blog/data/2010-06-16-calling-tasksel.txt

   1 Title: Calling tasksel like the installer, while still getting useful output
   2 Tags: english, nuug, debian
   3 Date: 2010-06-16 14:55
   4
   5 <p>A few times I have had the need to simulate the way tasksel
   6 installs packages during the normal debian-installer run.  Until now,
   7 I have ended up letting tasksel do the work, with the annoying problem
   8 of not getting any feedback at all when something fails (like a
   9 conffile question from dpkg or a download that fails), using code like
  10 this:
  11
  12 <blockquote><pre>
  13 export DEBIAN_FRONTEND=noninteractive
  14 tasksel --new-install
  15 </pre></blockquote>
  16
  17 This would invoke tasksel, let its automatic task selection pick the
  18 tasks to install, and continue to install the requested tasks without
  19 any output what so ever.
  20
  21 Recently I revisited this problem while working on the automatic
  22 package upgrade testing, because tasksel would some times hang without
  23 any useful feedback, and I want to see what is going on when it
  24 happen.  Then it occured to me, I can parse the output from tasksel
  25 when asked to run in test mode, and use that aptitude command line
  26 printed by tasksel then to simulate the tasksel run.  I ended up using
  27 code like this:
  28
  29 <blockquote><pre>
  30 export DEBIAN_FRONTEND=noninteractive
  31 cmd="$(in_target tasksel -t --new-install | sed 's/debconf-apt-progress -- //')"
  32 $cmd
  33 </pre></blockquote>
  34
  35 <p>The content of $cmd is typically something like "<tt>aptitude -q
  36 --without-recommends -o APT::Install-Recommends=no -y install
  37 ~t^desktop$ ~t^gnome-desktop$ ~t^laptop$ ~pstandard ~prequired
  38 ~pimportant</tt>", which will install the gnome desktop task, the
  39 laptop task and all packages with priority standard , required and
  40 important, just like tasksel would have done it during
  41 installation.</p>
  42
  43 <p>A better approach is probably to extend tasksel to be able to
  44 install packages without using debconf-apt-progress, for use cases
  45 like this.</p>