, it is terminated.  This is useful for recovering
+  automatically from builds that are stuck in an infinite
+  loop.</para></listitem>
+
+
+  <listitem><para><command>nix-channel</command>: each subscribed
+  channel is its own attribute in the top-level expression generated
+  for the channel.  This allows disambiguation (e.g. <literal>nix-env
+  -i -A nixpkgs_unstable.firefox</literal>).</para></listitem>
+
+
+  <listitem><para>The substitutes table has been removed from the
+  database.  This makes operations such as <command>nix-pull</command>
+  and <command>nix-channel --update</command> much, much
+  faster.</para></listitem>
+
+
+  <listitem><para><command>nix-pull</command> now supports
+  bzip2-compressed manifests.  This speeds up
+  channels.</para></listitem>
+
+
+  <listitem><para><command>nix-prefetch-url</command> now has a
+  limited form of caching.  This is used by
+  <command>nix-channel</command> to prevent unnecessary downloads when
+  the channel hasn’t changed.</para></listitem>
+
+
+  <listitem><para><command>nix-prefetch-url</command> now by default
+  computes the SHA-256 hash of the file instead of the MD5 hash.  In
+  calls to <function>fetchurl</function> you should pass the
+  <literal>sha256</literal> attribute instead of
+  <literal>md5</literal>.  You can pass either a hexadecimal or a
+  base-32 encoding of the hash.</para></listitem>
+
+  
+  <listitem><para>Nix can now perform builds in an automatically
+  generated “chroot”.  This prevents a builder from accessing stuff
+  outside of the Nix store, and thus helps ensure purity.  This is an
+  experimental feature.</para></listitem>
+  
+
+  <listitem><para>The new command <command>nix-store
+  --optimise</command> reduces Nix store disk space usage by finding
+  identical files in the store and hard-linking them to each other.
+  It typically reduces the size of the store by something like
+  25-35%.</para></listitem>
+
+  
+  <listitem><para><filename>~/.nix-defexpr</filename> can now be a
+  directory, in which case the Nix expressions in that directory are
+  combined into an attribute set, with the file names used as the
+  names of the attributes.  The command <command>nix-env
+  --import</command> (which set the
+  <filename>~/.nix-defexpr</filename> symlink) is
+  removed.</para></listitem>
+
+
+  <listitem><para>Derivations can specify the new special attribute
+  <varname>allowedReferences</varname> to enforce that the references
+  in the output of a derivation are a subset of a declared set of
+  paths.  For example, if <varname>allowedReferences</varname> is an
+  empty list, then the output must not have any references.  This is
+  used in NixOS to check that generated files such as initial ramdisks
+  for booting Linux don’t have any dependencies.</para></listitem>
+
+
+  <listitem><para>The new attribute
+  <varname>exportReferencesGraph</varname> allows builders access to
+  the references graph of their inputs.  This is used in NixOS for
+  tasks such as generating ISO-9660 images that contain a Nix store
+  populated with the closure of certain paths.</para></listitem>
+
+
+  <listitem><para>Fixed-output derivations (like
+  <function>fetchurl</function>) can define the attribute
+  <varname>impureEnvVars</varname> to allow external environment
+  variables to be passed to builders.  This is used in Nixpkgs to
+  support proxy configuration, among other things.</para></listitem>
+
+
+  <listitem><para>Several new built-in functions:
+  <function>builtins.attrNames</function>,
+  <function>builtins.filterSource</function>,
+  <function>builtins.isAttrs</function>,
+  <function>builtins.isFunction</function>,
+  <function>builtins.listToAttrs</function>,
+  <function>builtins.stringLength</function>,
+  <function>builtins.sub</function>,
+  <function>builtins.substring</function>,
+  <function>throw</function>,
+  <function>builtins.trace</function>,
+  <function>builtins.readFile</function>.</para></listitem>
+
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.10.1 (October 11, 2006)</title>
+
+<para>This release fixes two somewhat obscure bugs that occur when
+evaluating Nix expressions that are stored inside the Nix store
+(<literal>NIX-67</literal>).  These do not affect most users.</para>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.10 (October 6, 2006)</title>
+
+<note><para>This version of Nix uses Berkeley DB 4.4 instead of 4.3.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.3.  In
