Motivation
==========

The primary motivation behind pkgix was a restricted environment (no root
access, e.g. compute cluster) without specific software dependencies.
Furthermore, the dependencies should be the same across a variety of machines
(e.g. local workstation). In particular:

* require specific version of software, with many dependencies;
* restricted permissions;
* little storage space available;
* the now common language-specific package managers do not help;
* this has to happen on several machines.

Typically, one resorts to many instances of ``./configure && make && make
install`` (or equivalent for whatever software we need); the next best thing is
a collection of scripts to automate this.  Now consider the problem of keeping
this collection of software up-to-date and we might as well give up. The
solution we really want is a package manager.

Although package management appears to be a solved problem, none of the
existing solutions seem to address all of the issues that initially sparked
creation of pkgix.  The goal was to require as few dependencies as possible,
i.e. BASH and a minimal set of external tools---in addition, the package
manager should:

* be able to install in an arbitrary prefix (no root!).
* resolve dependencies automatically;
* if, however, a dependency is already installed on the target system it will
  mark it as satisfied;
* provide the ability to upgrade, uninstall, and do general maintenance on a
  prefix;
* combine prefixes.

Related Software
----------------

* `LinuxBrew <https://github.com/Homebrew/linuxbrew>`_: Port of Homebrew to
  Linux.
* `Gentoo Prefix <https://wiki.gentoo.org/wiki/Project:Prefix>`_: Port of
  Gentoo packages to work with arbitrary prefixes.
* `NixOS <http://nixos.org>`_: Unfortunately requires root access to set up.

The main issue with the above is that they pull a large number of dependencies
that are usually already available on the user's system, yet still install them
needlessly (using up unnecessary space). One of the main goals of pkgix is to
reuse as many dependencies already present on the user's system---to do this,
several features were added to make this simpler (metapackages which
dynamically resolve to either another package or say they are satisfied).