automagic way to (re-)install all packages on a system?

[Mario Vukelic]

On Wed, 2007-09-19 at 16:30 -0700, Jeff.Hodges at KingsMountain.com wrote:
> Here's a scenario..
> 
> I'm wondering if there's an automagic way to re-install all packages that are 
> installed on a given "source" system -- e.g. have synaptic or aptitude write 
> out a file of a system's current set of installed packages, then be able to do 
> an ubuntu install on a new "target" system, say, and then feed that file to 
> synaptic/aptitude/whatever, and have all the packages that'd been installed on 
> the source system installed on the target system.

man dpkg:

To make a local copy of the package selection states:
	dpkg --get-selections > myselections

You might transfer this file to another computer, and install it there
with:
	dpkg --clear-selections
	dpkg --set-selections < myselections

Note  that  this will not actually install or remove anything, but just
set the selection state on the requested packages. You will need some
other application to actually download and install the requested
packages. For example, run dselect and choose "Install". [Or rather,
nowadays: aptitude. Most likely the interactive mode is best for this:
just run "aptitude" on the cmd line without any arguments]