+particular, if you use a Nix installed through Nix, you should run
+
+<screen>
+$ nix-store --clear-substitutes</screen>
+
+first.</para></note>
+
+<warning><para>Also, the database schema has changed slighted to fix a
+performance issue (see below).  When you run any Nix 0.10 command for
+the first time, the database will be upgraded automatically.  This is
+irreversible.</para></warning>
+
+<itemizedlist>
+
+  
+  <!-- Usability / features -->
+
+  
+  <listitem><para><command>nix-env</command> usability improvements:
+
+    <itemizedlist>
+
+      <listitem><para>An option <option>--compare-versions</option>
+      (or <option>-c</option>) has been added to <command>nix-env
+      --query</command> to allow you to compare installed versions of
+      packages to available versions, or vice versa.  An easy way to
+      see if you are up to date with what’s in your subscribed
+      channels is <literal>nix-env -qc \*</literal>.</para></listitem>
+
+      <listitem><para><literal>nix-env --query</literal> now takes as
+      arguments a list of package names about which to show
+      information, just like <option>--install</option>, etc.: for
+      example, <literal>nix-env -q gcc</literal>.  Note that to show
+      all derivations, you need to specify
+      <literal>\*</literal>.</para></listitem>
+
+      <listitem><para><literal>nix-env -i
+      <replaceable>pkgname</replaceable></literal> will now install
+      the highest available version of
+      <replaceable>pkgname</replaceable>, rather than installing all
+      available versions (which would probably give collisions)
+      (<literal>NIX-31</literal>).</para></listitem>
+
+      <listitem><para><literal>nix-env (-i|-u) --dry-run</literal> now
+      shows exactly which missing paths will be built or
+      substituted.</para></listitem>
+
+      <listitem><para><literal>nix-env -qa --description</literal>
+      shows human-readable descriptions of packages, provided that
+      they have a <literal>meta.description</literal> attribute (which
+      most packages in Nixpkgs don’t have yet).</para></listitem>
+
+    </itemizedlist>
+  
+  </para></listitem>
+  
+
+  <listitem><para>New language features:
+
+    <itemizedlist>
+
+      <listitem><para>Reference scanning (which happens after each
+      build) is much faster and takes a constant amount of
+      memory.</para></listitem>
+
+      <listitem><para>String interpolation.  Expressions like
+
+<programlisting>
+"--with-freetype2-library=" + freetype + "/lib"</programlisting>
+
+      can now be written as
+
+<programlisting>
+"--with-freetype2-library=${freetype}/lib"</programlisting>
+
+      You can write arbitrary expressions within
+      <literal>${<replaceable>...</replaceable>}</literal>, not just
+      identifiers.</para></listitem>
+      
+      <listitem><para>Multi-line string literals.</para></listitem>
+
+      <listitem><para>String concatenations can now involve
+      derivations, as in the example <code>"--with-freetype2-library="
+      + freetype + "/lib"</code>.  This was not previously possible
+      because we need to register that a derivation that uses such a
+      string is dependent on <literal>freetype</literal>.  The
+      evaluator now properly propagates this information.
+      Consequently, the subpath operator (<literal>~</literal>) has
+      been deprecated.</para></listitem>
+
+      <listitem><para>Default values of function arguments can now
+      refer to other function arguments; that is, all arguments are in
+      scope in the default values
+      (<literal>NIX-45</literal>).</para></listitem>
+
+      <!--
+      <listitem><para>TODO: domain checks (r5895).</para></listitem>
+      -->
+
+      <listitem><para>Lots of new built-in primitives, such as
+      functions for list manipulation and integer arithmetic.  See the
+      manual for a complete list.  All primops are now available in
+      the set <varname>builtins</varname>, allowing one to test for
+      the availability of primop in a backwards-compatible
+      way.</para></listitem>
+
+      <listitem><para>Real let-expressions: <literal>let x = ...;
+      ... z = ...; in ...</literal>.</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+
+
+  <listitem><para>New commands <command>nix-pack-closure</command> and
+  <command>nix-unpack-closure</command> than can be used to easily
+  transfer a store path with all its dependencies to another machine.
