# Release 0.8 (2005-04-11)

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 not 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 --referrers-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