SoftwareInstallScheme

To have complete control over what versions of the software is being used, I use the following scheme for installing software. All software is installed independent from the Linux distribution, This:

  1. allows installation of newer versions without interfering with other

software on the system,

  1. will prevent any problems occuring from any automatic updates of the Linux distribution and
  1. allows easy rollback to a previous version

All software is installed in a single directory we'll call /topdir in this page. This directory is structured as follows:

/topdir/build: directory for unpacking and building the software packages

/topdir/pkgs: installation directory of the packages

Installing

So to build a software package:

  1. Download it to /topdir/build
  1. Unpack it
  1. Install it under its full name, version number included using e.g. the --prefix flag: 
    ./configure --prefix=/topdir/pkgs/wxWidgets-2.8.1.1

python setup.py install --prefix=/topdir/pkgs/m2crypto-0.17

See below for details on Python installs.

  1. In /topdir/pkgs, create a symbolic link to the version of the package would want to use: 
    ln -s wxWidgets-2.8.1.1 wxWidgets

You can then refer to the software directly (e.g. /topdir/pkgs/wxWidgets/bin/wx-config) A problem (and benefit) of this approach is that not all binaries are in the same directory (cf. /usr), and you cannot set $PATH to a single dir. Hence, there should be a directory /topdir/pkgs/bin that contains links to the relevant binaries. E.g. 

ln -s /topdir/pkgs/wxWidgets/bin/wx-config /topdir/pkgs/bin/wx-config

In cases where a package depends on other packages (i.e., libraries) it may be necessary to set $LD_LIBRARY_PATH to point the right version (and not the Linux distro one). Therefore, /topdir/pkgs/bin may also contain scripts that indirectly access the software. For example, Python depends on the wxWidgets library, so we would create a script /topdir/pkgs/bin/python: 

#!/bin/sh

PYTHONPATH=/prod/pkgs/m2crypto/lib/python2.4/site-packages:"$PYTHONPATH"

PYTHONPATH=/prod/pkgs/wxPython/lib/python2.4/site-packages/wx-2.8-gtk2-unicode:"$PYTHONPATH"

LD_LIBRARY_PATH=/prod/pkgs/openssl/lib:"$LD_LIBRARY_PATH"

LD_LIBRARY_PATH=/prod/pkgs/wxWidgets/lib:"$LD_LIBRARY_PATH"

export LD_LIBRARY_PATH

export PYTHONPATH

/prod/pkgs/Python/bin/python "$@"

Python packages

I consider Python packages as separate software packages. So they are also installed in their own directory in /topdir/pkgs (e.g. /topdir/pkgs/m2crypto-0.17), rather than in the Python installation. To make sure Python finds them, we have to set $PYTHONPATH in the script, as in the example. Note that to make sure you're using the right version of Python when installing, you must install Python packages as follows: 

/topdir/pkgs/bin/python setup.py build

/topdir/pkgs/bin/python setup.py build_ext

/topdir/pkgs/bin/python setup.py install --prefix=/topdir/pkgs/m2crypto-0.17

And also for them, create a symbolic link: 

ln -s /topdir/pkgs/m2crypto-0.17 /topdir/pkgs/m2crypto

Upgrading and Reverting

To upgrade a package, simply install it via the above procedure. Then, carefully, taking into account running processes, replace the symbolic link to the new version: 

ln -sf /topdir/pkgs/m2crypto-0.18 /topdir/pkgs/m2crypto

To revert, just change back the symbolic link to the old version (if the software allows this, e.g. upgraded data formats, etc.)