On the apt-get installation plan

One important aspect of the mancoosi project is to build a model of the installation process in order to simulate packages upgrades before committing the changes on the machine. This work described here and here (and in upcoming publications) relays on the availability installation plan of the meta-installer (the exact order in which packages will be installed, configured and removed ) to run a simulation of maintainers scripts and check for potential problems accordingly to the model.

Thanks to the help of Julian Andres Klode upstream and maintainer of the python-apt bindings it is now possible to extract the installation plan from apt-get without resorting to debug printout or other hacks.

A forthcoming integration with mpm (Mancoosi-Package-Manager, our testbed meta-installer) will give us the possibility to hook the model checker to the meta-installer and to run it before every upgrade.

The two important changes in the python-apt bindings that will make this possible are the new bindings to the class OrderList and the sub-classing of the class package manager. PackageManager .

Regarding the latter, this is a small example (thanks again Julien !) that you can use to get the installation plan as computed by apt-get. In theory, this will also allow to experiment with different back-ends (like rpm - blah ! :) ) easily without the need to hack the c++ code.

import apt_pkg, sys
import apt

class PkgManager(apt_pkg.PackageManager):
        parent = apt_pkg.PackageManager
        depcache = apt_pkg.DepCache(apt_pkg.Cache())
        installionplan = []

        def install(self, pkg, file):
                #print "Installing", pkg.get_fullname(True)
                return True
        def configure(self, pkg):
                #print "Configuring", pkg.get_fullname(True)
                return True
        def remove(self, pkg, purge):
                #print "Removing", pkg.get_fullname(True)
                return True

        def go(self, fd):
              for (p,a) in self.installionplan :
                  if a == "Inst" or a == "Conf" :
                      ver = self.depcache.get_candidate_ver(p)
                  else :
                      ver = p.current_ver
                  print a, p.name, ver.ver_str, ver.arch

              return True

apt_pkg.PackageManager = PkgManager

cache = apt.Cache()
pkg = cache["python"]
if pkg.is_installed:


print "COMMIT"  

And this is the result on my machine :

abate@zed.fr:~$python pkgmanager-test.py
Reading package lists... Done
Building dependency tree      
Reading state information... Done
Rem alacarte 0.13.2-1 all
Rem apt-listchanges 2.85.7 all
Rem apt-xapian-index 0.41 all
Rem gnome-accessibility 1:2.30+7 all
Rem gok 2.30.0-1 amd64
Rem dasher 4.11-1 amd64
Rem gnome-orca 2.30.2-2 all
Rem python-pyatspi 1.30.1-3 all
Rem at-spi 1.30.1-3 amd64
Rem bluetooth 4.91-1 all
Rem gnome-bluetooth 2.30.0-2 amd64
Rem bluez 4.91-1 amd64
Rem brasero 2.30.3-2 amd64
Rem gthumb 3:2.13.1-1 amd64
Rem libbrasero-media0 2.30.3-2 amd64
Rem brasero-common 2.30.3-2 all
Rem bzr 2.3.1-2 all
Rem gnome-core 1:2.30+7 amd64
Rem gnome-control-center 1:2.30.1-3 amd64
Rem capplets-data 1:2.30.1-3 all
Rem cheese 2.30.1-2 amd64
Rem cheese-common 2.30.1-2 all
Rem cython 0.14.1-5 amd64
Rem dasher-data 4.11-1 all
Rem deluge 1.3.1-1 all
Rem deluge-gtk 1.3.1-1 all
Rem deluge-common 1.3.1-1 all
Rem deskbar-applet 2.32.0-1+b1 amd64
Rem dia 0.97.1-8 amd64
Rem dia-common 0.97.1-8 all
Rem doxygen 1.7.4-1 amd64
Rem doxygen-latex 1.7.4-1 all
Rem dput all
Rem duply all
Rem duplicity 0.6.13-1 amd64
Rem edos-debcheck 1.0-9 all
Rem edos-distcheck 1.4.2-12 amd64
Rem eog 2.30.2-1 amd64
Inst libxp6 1:1.0.1-1 amd64
Inst lesstif2 1:0.95.2-1 amd64
Inst xpdf 3.02-12 amd64
Conf libxp6 1:1.0.1-1 amd64
Conf lesstif2 1:0.95.2-1 amd64
Conf xpdf 3.02-12 amd64
[ ... ]

Average: 2.4 (25 votes)


Good post. It really help me

Good post. It really help me understand the basics of the apt module. Its been really difficult to find working examples

Thank you very much for this

Thank you very much for this example, very helpful.