<section xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
version="5.0"
xml:id="ch-relnotes-0.10">
<title>Release 0.10 (2006-10-06)</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>