+  Very convenient whenever you have some package on your machine and
+  you want to copy it somewhere else.</para></listitem>
+
+  
+  <listitem><para>XML support:
+
+    <itemizedlist>
+
+      <listitem><para><literal>nix-env -q --xml</literal> prints the
+      installed or available packages in an XML representation for
+      easy processing by other tools.</para></listitem>
+
+      <listitem><para><literal>nix-instantiate --eval-only
+      --xml</literal> prints an XML representation of the resulting
+      term.  (The new flag <option>--strict</option> forces ‘deep’
+      evaluation of the result, i.e., list elements and attributes are
+      evaluated recursively.)</para></listitem>
+
+      <listitem><para>In Nix expressions, the primop
+      <function>builtins.toXML</function> converts a term to an XML
+      representation.  This is primarily useful for passing structured
+      information to builders.</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+  
+
+  <listitem><para>You can now unambiguously specify which derivation to
+  build or install in <command>nix-env</command>,
+  <command>nix-instantiate</command> and <command>nix-build</command>
+  using the <option>--attr</option> / <option>-A</option> flags, which
+  takes an attribute name as argument.  (Unlike symbolic package names
+  such as <literal>subversion-1.4.0</literal>, attribute names in an
+  attribute set are unique.)  For instance, a quick way to perform a
+  test build of a package in Nixpkgs is <literal>nix-build
+  pkgs/top-level/all-packages.nix -A
+  <replaceable>foo</replaceable></literal>.  <literal>nix-env -q
+  --attr</literal> shows the attribute names corresponding to each
+  derivation.</para></listitem>
+  
+
+  <listitem><para>If the top-level Nix expression used by
+  <command>nix-env</command>, <command>nix-instantiate</command> or
+  <command>nix-build</command> evaluates to a function whose arguments
+  all have default values, the function will be called automatically.
+  Also, the new command-line switch <option>--arg
+  <replaceable>name</replaceable>
+  <replaceable>value</replaceable></option> can be used to specify
+  function arguments on the command line.</para></listitem>
+
+  
+  <listitem><para><literal>nix-install-package --url
+  <replaceable>URL</replaceable></literal> allows a package to be
+  installed directly from the given URL.</para></listitem>
+
+
+  <listitem><para>Nix now works behind an HTTP proxy server; just set
+  the standard environment variables <envar>http_proxy</envar>,
+  <envar>https_proxy</envar>, <envar>ftp_proxy</envar> or
+  <envar>all_proxy</envar> appropriately.  Functions such as
+  <function>fetchurl</function> in Nixpkgs also respect these
+  variables.</para></listitem>
+
+
+  <listitem><para><literal>nix-build -o
+  <replaceable>symlink</replaceable></literal> allows the symlink to
+  the build result to be named something other than
+  <literal>result</literal>.</para></listitem>
+
+
+  <!-- Stability / performance / etc. -->
+
+
+  <listitem><para>Platform support:
+
+    <itemizedlist>
+
+      <listitem><para>Support for 64-bit platforms, provided a <link
+      xlink:href="http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606">suitably
+      patched ATerm library</link> is used.  Also, files larger than 2
+      GiB are now supported.</para></listitem>
+
+      <listitem><para>Added support for Cygwin (Windows,
+      <literal>i686-cygwin</literal>), Mac OS X on Intel
+      (<literal>i686-darwin</literal>) and Linux on PowerPC
+      (<literal>powerpc-linux</literal>).</para></listitem>
+
+      <listitem><para>Users of SMP and multicore machines will
+      appreciate that the number of builds to be performed in parallel
+      can now be specified in the configuration file in the
+      <literal>build-max-jobs</literal> setting.</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+
+  
+  <listitem><para>Garbage collector improvements:
+
+    <itemizedlist>
+
+      <listitem><para>Open files (such as running programs) are now
+      used as roots of the garbage collector.  This prevents programs
