[Nix-dev] Nix 0.10 released

[Eelco Dolstra]

Hi,

I'm pleased to announce the availability of a new stable release of the
Nix Deployment System.  Release 0.10 can be found at

    http://nix.cs.uu.nl/dist/nix/nix-0.10/

It's been a while since the last release, but as you can see from the
release notes below, we haven't been idle.  This release brings
substantial improvements in functionality and usability.

*** Release notes ***

The release notes can also be found (in a nicer format than ASCII) at
http://nix.cs.uu.nl/dist/nix/nix-0.10/release-notes/.

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

$ nix-store --clear-substitutes

first.

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.

Changes and improvements in this release:

  * nix-env usability improvements:

      o An option --compare-versions (or -c) has been added to nix-env --query
        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 nix-env -qc \*.

      o nix-env --query now takes as arguments a list of package names about
        which to show information, just like --install, etc.: for example,
        nix-env -q gcc. Note that to show all derivations, you need to specify
        \*.

      o nix-env -i pkgname will now install the highest available version of
        pkgname, rather than installing all available versions (which would
        probably give collisions) (NIX-31).

      o nix-env (-i|-u) --dry-run now shows exactly which missing paths will be
        built or substituted.

      o nix-env -qa --description shows human-readable descriptions of
        packages, provided that they have a meta.description attribute (which
        most packages in Nixpkgs don't have yet).

  * New language features:

      o Reference scanning (which happens after each build) is much faster and
        takes a constant amount of memory.

      o String interpolation. Expressions like

        "--with-freetype2-library=" + freetype + "/lib"

        can now be written as

        "--with-freetype2-library=${freetype}/lib"

        You can write arbitrary expressions within ${...}, not just
        identifiers.

      o Multi-line string literals.

      o String concatenations can now involve derivations, as in the example
        "--with-freetype2-library=" + freetype + "/lib". This was not
        previously possible because we need to register that a derivation that
        uses such a string is dependent on freetype. The evaluator now properly
        propagates this information. Consequently, the subpath operator (~) has
        been deprecated.

      o Default values of function arguments can now refer to other function
        arguments; that is, all arguments are in scope in the default values
        (NIX-45).

      o 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 builtins, allowing one
        to test for the availability of primop in a backwards-compatible way.

      o Real let-expressions: let x = ...; ... z = ...; in ....

  * New commands nix-pack-closure and nix-unpack-closure 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.

  * XML support:

      o nix-env -q --xml prints the installed or available packages in an XML
        representation for easy processing by other tools.

      o nix-instantiate --eval-only --xml prints an XML representation of the
        resulting term. (The new flag --strict forces `deep' evaluation of the
        result, i.e., list elements and attributes are evaluated recursively.)

      o In Nix expressions, the primop builtins.toXML converts a term to an XML
        representation. This is primarily useful for passing structured
        information to builders.

  * You can now unambigously specify which derivation to build or install in
    nix-env, nix-instantiate and nix-build using the --attr / -A flags, which
    takes an attribute name as argument. (Unlike symbolic package names such as
    subversion-1.4.0, attribute names in an attribute set are unique.) For
    instance, a quick way to perform a test build of a package in Nixpkgs is
    nix-build pkgs/top-level/all-packages.nix -A foo. nix-env -q --attr shows
    the attribute names corresponding to each derivation.

  * If the top-level Nix expression used by nix-env, nix-instantiate or
    nix-build evaluates to a function whose arguments all have default values,
    the function will be called automatically. Also, the new command-line
    switch --arg name value can be used to specify function arguments on the
    command line.

  * nix-install-package --url URL allows a package to be installed directly
    from the given URL.

  * Nix now works behind an HTTP proxy server; just set the standard
    environment variables http_proxy, https_proxy, ftp_proxy or all_proxy
    appropriately. Functions such as fetchurl in Nixpkgs also respect these
    variables.

  * nix-build -o symlink allows the symlink to the build result to be named
    something other than result.

  * Platform support:

      o Support for 64-bit platforms, provided a suitably patched ATerm library
        is used. Also, files larger than 2 GiB are now supported.

      o Added support for Cygwin (Windows, i686-cygwin), Mac OS X on Intel
        (i686-darwin) and Linux on PowerPC (powerpc-linux).

      o 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 build-max-jobs setting.

  * Garbage collector improvements:

      o 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 (find-runtime-roots.pl) is
        inherently system-specific, but it should work on Linux and on all
        platforms that have the lsof utility.

      o nix-store --gc (a.k.a. nix-collect-garbage) prints out the number of
        bytes freed on standard output. nix-store --gc --print-dead shows how
        many bytes would be freed by an actual garbage collection.

      o nix-collect-garbage -d removes all old generations of all profiles
        before calling the actual garbage collector (nix-store --gc). This is
        an easy way to get rid of all old packages in the Nix store.

      o nix-store now has an operation --delete to delete specific paths from
        the Nix store. It won't delete reachable (non-garbage) paths unless
        --ignore-liveness is specified.

  * Berkeley DB 4.4's process registry feature is used to recover from crashed
    Nix processes.

  * A performance issue has been fixed with the referer table, which stores the
    inverse of the references 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) (NIX-23).

  * Nix now catches the TERM and HUP signals in addition to the INT signal. So
    you can now do a killall nix-store without triggering a database recovery.

  * bsdiff updated to version 4.3.

  * Substantial performance improvements in expression evaluation and nix-env
    -qa, all thanks to Valgrind. Memory use has been reduced by a factor 8 or
    so. Big speedup by memoisation of path hashing.

  * Lots of bug fixes, notably:

      o Make sure that the garbage collector can run succesfully when the disk
        is full (NIX-18).

      o nix-env now locks the profile to prevent races between concurrent
        nix-env operations on the same profile (NIX-7).

      o Removed misleading messages from nix-env -i (e.g., installing `foo'
        followed by uninstalling `foo') (NIX-17).

  * 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).

  * Header files are now installed so that external programs can use the Nix
    libraries.

-- 
Eelco Dolstra | http://www.cs.uu.nl/~eelco