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261 lines
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11 KiB
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="ssec-relnotes-0.11">
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<title>Release 0.11 (December 31, 2007)</title>
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<para>Nix 0.11 has many improvements over the previous stable release.
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The most important improvement is secure multi-user support. It also
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features many usability enhancements and language extensions, many of
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them prompted by NixOS, the purely functional Linux distribution based
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on Nix. Here is an (incomplete) list:</para>
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<itemizedlist>
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<listitem><para>Secure multi-user support. A single Nix store can
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now be shared between multiple (possible untrusted) users. This is
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an important feature for NixOS, where it allows non-root users to
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install software. The old setuid method for sharing a store between
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multiple users has been removed. Details for setting up a
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multi-user store can be found in the manual.</para></listitem>
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<listitem><para>The new command <command>nix-copy-closure</command>
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gives you an easy and efficient way to exchange software between
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machines. It copies the missing parts of the closure of a set of
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store path to or from a remote machine via
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<command>ssh</command>.</para></listitem>
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<listitem><para>A new kind of string literal: strings between double
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single-quotes (<literal>''</literal>) have indentation
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“intelligently” removed. This allows large strings (such as shell
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scripts or configuration file fragments in NixOS) to cleanly follow
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the indentation of the surrounding expression. It also requires
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much less escaping, since <literal>''</literal> is less common in
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most languages than <literal>"</literal>.</para></listitem>
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<listitem><para><command>nix-env</command> <option>--set</option>
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modifies the current generation of a profile so that it contains
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exactly the specified derivation, and nothing else. For example,
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<literal>nix-env -p /nix/var/nix/profiles/browser --set
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firefox</literal> lets the profile named
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<filename>browser</filename> contain just Firefox.</para></listitem>
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<listitem><para><command>nix-env</command> now maintains
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meta-information about installed packages in profiles. The
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meta-information is the contents of the <varname>meta</varname>
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attribute of derivations, such as <varname>description</varname> or
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<varname>homepage</varname>. The command <literal>nix-env -q --xml
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--meta</literal> shows all meta-information.</para></listitem>
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<listitem><para><command>nix-env</command> now uses the
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<varname>meta.priority</varname> attribute of derivations to resolve
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filename collisions between packages. Lower priority values denote
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a higher priority. For instance, the GCC wrapper package and the
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Binutils package in Nixpkgs both have a file
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<filename>bin/ld</filename>, so previously if you tried to install
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both you would get a collision. Now, on the other hand, the GCC
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wrapper declares a higher priority than Binutils, so the former’s
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<filename>bin/ld</filename> is symlinked in the user
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environment.</para></listitem>
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<listitem><para><command>nix-env -i / -u</command>: instead of
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breaking package ties by version, break them by priority and version
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number. That is, if there are multiple packages with the same name,
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then pick the package with the highest priority, and only use the
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version if there are multiple packages with the same
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priority.</para>
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<para>This makes it possible to mark specific versions/variant in
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Nixpkgs more or less desirable than others. A typical example would
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be a beta version of some package (e.g.,
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<literal>gcc-4.2.0rc1</literal>) which should not be installed even
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though it is the highest version, except when it is explicitly
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selected (e.g., <literal>nix-env -i
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gcc-4.2.0rc1</literal>).</para></listitem>
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<listitem><para><command>nix-env --set-flag</command> allows meta
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attributes of installed packages to be modified. There are several
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attributes that can be usefully modified, because they affect the
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behaviour of <command>nix-env</command> or the user environment
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build script:
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<itemizedlist>
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<listitem><para><varname>meta.priority</varname> can be changed
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to resolve filename clashes (see above).</para></listitem>
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<listitem><para><varname>meta.keep</varname> can be set to
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<literal>true</literal> to prevent the package from being
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upgraded or replaced. Useful if you want to hang on to an older
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version of a package.</para></listitem>
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<listitem><para><varname>meta.active</varname> can be set to
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<literal>false</literal> to “disable” the package. That is, no
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symlinks will be generated to the files of the package, but it
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remains part of the profile (so it won’t be garbage-collected).