+      that have been uninstalled from being garbage collected while
+      they are still running.  The script that detects these
+      additional runtime roots
+      (<filename>find-runtime-roots.pl</filename>) is inherently
+      system-specific, but it should work on Linux and on all
+      platforms that have the <command>lsof</command>
+      utility.</para></listitem>
+
+      <listitem><para><literal>nix-store --gc</literal>
+      (a.k.a. <command>nix-collect-garbage</command>) prints out the
+      number of bytes freed on standard output.  <literal>nix-store
+      --gc --print-dead</literal> shows how many bytes would be freed
+      by an actual garbage collection.</para></listitem>
+
+      <listitem><para><literal>nix-collect-garbage -d</literal>
+      removes all old generations of <emphasis>all</emphasis> profiles
+      before calling the actual garbage collector (<literal>nix-store
+      --gc</literal>).  This is an easy way to get rid of all old
+      packages in the Nix store.</para></listitem>
+
+      <listitem><para><command>nix-store</command> now has an
+      operation <option>--delete</option> to delete specific paths
+      from the Nix store.  It won’t delete reachable (non-garbage)
+      paths unless <option>--ignore-liveness</option> is
+      specified.</para></listitem>
+      
+    </itemizedlist>
+
+  </para></listitem>
+
+  
+  <listitem><para>Berkeley DB 4.4’s process registry feature is used
+  to recover from crashed Nix processes.</para></listitem>
+
+  <!--  <listitem><para>TODO: shared stores.</para></listitem> -->
+
+  <listitem><para>A performance issue has been fixed with the
+  <literal>referer</literal> table, which stores the inverse of the
+  <literal>references</literal> table (i.e., it tells you what store
+  paths refer to a given path).  Maintaining this table could take a
+  quadratic amount of time, as well as a quadratic amount of Berkeley
+  DB log file space (in particular when running the garbage collector)
+  (<literal>NIX-23</literal>).</para></listitem>
+
+  <listitem><para>Nix now catches the <literal>TERM</literal> and
+  <literal>HUP</literal> signals in addition to the
+  <literal>INT</literal> signal.  So you can now do a <literal>killall
+  nix-store</literal> without triggering a database
+  recovery.</para></listitem>
+
+  <listitem><para><command>bsdiff</command> updated to version
+  4.3.</para></listitem>
+
+  <listitem><para>Substantial performance improvements in expression
+  evaluation and <literal>nix-env -qa</literal>, all thanks to <link
+  xlink:href="http://valgrind.org/">Valgrind</link>.  Memory use has
+  been reduced by a factor 8 or so.  Big speedup by memoisation of
+  path hashing.</para></listitem>
+
+  <listitem><para>Lots of bug fixes, notably:
+
+    <itemizedlist>
+
+      <listitem><para>Make sure that the garbage collector can run
+      successfully when the disk is full
+      (<literal>NIX-18</literal>).</para></listitem>
+
+      <listitem><para><command>nix-env</command> now locks the profile
+      to prevent races between concurrent <command>nix-env</command>
+      operations on the same profile
+      (<literal>NIX-7</literal>).</para></listitem>
+
+      <listitem><para>Removed misleading messages from
+      <literal>nix-env -i</literal> (e.g., <literal>installing
+      `foo'</literal> followed by <literal>uninstalling
+      `foo'</literal>) (<literal>NIX-17</literal>).</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+
+  <listitem><para>Nix source distributions are a lot smaller now since
+  we no longer include a full copy of the Berkeley DB source
+  distribution (but only the bits we need).</para></listitem>
+
+  <listitem><para>Header files are now installed so that external
+  programs can use the Nix libraries.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.9.2 (September 21, 2005)</title>
+
+<para>This bug fix release fixes two problems on Mac OS X:
+
+<itemizedlist>
+
+  <listitem><para>If Nix was linked against statically linked versions
+  of the ATerm or Berkeley DB library, there would be dynamic link
+  errors at runtime.</para></listitem>
+
+  <listitem><para><command>nix-pull</command> and
