nix: Added

nix/README

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+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