nix (functional package manager)

Nix is a purely functional package manager. This means that it treats packages
like values in purely functional programming languages such as Haskell -- they
are built by functions that don't have side-effects, and they never change
after they have been built. Nix stores packages in the Nix store, usually the
directory /nix/store, where each package has its own unique subdirectory such
as

    /nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/

where b6gvzjyb2pg0... is a unique identifier for the package that captures all
its dependencies (it's a cryptographic hash of the package's build dependency
graph).

Nix may be run in single or multi-user mode (which requires the nix-daemon).
The following sets up multi-user mode.

To have the nix daemon start and stop with your host, add to /etc/rc.d/rc.local:

    if [ -x /etc/rc.d/rc.nix ]; then
      /etc/rc.d/rc.nix start
    fi

and to /etc/rc.d/rc.local_shutdown (creating it if needed):

    if [ -x /etc/rc.d/rc.nix ]; then
      /etc/rc.d/rc.nix stop
    fi

The daemon requires users for building the nix packages, which should be added
under the 'nixbld' group.

    # groupadd -g 314 nixbld
    # for n in $(seq 1 10); do useradd -c "Nix build user $n" \
    #     -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
    #     nixbld$n; done

Restricting access to the daemon is acheived by setting file permissions for
the daemon's socket's folder.

    # groupadd nix-users
    # chgrp nix-users /nix/var/nix/daemon-socket
    # chmod ug=rwx,o= /nix/var/nix/daemon-socket

Correct permissions must also be set for the following profile directories to
give users access.

    # mkdir -p /nix/var/nix/profiles/per-user
    # chgrp nix-users /nix/var/nix/profiles/per-user
    # chmod go+wt /nix/var/nix/profiles/per-user

    # mkdir -p /nix/var/nix/gcroots/per-user
    # chgrp nix-users /nix/var/nix/gcroots/per-user
    # chmod go+wt /nix/var/nix/gcroots/per-user

For setup a user to use nix, add him to the nix-users group and load these
lines on login (via $HOME/.profile):

    export NIX_REMOTE=daemon
    source /etc/profile.d/nix.sh

If you have patches email me, or send a pull request via github:

    https://github.com/PragmaticCypher/nix.SlackBuild