+  <command>nix-push</command> intermittently failed due to race
+  conditions involving pipes and child processes with error messages
+  such as <literal>open2: open(GLOB(0x180b2e4), >&amp;=9) failed: Bad
+  file descriptor at /nix/bin/nix-pull line 77</literal> (issue
+  <literal>NIX-14</literal>).</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.9.1 (September 20, 2005)</title>
+
+<para>This bug fix release addresses a problem with the ATerm library
+when the <option>--with-aterm</option> flag in
+<command>configure</command> was <emphasis>not</emphasis> used.</para>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.9 (September 16, 2005)</title>
+
+<para>NOTE: this version of Nix uses Berkeley DB 4.3 instead of 4.2.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.2.  In
+particular, if you use a Nix installed through Nix, you should run
+
+<screen>
+$ nix-store --clear-substitutes</screen>
+
+first.</para>
+
+
+<itemizedlist>
+
+  <listitem><para>Unpacking of patch sequences is much faster now
+  since we no longer do redundant unpacking and repacking of
+  intermediate paths.</para></listitem>
+
+  <listitem><para>Nix now uses Berkeley DB 4.3.</para></listitem>
+
+  <listitem><para>The <function>derivation</function> primitive is
+  lazier.  Attributes of dependent derivations can mutually refer to
+  each other (as long as there are no data dependencies on the
+  <varname>outPath</varname> and <varname>drvPath</varname> attributes
+  computed by <function>derivation</function>).</para>
+
+  <para>For example, the expression <literal>derivation
+  attrs</literal> now evaluates to (essentially)
+
+  <programlisting>
+attrs // {
+  type = "derivation";
+  outPath = derivation! attrs;
+  drvPath = derivation! attrs;
+}</programlisting>
+
+  where <function>derivation!</function> is a primop that does the
+  actual derivation instantiation (i.e., it does what
+  <function>derivation</function> used to do).  The advantage is that
+  it allows commands such as <command>nix-env -qa</command> and
+  <command>nix-env -i</command> to be much faster since they no longer
+  need to instantiate all derivations, just the
+  <varname>name</varname> attribute.</para>
+
+  <para>Also, it allows derivations to cyclically reference each
+  other, for example,
+
+  <programlisting>
+webServer = derivation {
+  ...
+  hostName = "svn.cs.uu.nl";
+  services = [svnService];
+};
+&#x20;
+svnService = derivation {
+  ...
+  hostName = webServer.hostName;
+};</programlisting>
+
+  Previously, this would yield a black hole (infinite recursion).</para>
+  
+  </listitem>
+
+  <listitem><para><command>nix-build</command> now defaults to using
+  <filename>./default.nix</filename> if no Nix expression is
+  specified.</para></listitem>
+
+  <listitem><para><command>nix-instantiate</command>, when applied to
+  a Nix expression that evaluates to a function, will call the
+  function automatically if all its arguments have
+  defaults.</para></listitem>
+
+  <listitem><para>Nix now uses libtool to build dynamic libraries.
+  This reduces the size of executables.</para></listitem>
+
+  <listitem><para>A new list concatenation operator
+  <literal>++</literal>.  For example, <literal>[1 2 3] ++ [4 5
+  6]</literal> evaluates to <literal>[1 2 3 4 5
+  6]</literal>.</para></listitem>
+
+  <listitem><para>Some currently undocumented primops to support
+  low-level build management using Nix (i.e., using Nix as a Make
+  replacement).  See the commit messages for <literal>r3578</literal>
+  and <literal>r3580</literal>.</para></listitem>
+
+  <listitem><para>Various bug fixes and performance
+  improvements.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.8.1 (April 13, 2005)</title>
+
+<para>This is a bug fix release.</para>
+
+<itemizedlist>
+
+  <listitem><para>Patch downloading was broken.</para></listitem>
+
+  <listitem><para>The garbage collector would not delete paths that
+  had references from invalid (but substitutable)
+  paths.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.8 (April 11, 2005)</title>
+
+<para>NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).
