Weekly edition	Kernel	Security	Distributions	Contact Us	Search
Archives	Calendar	Subscribe	Write for LWN	LWN.net FAQ	Sponsors

Multiple versions of the same package installed at same time

Posted Nov 13, 2009 12:19 UTC (Fri) by Cato (subscriber, #7643)
Parent article: Python moratorium and the future of 2.x

Perhaps the real issue here is that Linux's excellent package management make it significantly harder to installed a 'second' version of Python, or in fact any package. You either need to compile from source, or install a binary under a tree that doesn't affect the core package, or do a chroot-install, or something else that's equally complex.

Windows often makes this a lot simpler, although sometimes the registry enforces single versions. At least without dependency management it's easier to install the same version twice using a simple installer.

While package management makes things simpler, if there was an easier way to install two versions of Python and choose which applications use which version, you could make a gradual transition to Python 3 without breaking core distro features.

Am I missing something here?

(Log in to post comments)

Multiple versions of the same package installed at same time

Posted Nov 13, 2009 12:49 UTC (Fri) by rahulsundaram (subscriber, #21946) [Link]

Programs have to be designed to be parallel installable. There are applications and libraries which do make this very easy. GTK and gstreamer comes to mind.

Details at http://www106.pair.com/rhp/parallel.html

Multiple versions of the same package installed at same time

Posted Nov 13, 2009 15:49 UTC (Fri) by roblucid (subscriber, #48964) [Link]

Yes, I think you are. Basically if you build an RPM, it does the ./configure; make && make install. Geerally FOSS packages default to /usr/local and distro's configure them to be rooted at /, /usr, /opt whatever.

So in fact you ought to be able to be able to build Gen++ packages, rooted at a different place than Gen, and select which implementation you use by traditional means $PATH & environment.

Opening up openSUSE 11.2 Software Package manager, and I find :

python -2.6.2-6.3
python-32bit -2.6.2-6.2
python3 -3.1-3.3

So perhaps Distro's with good package managers are not the problem at all.
Whoops I just installed python3 without really meaning to, expecting it to tell me about other packages it would require installed to with it.

I have both installed, guessing it'll be python3 :

ladm@fir:~/.kde4/share/config> python3
Python 3.1 (r31:73572, Oct 24 2009, 05:39:09)
[GCC 4.4.1 [gcc-4_4-branch revision 150839]] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

Multiple versions of the same package installed at same time

Posted Nov 13, 2009 16:18 UTC (Fri) by Cato (subscriber, #7643) [Link]

I think you've made my point for me, which was that installing a second
version is significantly more complex than just installing the default
version.

I'm aware that some distros create 'python3' packages, but that's really a
hack rather than a general solution - why isn't it possible to pull a newer
version of Python from a later version of the distro (e.g. Ubuntu 9.10 while
using an earlier version of Ubuntu), and cleanly install it with
dependencies, maybe in a dynamically created chroot or simply a new directory
prefix.

Multiple versions of the same package installed at same time

Posted Nov 14, 2009 17:35 UTC (Sat) by man_ls (subscriber, #15091) [Link]

It is better this way, I think. I don't want a second set of the same libraries lying around; if I did I would do the chroot myself. It does not look like a hack to me, at least on Debian.

# ls -l /usr/bin/python
lrwxrwxrwx 1 root root 9 jul 17 01:48 /usr/bin/python -> python2.5