Help with package managers

[Sean Maguire]

Hi all,

Is it possible to use any of the package managers to find out which
packages have been added since the initial installation? For instance,
I have Ubuntu install on machine A and I want to do a second install
on machine B. I like the package set install on machine A and want the
same on machine B; can I generate a list so that I can "apt-get
install <list>" and have all the packages from machine A installed on
machine B?

Even better would be a way to keep them synchronized, so I install a
package on either machine and the other would detect this and prompt
me to install said package. I guess if it is possible to generate the
list I could get a perl script together to do this.

Cheers for your help,

Sean