+As a result, <command>nix-pull</command> manifests and channels built
+for Nix 0.7 and below will now work anymore.  However, the Nix
+expression language has not changed, so you can still build from
+source.  Also, existing user environments continue to work.  Nix 0.8
+will automatically upgrade the database schema of previous
+installations when it is first run.</para>
+
+<para>If you get the error message
+
+<screen>
+you have an old-style manifest `/nix/var/nix/manifests/[...]'; please
+delete it</screen>
+
+you should delete previously downloaded manifests:
+
+<screen>
+$ rm /nix/var/nix/manifests/*</screen>
+
+If <command>nix-channel</command> gives the error message
+
+<screen>
+manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
+is too old (i.e., for Nix &lt;= 0.7)</screen>
+
+then you should unsubscribe from the offending channel
+(<command>nix-channel --remove
+<replaceable>URL</replaceable></command>; leave out
+<literal>/MANIFEST</literal>), and subscribe to the same URL, with
+<literal>channels</literal> replaced by <literal>channels-v3</literal>
+(e.g., <link
+xlink:href='http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable'
+/>).</para>
+
+<para>Nix 0.8 has the following improvements:
+
+<itemizedlist>
+
+  <listitem><para>The cryptographic hashes used in store paths are now
+  160 bits long, but encoded in base-32 so that they are still only 32
+  characters long (e.g.,
+  <filename>/nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0</filename>).
+  (This is actually a 160 bit truncation of a SHA-256
+  hash.)</para></listitem>
+
+  <listitem><para>Big cleanups and simplifications of the basic store
+  semantics.  The notion of “closure store expressions” is gone (and
+  so is the notion of “successors”); the file system references of a
+  store path are now just stored in the database.</para>
+
+  <para>For instance, given any store path, you can query its closure:
+
+  <screen>
+$ nix-store -qR $(which firefox)
+... lots of paths ...</screen>
+
+  Also, Nix now remembers for each store path the derivation that
+  built it (the “deriver”):
+
+  <screen>
+$ nix-store -qR $(which firefox)
+/nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv</screen>
+
+  So to see the build-time dependencies, you can do
+
+  <screen>
+$ nix-store -qR $(nix-store -qd $(which firefox))</screen>
+
+  or, in a nicer format:
+
+  <screen>
+$ nix-store -q --tree $(nix-store -qd $(which firefox))</screen>
+
+  </para>
+
+  <para>File system references are also stored in reverse.  For
+  instance, you can query all paths that directly or indirectly use a
+  certain Glibc:
+
+  <screen>
+$ nix-store -q --referrers-closure \
+    /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4</screen>
+
+  </para>
+  
+  </listitem>
+
+  <listitem><para>The concept of fixed-output derivations has been
+  formalised.  Previously, functions such as
+  <function>fetchurl</function> in Nixpkgs used a hack (namely,
+  explicitly specifying a store path hash) to prevent changes to, say,
+  the URL of the file from propagating upwards through the dependency
+  graph, causing rebuilds of everything.  This can now be done cleanly
+  by specifying the <varname>outputHash</varname> and
+  <varname>outputHashAlgo</varname> attributes.  Nix itself checks
+  that the content of the output has the specified hash.  (This is
+  important for maintaining certain invariants necessary for future
+  work on secure shared stores.)</para></listitem>
+
+  <listitem><para>One-click installation :-) It is now possible to
+  install any top-level component in Nixpkgs directly, through the web
+  — see, e.g., <link
+  xlink:href='http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/' />.
+  All you have to do is associate
+  <filename>/nix/bin/nix-install-package</filename> with the MIME type
+  <literal>application/nix-package</literal> (or the extension
+  <filename>.nixpkg</filename>), and clicking on a package link will
+  cause it to be installed, with all appropriate dependencies.  If you
+  just want to install some specific application, this is easier than
+  subscribing to a channel.</para></listitem>
+
+  <listitem><para><command>nix-store -r
+  <replaceable>PATHS</replaceable></command> now builds all the
+  derivations PATHS in parallel.  Previously it did them sequentially
+  (though exploiting possible parallelism between subderivations).
