path: root/doc/manual/release-notes.xml

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<article><title>Nix Release Notes</title>


<section><title>Release 0.9</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 (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.,
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.,
  /nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0).  (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 --referers-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., 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 succesful 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
  <quote>references</quote> 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 *sequence* 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
  /nix/var/nix/manifests.</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 overriden 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>