JFYI
----- Forwarded message from Denis Washington -----
Date: Fri, 18 Jun 2010 10:29:15 +0200
From: Denis Washington
To: rpm-maint@lists.rpm.org
Subject: [Rpm-maint] Announcment: The Psys Library
Hello,
I would like to announce a project to you which aims to attack the
problem of cross-distribution, but distribution-integrated, Linux
software deployment, and might interest you. It is a simple library
written in C, called the "psys library" ("psys" standing for "package
management system"). From the README:
"The psys library provides a simple interface to the system package manager
of a Linux system. It allows installation programs to notify the package
manager of the installation, uninstallation and update of third-party
software packages, and to request these packages to be added to or removed
from the system package database. The psys library interface is generic
and not tied to a specific package management system or Linux distribution.
Note that the psys library is only useful for adding and removing software
which complies to the Linux Standard Base (LSB) specifications [1]. Most
notably, it is assumed that the data files of a software package are
installed into /opt as demanded by the Filesystem Hierarchy Standard (FHS)
[2], and that a package only depends on the interfaces and behavior
specified by the LSB; any additional dependencies must be contained within
the package itself.
The psys library interface is meant to be a proposal for a future version
of the LSB standard."
Those who remember will notice that this is the same idea as the
"Berlin Packaging API" proposal discussed on an LSB Packaging Summit
as part of the LSB face-to-face meeting 2006 in Berlin. The aim was to
bridge the gap between ISVs on the one hand, many of which have
invested in cross-platform installers and would like to use those on
Linux too (instead of having to make not only one, but mulitple
additional packages in various formats for Linux deployment), and
distributors, which would like all software to be centrally managed by
their package manager of choice. By giving installers a way to
communicate with the package manager through a simple,
LSB-standardized library interface, both sides would benefit: ISVs
could use their installer frameworks with only few changes, and
distributors would gain control over software installed by such
installers, integrating it into their package database. There seemed
to be a general agreement at that time that this would be the right
approach to go forward. For more details about what was discussed and
why, see the two-part blog post on this matter by Ian Murdock (who
attended the summit) [1].
Unfortunately, nothing really came out of that. No proof-of-concept
sample implementation was created, leaving the whole concept kind of
in a vaporware state. In 2008, I attempted to change that with a
concrete design and implementation which I named the "Burgdorf
Packaging API" [2]. Unfortunately, it was somewhat over-engineered
(using technologies such as D-BUS, PolicyKit and XML) and would
probably have required a too big amount of code changes to installers;
and while it spawned some discussion (including the thread following
my initial announcement on the LSB packaging mailing list [3], a blog
post by PackageKit creator Richard Hughes [4] and a short OSNews
article [5]), the outcome was, again, nothing.
So now, two years later, I am trying again with the psys library. The
concept stays the same, but the library is much simpler in design and
implementation than Burgdorf. It is now just a simple C function
interface; the complex XML-based metadata format has been replaced by
programmatic definition of the metadata; and adopting installers to
use the API should generally be much less work.
The psys library is not just an idea or general design. There is a
complete implementation, and I have tried my best to document the
library interface as throroughly as possible. The source code and
documentation can be found at the project's page on Gitorious [6].
The library implementation is split into a frontend and a backend
part. The frontend is distribution-independent; it is implemented in
the psys library source code itself. The backend, on the other hand,
is thought to be provided by the distribution (or package manager); it
does the hard work of ensuring that an installation attempted by an
installer is sane (overwrites no files, does not conflict with
installed packages etc) and of adding packages "registered" by an
installer to the system's package database. The core psys library also
supports the concept of "fallback backends", which can be used if the
distribution does not support psys. These fallbacks allow the psys
library to be used *now*, with no distribution-side changes, by
linking it into the installer - this would allow a smooth transition
period until the interface is supported by distributions directly.
Currently, the psys library comes with a fallback backend for
RPM-based distributions (tested successfully on Fedora 13 and openSUSE
11.2).
I am naturally not writing all this to you without reason. I would
like to ask you for help.
* While an RPM fallback backend is already written and seems to work,
I am not particularly fluent with rpmlib, so I might have made some
mistakes. Would somebody like to have a look at the code in order to
make sure it is reasonably correct? I do not want the backend to screw
up any RPM database, so I would be thankful about some additional
eyeballs.
* I would like to know what you think about the psys library and the
concept behind it in general. Could you imagine supporting such an
interface in RPM? Or do you think the idea is fundamentally flawed,
and that RPM should not support cross-distro installers in this way?
I am very interested in your feedback and hope you can help me to make
the vision of easy cross-distribution software deployment on Linux a
reality.
Best regards,
Denis Washington
P.S.: I sent a very similar message to the Debian's dpkg mailing list, too.
History:
[1] http://ianmurdock.com/linux/software-installation-on-linux-today-it-sucks-pa...
[2] http://www.linuxfoundation.org/en/Burgdorf_Packaging_API
[3] https://lists.linux-foundation.org/pipermail/packaging/2008-June/000732.html
[4] http://blogs.gnome.org/hughsie/2008/06/24/lsb-package-api/
[5] http://www.osnews.com/story/19901
Psys Library:
[6] http://gitorious.org/libpsys
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