+  This is nice for build farms.</para></listitem>
+
+  <listitem><para><command>nix-channel</command> has new operations
+  <option>--list</option> and
+  <option>--remove</option>.</para></listitem>
+
+  <listitem><para>New ways of installing components into user
+  environments:
+
+  <itemizedlist>
+
+    <listitem><para>Copy from another user environment:
+
+    <screen>
+$ nix-env -i --from-profile .../other-profile firefox</screen>
+
+    </para></listitem>
+
+    <listitem><para>Install a store derivation directly (bypassing the
+    Nix expression language entirely):
+
+    <screen>
+$ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv</screen>
+
+    (This is used to implement <command>nix-install-package</command>,
+    which is therefore immune to evolution in the Nix expression
+    language.)</para></listitem>
+
+    <listitem><para>Install an already built store path directly:
+
+    <screen>
+$ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1</screen>
+
+    </para></listitem>
+
+    <listitem><para>Install the result of a Nix expression specified
+    as a command-line argument:
+
+    <screen>
+$ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'</screen>
+
+    The difference with the normal installation mode is that
+    <option>-E</option> does not use the <varname>name</varname>
+    attributes of derivations.  Therefore, this can be used to
+    disambiguate multiple derivations with the same
+    name.</para></listitem>
+
+  </itemizedlist></para></listitem>
+
+  <listitem><para>A hash of the contents of a store path is now stored
+  in the database after a successful build.  This allows you to check
+  whether store paths have been tampered with: <command>nix-store
+  --verify --check-contents</command>.</para></listitem>
+
+  <listitem>
+
+    <para>Implemented a concurrent garbage collector.  It is now
+    always safe to run the garbage collector, even if other Nix
+    operations are happening simultaneously.</para>
+
+    <para>However, there can still be GC races if you use
+    <command>nix-instantiate</command> and <command>nix-store
+    --realise</command> directly to build things.  To prevent races,
+    use the <option>--add-root</option> flag of those commands.</para>
+
+  </listitem>
+
+  <listitem><para>The garbage collector now finally deletes paths in
+  the right order (i.e., topologically sorted under the “references”
+  relation), thus making it safe to interrupt the collector without
+  risking a store that violates the closure
+  invariant.</para></listitem>
+
+  <listitem><para>Likewise, the substitute mechanism now downloads
+  files in the right order, thus preserving the closure invariant at
+  all times.</para></listitem>
+
+  <listitem><para>The result of <command>nix-build</command> is now
+  registered as a root of the garbage collector.  If the
+  <filename>./result</filename> link is deleted, the GC root
+  disappears automatically.</para></listitem>
+
+  <listitem>
+
+    <para>The behaviour of the garbage collector can be changed
+    globally by setting options in
+    <filename>/nix/etc/nix/nix.conf</filename>.
+
+    <itemizedlist>
+
+      <listitem><para><literal>gc-keep-derivations</literal> specifies
+      whether deriver links should be followed when searching for live
+      paths.</para></listitem>
+
+      <listitem><para><literal>gc-keep-outputs</literal> specifies
+      whether outputs of derivations should be followed when searching
+      for live paths.</para></listitem>
+
+      <listitem><para><literal>env-keep-derivations</literal>
+      specifies whether user environments should store the paths of
+      derivations when they are added (thus keeping the derivations
+      alive).</para></listitem>
+
+    </itemizedlist>
+
+  </para></listitem>
+
+  <listitem><para>New <command>nix-env</command> query flags
+  <option>--drv-path</option> and
+  <option>--out-path</option>.</para></listitem>
+
+  <listitem><para><command>fetchurl</command> allows SHA-1 and SHA-256
+  in addition to MD5.  Just specify the attribute
+  <varname>sha1</varname> or <varname>sha256</varname> instead of
+  <varname>md5</varname>.</para></listitem>
+
+  <listitem><para>Manual updates.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.7 (January 12, 2005)</title>
+
+<itemizedlist>
+
+  <listitem><para>Binary patching.  When upgrading components using
+  pre-built binaries (through nix-pull / nix-channel), Nix can
+  automatically download and apply binary patches to already installed
+  components instead of full downloads.  Patching is “smart”: if there
+  is a <emphasis>sequence</emphasis> of patches to an installed
+  component, Nix will use it.  Patches are currently generated
+  automatically between Nixpkgs (pre-)releases.</para></listitem>
+
+  <listitem><para>Simplifications to the substitute
+  mechanism.</para></listitem>
+
+  <listitem><para>Nix-pull now stores downloaded manifests in
+  <filename>/nix/var/nix/manifests</filename>.</para></listitem>
+
+  <listitem><para>Metadata on files in the Nix store is canonicalised
+  after builds: the last-modified timestamp is set to 0 (00:00:00
+  1/1/1970), the mode is set to 0444 or 0555 (readable and possibly
+  executable by all; setuid/setgid bits are dropped), and the group is
+  set to the default.  This ensures that the result of a build and an
+  installation through a substitute is the same; and that timestamp
+  dependencies are revealed.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.6 (November 14, 2004)</title>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Rewrite of the normalisation engine.