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Set it back to <literal>true</literal> to re-enable the
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package.</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para><command>nix-env -q</command> now has a flag
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<option>--prebuilt-only</option> (<option>-b</option>) that causes
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<command>nix-env</command> to show only those derivations whose
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output is already in the Nix store or that can be substituted (i.e.,
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downloaded from somewhere). In other words, it shows the packages
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that can be installed “quickly”, i.e., don’t need to be built from
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source. The <option>-b</option> flag is also available in
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<command>nix-env -i</command> and <command>nix-env -u</command> to
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filter out derivations for which no pre-built binary is
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available.</para></listitem>
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<listitem><para>The new option <option>--argstr</option> (in
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<command>nix-env</command>, <command>nix-instantiate</command> and
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<command>nix-build</command>) is like <option>--arg</option>, except
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that the value is a string. For example, <literal>--argstr system
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i686-linux</literal> is equivalent to <literal>--arg system
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\"i686-linux\"</literal> (note that <option>--argstr</option>
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prevents annoying quoting around shell arguments).</para></listitem>
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<listitem><para><command>nix-store</command> has a new operation
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<option>--read-log</option> (<option>-l</option>)
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<parameter>paths</parameter> that shows the build log of the given
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paths.</para></listitem>
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<!--
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<listitem><para>TODO: semantic cleanups of string concatenation
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etc. (mostly in r6740).</para></listitem>
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-->
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<listitem><para>Nix now uses Berkeley DB 4.5. The database is
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upgraded automatically, but you should be careful not to use old
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versions of Nix that still use Berkeley DB 4.4.</para></listitem>
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<!-- foo
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<listitem><para>TODO: option <option>- -reregister</option> in
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<command>nix-store - -register-validity</command>.</para></listitem>
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-->
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<listitem><para>The option <option>--max-silent-time</option>
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(corresponding to the configuration setting
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<literal>build-max-silent-time</literal>) allows you to set a
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timeout on builds — if a build produces no output on
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<literal>stdout</literal> or <literal>stderr</literal> for the given
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number of seconds, it is terminated. This is useful for recovering
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automatically from builds that are stuck in an infinite
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loop.</para></listitem>
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<listitem><para><command>nix-channel</command>: each subscribed
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channel is its own attribute in the top-level expression generated
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for the channel. This allows disambiguation (e.g. <literal>nix-env
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-i -A nixpkgs_unstable.firefox</literal>).</para></listitem>
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<listitem><para>The substitutes table has been removed from the
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database. This makes operations such as <command>nix-pull</command>
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and <command>nix-channel --update</command> much, much
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faster.</para></listitem>
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<listitem><para><command>nix-pull</command> now supports
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bzip2-compressed manifests. This speeds up
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channels.</para></listitem>
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<listitem><para><command>nix-prefetch-url</command> now has a
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limited form of caching. This is used by
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<command>nix-channel</command> to prevent unnecessary downloads when
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the channel hasn’t changed.</para></listitem>
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<listitem><para><command>nix-prefetch-url</command> now by default
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computes the SHA-256 hash of the file instead of the MD5 hash. In
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calls to <function>fetchurl</function> you should pass the
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<literal>sha256</literal> attribute instead of
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<literal>md5</literal>. You can pass either a hexadecimal or a
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base-32 encoding of the hash.</para></listitem>
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<listitem><para>Nix can now perform builds in an automatically
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generated “chroot”. This prevents a builder from accessing stuff
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outside of the Nix store, and thus helps ensure purity. This is an
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experimental feature.</para></listitem>
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<listitem><para>The new command <command>nix-store
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--optimise</command> reduces Nix store disk space usage by finding
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identical files in the store and hard-linking them to each other.
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It typically reduces the size of the store by something like
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25-35%.</para></listitem>
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<listitem><para><filename>~/.nix-defexpr</filename> can now be a
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directory, in which case the Nix expressions in that directory are
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combined into an attribute set, with the file names used as the
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names of the attributes. The command <command>nix-env
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--import</command> (which set the
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<filename>~/.nix-defexpr</filename> symlink) is
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removed.</para></listitem>
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<listitem><para>Derivations can specify the new special attribute
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<varname>allowedReferences</varname> to enforce that the references
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in the output of a derivation are a subset of a declared set of
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paths. For example, if <varname>allowedReferences</varname> is an
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empty list, then the output must not have any references. This is
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used in NixOS to check that generated files such as initial ramdisks
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for booting Linux don’t have any dependencies.</para></listitem>
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<listitem><para>The new attribute
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<varname>exportReferencesGraph</varname> allows builders access to
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the references graph of their inputs. This is used in NixOS for
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tasks such as generating ISO-9660 images that contain a Nix store
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populated with the closure of certain paths.</para></listitem>
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<listitem><para>Fixed-output derivations (like
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<function>fetchurl</function>) can define the attribute
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<varname>impureEnvVars</varname> to allow external environment
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variables to be passed to builders. This is used in Nixpkgs to
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support proxy configuration, among other things.</para></listitem>
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<listitem><para>Several new built-in functions:
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<function>builtins.attrNames</function>,
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<function>builtins.filterSource</function>,
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<function>builtins.isAttrs</function>,
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<function>builtins.isFunction</function>,
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<function>builtins.listToAttrs</function>,
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<function>builtins.stringLength</function>,
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<function>builtins.sub</function>,
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<function>builtins.substring</function>,
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<function>throw</function>,
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<function>builtins.trace</function>,
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<function>builtins.readFile</function>.</para></listitem>
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</itemizedlist>
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</section> |