<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="ssec-relnotes-2.3">

<title>Release 2.3 (2019-09-04)</title>

<para>This is primarily a bug fix release. However, it makes some
incompatible changes:</para>

<itemizedlist>

  <listitem>
    <para>Nix now uses BSD file locks instead of POSIX file
    locks. Because of this, you should not use Nix 2.3 and previous
    releases at the same time on a Nix store.</para>
  </listitem>

</itemizedlist>

<para>It also has the following changes:</para>

<itemizedlist>

  <listitem>
    <para><function>builtins.fetchGit</function>'s <varname>ref</varname>
    argument now allows specifying an absolute remote ref.
    Nix will automatically prefix <varname>ref</varname> with
    <literal>refs/heads</literal> only if <varname>ref</varname> doesn't
    already begin with <literal>refs/</literal>.
    </para>
  </listitem>

  <listitem>
    <para>The installer now enables sandboxing by default on Linux when the
    system has the necessary kernel support.
    </para>
  </listitem>

  <listitem>
    <para>The <literal>max-jobs</literal> setting now defaults to 1.</para>
  </listitem>

  <listitem>
    <para>New builtin functions:
    <literal>builtins.isPath</literal>,
    <literal>builtins.hashFile</literal>.
    </para>
  </listitem>

  <listitem>
    <para>The <command>nix</command> command has a new
    <option>--print-build-logs</option> (<option>-L</option>) flag to
    print build log output to stderr, rather than showing the last log
    line in the progress bar. To distinguish between concurrent
    builds, log lines are prefixed by the name of the package.
    </para>
  </listitem>

  <listitem>
    <para>Builds are now executed in a pseudo-terminal, and the
    <envar>TERM</envar> environment variable is set to
    <literal>xterm-256color</literal>. This allows many programs
    (e.g. <command>gcc</command>, <command>clang</command>,
    <command>cmake</command>) to print colorized log output.</para>
  </listitem>

  <listitem>
    <para>Add <option>--no-net</option> convenience flag. This flag
    disables substituters; sets the <literal>tarball-ttl</literal>
    setting to infinity (ensuring that any previously downloaded files
    are considered current); and disables retrying downloads and sets
    the connection timeout to the minimum. This flag is enabled
    automatically if there are no configured non-loopback network
    interfaces.</para>
  </listitem>

  <listitem>
    <para>Add a <literal>post-build-hook</literal> setting to run a
    program after a build has succeeded.</para>
  </listitem>

  <listitem>
    <para>Add a <literal>trace-function-calls</literal> setting to log
    the duration of Nix function calls to stderr.</para>
  </listitem>

</itemizedlist>

</section>