+
+    <itemizedlist>
+
+      <listitem><para>Multiple builds can now be performed in parallel
+      (option <option>-j</option>).</para></listitem>
+
+      <listitem><para>Distributed builds.  Nix can now call a shell
+      script to forward builds to Nix installations on remote
+      machines, which may or may not be of the same platform
+      type.</para></listitem>
+
+      <listitem><para>Option <option>--fallback</option> allows
+      recovery from broken substitutes.</para></listitem>
+
+      <listitem><para>Option <option>--keep-going</option> causes
+      building of other (unaffected) derivations to continue if one
+      failed.</para></listitem>
+
+    </itemizedlist>
+
+    </para>
+
+  </listitem>
+
+  <listitem><para>Improvements to the garbage collector (i.e., it
+  should actually work now).</para></listitem>
+
+  <listitem><para>Setuid Nix installations allow a Nix store to be
+  shared among multiple users.</para></listitem>
+
+  <listitem><para>Substitute registration is much faster
+  now.</para></listitem>
+
+  <listitem><para>A utility <command>nix-build</command> to build a
+  Nix expression and create a symlink to the result int the current
+  directory; useful for testing Nix derivations.</para></listitem>
+
+  <listitem><para>Manual updates.</para></listitem>
+
+  <listitem>
+
+    <para><command>nix-env</command> changes:
+
+    <itemizedlist>
+
+      <listitem><para>Derivations for other platforms are filtered out
+      (which can be overridden using
+      <option>--system-filter</option>).</para></listitem>
+
+      <listitem><para><option>--install</option> by default now
+      uninstall previous derivations with the same
+      name.</para></listitem>
+
+      <listitem><para><option>--upgrade</option> allows upgrading to a
+      specific version.</para></listitem>
+
+      <listitem><para>New operation
+      <option>--delete-generations</option> to remove profile
+      generations (necessary for effective garbage
+      collection).</para></listitem>
+
+      <listitem><para>Nicer output (sorted,
+      columnised).</para></listitem>
+
+    </itemizedlist>
+    
+    </para>
+
+  </listitem>
+
+  <listitem><para>More sensible verbosity levels all around (builder
+  output is now shown always, unless <option>-Q</option> is
+  given).</para></listitem>
+
+  <listitem>
+
+    <para>Nix expression language changes:
+
+    <itemizedlist>
+      
+      <listitem><para>New language construct: <literal>with
+      <replaceable>E1</replaceable>;
+      <replaceable>E2</replaceable></literal> brings all attributes
+      defined in the attribute set <replaceable>E1</replaceable> in
+      scope in <replaceable>E2</replaceable>.</para></listitem>
+
+      <listitem><para>Added a <function>map</function>
+      function.</para></listitem>
+
+      <listitem><para>Various new operators (e.g., string
+      concatenation).</para></listitem>
+
+    </itemizedlist>
+
+    </para>
+
+  </listitem>
+
+  <listitem><para>Expression evaluation is much
+  faster.</para></listitem>
+
+  <listitem><para>An Emacs mode for editing Nix expressions (with
+  syntax highlighting and indentation) has been
+  added.</para></listitem>
+
+  <listitem><para>Many bug fixes.</para></listitem>
+
+</itemizedlist>
+
+</section>
+
+
+
+<!--==================================================================-->
+
+<section><title>Release 0.5 and earlier</title>
+
+<para>Please refer to the Subversion commit log messages.</para>
+
+</section>
+
+
+
+</article>