snix/NEWS

Version 0.8 

NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).  As a
result, `nix-pull' 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.

If you get the error message

  you have an old-style manifest `/nix/var/nix/manifests/[...]';
  please delete it

you should delete previously downloaded manifests:

  $ rm /nix/var/nix/manifests/*

If `nix-channel' gives the error message

  manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
  is too old (i.e., for Nix <= 0.7)

then you should unsubscribe from the offending channel (`nix-channel
--remove URL'; leave out `/MANIFEST'), and subscribe to the same URL,
with `channels' replaced by `channels-v3' (e.g.,
http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable).

Nix 0.8 has the following improvements:

* 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.)

* 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.

  For instance, given any store path, you can query its closure:

    $ nix-store -qR $(which firefox)
    ... lots of paths ...

  Also, Nix now remembers for each store path the derivation that
  built it (the "deriver"):

    $ nix-store -qR $(which firefox)
    /nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv

  So to see the build-time dependencies, you can do
  
    $ nix-store -qR $(nix-store -qd $(which firefox))

  or, in a nicer format:

    $ nix-store -q --tree $(nix-store -qd $(which firefox))

  File system references are also stored in reverse.  For instance,
  you can query all paths that directly or indirectly use a certain
  Glibc:

    $ nix-store -q --referers-closure \
        /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4

* The concept of fixed-output derivations has been formalised.
  Previously, functions such as `fetchurl' 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 `outputHash' and `outputHashAlgo'
  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.)

* 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 `/nix/bin/nix-install-package' with the MIME
  type `application/nix-package' (or the extension `.nixpkg'), 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.

* `nix-store -r PATHS' 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.

* `nix-channel' has new operations `--list' and `--remove'.

* New ways of installing components into user environments:

  - Copy from another user environment:

      $ nix-env -i --from-profile .../other-profile firefox

  - Install a store derivation directly (bypassing the Nix expression
    language entirely):

      $ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv

    (This is used to implement `nix-install-package', which is
    therefore immune to evolution in the Nix expression language.)

  - Install an already built store path directly:

      $ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1

  - Install the result of a Nix expression specified as a command-line
    argument:

      $ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'

    The difference with the normal installation mode is that `-E' does
    not use the `name' attributes of derivations.  Therefore, this can
    be used to disambiguate multiple derivations with the same name.

* 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: `nix-store --verify --check-contents'.
    
* Implemented a concurrent garbage collector.  It is now always safe
  to run the garbage collector, even if other Nix operations are
  happening simultaneously.

  However, there can still be GC races if you use `nix-instantiate'
  and `nix-store -r' directly to build things.  To prevent races, use
  the `--add-root' flag of those commands.

* The garbage collector now finally deletes paths in the right order
  (i.e., topologically sorted under the `references' relation), thus
  making it safe to interrupt the collector without risking a store
  that violates the closure invariant.

* Likewise, the substitute mechanism now downloads files in the right
  order, thus preserving the closure invariant at all times.

* The result of `nix-build' is now registered as a root of the garbage
  collector.  If the `./result' link is deleted, the GC root
  disappears automatically.

* The behaviour of the garbage collector can be changed globally by
  setting options in `/nix/etc/nix/nix.conf'.

  - `gc-keep-derivations' specifies whether deriver links should be
    followed when searching for live paths.

  - `gc-keep-outputs' specifies whether outputs of derivations should
    be followed when searching for live paths.
  
  - `env-keep-derivations' specifies whether user environments should
    store the paths of derivations when they are added (thus keeping
    the derivations alive).

* New `nix-env' query flags `--drv-path' and `--out-path'.

* `fetchurl' allows SHA-1 and SHA-256 in addition to MD5.  Just
  specify the attribute `sha1' or `sha256' instead of `md5'.

  
Version 0.7 (January 12, 2005)

* 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.

* Simplifications to the substitute mechanism.

* Nix-pull now stores downloaded manifests in /nix/var/nix/manifests.

* 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.


Version 0.6 (November 14, 2004)

Major changes include the following:

* Rewrite of the normalisation engine.

  * Multiple builds can now be performed in parallel (option `-j').

  * 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.

  * Option `--fallback' allows recovery from broken substitutes.

  * Option `--keep-going' causes building of other (unaffected)
    derivations to continue if one failed.
    
* Improvements to the garbage collector (i.e., it should actually work
  now).

* Setuid Nix installations allow a Nix store to be shared among
  multiple users.

* Substitute registration is much faster now.

* A utility `nix-build' to build a Nix expression and create a symlink
  to the result int the current directory; useful for testing Nix
  derivations.

* Manual updates.

* `nix-env' changes:

  * Derivations for other platforms are filtered out (which can be
    overriden using `--system-filter').

  * `--install' by default now uninstall previous derivations with the
    same name.

  * `--upgrade' allows upgrading to a specific version.

  * New operation `--delete-generations' to remove profile
    generations (necessary for effective garbage collection).

  * Nicer output (sorted, columnised).

* More sensible verbosity levels all around (builder output is now
  shown always, unless `-Q' is given).

* Nix expression language changes:

  * New language construct: `with E1; E2' brings all attributes
    defined in the attribute set E1 in scope in E2.

  * Added a `map' function.

  * Various new operators (e.g., string concatenation).

* Expression evaluation is much faster.

* An Emacs mode for editing Nix expressions (with syntax highlighting
  and indentation) has been added.

* Many bug fixes.


Version 0.5 and earlier

Please refer to the Subversion commit log messages.